Polyvinylchloride-based Blends: Preparation, Characterization and Applications (Springer Series on Polymer and Composite Materials) 3030784541, 9783030784546

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Springer Series on Polymer and Composite Materials

Visakh P. M. Raluca Nicoleta Darie-Nita   Editors

Polyvinylchloride-based Blends Preparation, Characterization and Applications

Springer Series on Polymer and Composite Materials Series Editor Susheel Kalia, Army Cadet College Wing, Indian Military Academy, Dehradun, India

The “Springer Series on Polymer and Composite Materials” publishes monographs and edited works in the areas of Polymer Science and Composite Materials. These compound classes form the basis for the development of many new materials for various applications. The series covers biomaterials, nanomaterials, polymeric nanofibers, and electrospun materials, polymer hybrids, composite materials from macro- to nano-scale, and many more; from fundamentals, over the synthesis and development of the new materials, to their applications. The authored or edited books in this series address researchers and professionals, academic and industrial chemists involved in the areas of Polymer Science and the development of new Materials. They cover aspects such as the chemistry, physics, characterization, and material science of Polymers, and Polymer and Composite Materials. The books in this series can serve a growing demand for concise and comprehensive treatments of specific topics in this rapidly growing field. The series will be interesting for researchers working in this field and cover the latest advances in polymers and composite materials. Potential topics include, but are not limited to: Fibers and Polymers: • • • • • • • • • • •

Lignocellulosic biomass and natural fibers Polymer nanofibers Polysaccharides and their derivatives Conducting polymers Surface functionalization of polymers Bio-inspired and stimuli-responsive polymers Shape-memory and self-healing polymers Hydrogels Rubber Polymeric foams Biodegradation and recycling of polymers

Bio- and Nano- Composites:• • • • • • • • •

Fiber-reinforced composites including both long and short fibers Wood-based composites Polymer blends Hybrid materials (organic-inorganic) Nanocomposite hydrogels Mechanical behavior of composites The Interface and Interphase in polymer composites Biodegradation and recycling of polymer composites Applications of composite materials

More information about this series at http://www.springer.com/series/13173

Visakh P. M. Raluca Nicoleta Darie-Nita •

Editors

Polyvinylchloride-based Blends Preparation, Characterization and Applications

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Editors Visakh P. M. Faculty of Electronic Engineering, Department of Physics Electronics TUSUR University Tomsk, Russia

Raluca Nicoleta Darie-Nita Physical Chemistry of Polymers Department “Petru Poni” Institute of Macromolecular Chemistry Iasi, Romania

ISSN 2364-1878 ISSN 2364-1886 (electronic) Springer Series on Polymer and Composite Materials ISBN 978-3-030-78454-6 ISBN 978-3-030-78455-3 (eBook) https://doi.org/10.1007/978-3-030-78455-3 © Springer Nature Switzerland AG 2022 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

This book on Polyvinylchloride (PVC)-based Blends: Preparation, Characterization and Applications covers many of the recent research accomplishments in the area of PVC-based blends. Throughout the book, various topics are addressed, such as the current state of the art of PVC-based blends, new challenges, and opportunities. An emphasis is given to the types and sizes of components/fillers and optimum compositions of PVC blends, their processing and structure-properties relationships, modification/compatibilization methods, and possible applications. The current book is a valuable reference source for university and college faculties, professionals, postdoctoral research fellows, senior graduate students, and researchers from R&D laboratories working in the area of PVC-based blends. Prominent researchers from industry, academia, and government/private research laboratories across the globe gave their contributions for the chapters within this book. Chapter 1 provides an introduction to the area of PVC blends, along with their compositions, preparation methods, applications, new challenges, and opportunities of this field. Chapter 2 offers a review on the structure–properties relationships for PVC. Characterization techniques of PVC/thermoplastic nano-blends are discussed in Chap. 3, while Chap. 4 deals with the applications of PVC/thermoplastic nano-, micro-, and macro-blends, including structural uses, packaging, military, and/or aerospace applications. The factors affecting the properties of PVC nano-, micro-, and macro-blends are covered in Chap. 5, with emphasis on mechanical properties, thermal stability, and electrical properties. Interface modifications and compatibilization of PVC nano-, micro-, and macro-blends are discussed in Chap. 6. Chapter 7 presents examples of bio-based plasticizers for PVC, authors covering several aspects such as recent progress in performance of PVC plasticizers as alternative to DEHP, petroleum-derived PVC plasticizers, green plasticizers for PVC, and PVC/compatible additives. Chapter 8 deals with PVC/polysaccharide blends, in particular describing the processing, compatibilization, and properties of PVC blends with several types of polysaccharides such as chitosan, cellulose, and starch. Chapter 9 of this book covers PVC membranes preparation, mathematical modeling, characterization, modification, v

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and applications. Recent studies on bio-based PVC-related blends are summarized in the final chapter, the authors focusing on PVC bio-related nano-blends and bio-based blends of PVC with polyesters, polysaccharides, natural fillers, and poly (vinyl alcohol) (PVA). Finally, the editors would like to express their sincere gratitude to all the contributors of this book, who provided excellent commitment and support to the successful completion of this venture. We would like to thank all the reviewers who have taken their valuable time to make critical comments on each chapter. We also thank the publisher Springer for recognizing the demand for such a book and for realizing the increasing importance of the area of Polyvinylchloride (PVC)-based Blends: Preparation, Characterization and Applications. Tomsk, Russia Iasi, Romania

Dr. Visakh P. M. Dr. Raluca Nicoleta Darie-Nita

Contents

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Polyvinylchloride (PVC)-Based Blends: State of Art, New Challenges and Opportunities . . . . . . . . . . . . . . . . . . . . . . . . . P. M. Visakh and Raluca Nicoleta Darie-Nita Polyvinylchloride (PVC): Structure and Properties Relationship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shahzad Maqsood Khan, Nafisa Gull, Rafi Ullah Khan, and Muhammad Taqi Zahid Butt

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Characterization Techniques of Polyvinylchloride (PVC)/Thermoplastic Nano-Blends . . . . . . . . . . . . . . . . . . . . . . . . . Shweta Sharma, Ankush Parmar, and S. K. Mehta

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Applications of Polyvinylchloride (PVC)/Thermoplastic Nano-, Micro- and Macroblends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Elena Grosu

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Factors Affecting the Properties of Polyvinylchloride (PVC) Nano-, Micro- and Macro-Blends . . . . . . . . . . . . . . . . . . . . . . . . . . Anca Andreea Ţurcanu

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Interface Modification and Compatibilization of Polyvinylchloride (PVC) Nano-, Micro- and Macro-Blends . . . . . 111 Anca Andreea Ţurcanu

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Bio-Based Plasticizers for Polyvinylchloride (PVC) . . . . . . . . . . . . . 137 Maria Râpă, Raluca Nicoleta Darie-Nita, Ecaterina Matei, and Andra Mihaela Predescu

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Polyvinylchloride (PVC)/Polysaccharides Blends . . . . . . . . . . . . . . . 159 Andrzej Iwanczuk and Joanna Ludwiczak

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Preparation of Polyvinylchloride (PVC) Membranes, Characterization, Modification, Applications, and Mathematical Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 Heba Abdallah and Ayman El-Gendi

10 Bio-Based Polyvinylchloride (PVC)-Related Blends . . . . . . . . . . . . . 211 Raluca Nicoleta Darie-Nita, Maria Râpă, and P. M. Visakh

About the Editors

Dr. Visakh P. M. (MSc, MPhil, PhD) is a prolific editor with more than 38 books already published. Now, he is working as Associate Professor in TUSUR University, Tomsk, Russia, since 2017. He did his postdoctoral research in Tomsk Polytechnic University, Tomsk, Russia (2014–2017). He obtained his PhD, MPhil, and MSc degrees from School of Chemical Sciences, Mahatma Gandhi University, Kottayam, Kerala, India. He edited 38 books from Scrivener (Wiley), Springer, Royal Society of Chemistry, Elsevier, and more than 25 books in press, (from Wiley, Springer, Royal Society of Chemistry, and Elsevier). He has been invited as a visiting researcher in Russia (2014 to present), Portugal (2013 and 2014), Czech Republic (2012 and 2013) Italy (2009 and 2012), Argentina (2010) Sweden (2010, 2011, and 2012), Switzerland (2010), Spain (2011 and 2012), Slovenia (2011), France (2011), Belgium (2012), and Austria (2012) for his research work. He has visited 12 countries; he has visited 15 universities in Europe. He has published 20 publications, 4 reviews, and more than 30 chapters. He has attended and presented more than 28 conferences, he has 1829 citations, and his h-index is 20. He acts as a guest editor for four international journals.

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About the Editors

Dr. Raluca Nicoleta Darie-Nita (M.Sc., Ph.D.) is currently Senior Researcher at “Petru Poni” Institute of Macromolecular Chemistry, Iasi, Romania. She received her PhD in Chemistry (2009) and Postdoctoral degree in Biomaterials (2013) from the Romanian Academy. MSc in Organic Physical Chemistry (2001) and license in Chemistry and Physics (1999) were awarded by Faculty of Chemistry, “Al. I. Cuza” University of Iasi, Romania. She has over 20 years of experience in reactive processing (natural and synthetic, pure or recycled polymers), polymers compatibilization and chemical functionalization, physico-chemical characterization of polymers and composites, development of materials for food packaging and structural applications, and durability testing of plastic materials. She has published 66 papers (56 ISI), 1 book, 11 chapters, and has 3 patents (1 international). She is also a member of national and international grants (director for 2 national grants) and has attended over 150 conferences, giving oral and poster presentations. The high visibility of her scientific activity is reflected in more than 1100 citations, and H-index = 19 (Web of Science). She serves as guest editor for two international journals.

Chapter 1

Polyvinylchloride (PVC)-Based Blends: State of Art, New Challenges and Opportunities P. M. Visakh and Raluca Nicoleta Darie-Nita

Abstract PVC is a versatile polymer used in a diversity of applications, function of its own, as well as its blending component’s properties. Since the early 1930s, when commercial production of PVC started, it became a universal polymer due to its high performance and low cost, combined with the broad range of items that can be obtained by multiple processing techniques and variable parameters. For enhanced performances, PVC can be mixed with (bio)plasticizers, thermoplastics, rubbers, polysaccharides, minerals, natural fillers or other types of additives in order to improve PVC blends compatibility. PVC is found in various applications, such as building, packaging, automotive, military and aeronautic industries, medicine, ships construction, life rafts, garden hoses, swimming rings, footballs, toys, different cards and so on. PVC is also used in the preparation of membranes (e.g., for water treatment), owing to its good mechanical strength, abrasion resistance, chemical stabilization, thermal properties, low cost and corrosion resistance. Different factors affect the properties of PVC composites, such as processing techniques and parameters, the origin of the filler, its particle size and its aspect ratio, as well as its concentration and the homogeneity of its distribution in the polymer matrix. PVC bionanocomposites can be also produced by using nanoelements resulted from different renewable resources, e.g., cellulose, starch, chitin, inducing also PVC’s biodegradability.







Keywords Polyvinylchloride Structure Properties Applications Blends Plasticizers Biocomposites











Compatibility


P. M. Visakh (&) Department of Physical Electronics, TUSUR University, Vershinina Street, 74, 634050 Tomsk, Russia R. N. Darie-Nita Physical Chemistry of Polymers Department, “Petru Poni” Institute of Macromolecular Chemistry, 41A Gr. Ghica Voda Alley, Iasi, Romania © Springer Nature Switzerland AG 2022 V. P. M. and R. N. Darie-Nita (eds.), Polyvinylchloride-based Blends, Springer Series on Polymer and Composite Materials, https://doi.org/10.1007/978-3-030-78455-3_1

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PVC: Structure and Properties Relationship

Commercial production of PVC has been initiated in Germany in the early 1930s, via emulsion polymerization. The heat stability and processing of PVC were firstly improved in 1932 when the plasticizers for PVC were discovered by Semon, the use of stabilizers being developed in 1930s [1]. Polymerization of vinyl chloride takes place by a free radical addition process, comprising four elementary reactions: initiation, propagation, chain transfer to monomer and bimolecular termination steps. PVC resin can be produced by the following mostly used methods: solution, bulk, emulsion and suspension polymerization. PVC became a universal polymer due to its high performance and low cost, combined with the broad range of items that can be obtained from multiple processing techniques and parameters [2]. Flexible products like artificial leather can be realized from PVC obtained by emulsion polymerization. PVC powder can be combined with plasticizer resulting plastisol, which turn into plastigel by heating. The rheology of plastisol is highly influenced by the type, amount and molecular mass of emulsifier, particle size distribution and mean particle size of PVC [3, 4]. As neat PVC is a brittle and inflexible material with low commercial possibilities, and it requires additives for enhancing its applications. PVC degrades severely under high pressure and heat, at processing temperature of around 150 °C, hydrogen chloride being eliminated and color changes from white to yellow, then brown, turning finally black [5, 6]. Due to its excellent electrical properties, PVC is used in extensive electrical applications, especially for easily molded insulators. Structural features, chemical composition and the degree of molecular order are influencing the electrical properties of PVC. The dielectric properties of PVC offer a description of the hopping and rotating process of electrons involved in PVC and explain the phenomenon of dispersion related to its molecular configuration and ordering, as it influences the material’s conductivity [7]. PVC is used as an insulating material in many electrical appliances, wire and cables. Several tests are used to determine the effect of formulation variables on this insulating property, namely (1) resin conductivity (2) volume resistivity and (3) insulation resistance. Optical properties are very important and refer to polarization, interface, antireflection and reflection properties [8]. Optical absorption studies provide details on the type of optical transitions, localized states and electronic band structures, making these materials striking for chemical sensors for detecting ionic species and display panels [9–12]. When evaluating thermal property of PVC, glass transition temperature Tg is very important, representing the temperature at which PVC changes from a hard or glassy state to a soft, rubbery state [13]. Characteristic thermal transitions can be recorded for PVC by differential scanning calorimetry (DSC). As formed in typical commercial process, PVC is very amorphous, with very low crystallinity degrees.

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A crystalline PVC can be synthesized if the order is forced by polymerization conditions, such as extremely low reaction temperatures (−50 to −100 °C). When the polymer chain has no order or random order, it is called atactic, and PVC generally falls into this category. The melting point of fully syndiotactic PVC reported in the literature is about 400 °C [14], but such a perfectly syndiotactic polymer has not yet been synthesized. PVC has a high chlorine content, but considering all the progress, there are several future demands for long-term development and research in the PVC industry, e.g., for the production of non-toxic plasticizer, without metal, non-toxic stabilizer, to overcome the possibility of replacing PVC with other polymers, e.g., by thermoplastic elastomers. Due to its properties, PVC can be used in many applications, including building industry: cables ducting and conduits, guttering, potable and gravity pipes, window frames and doors, roller shutters, sheets and panels, reservoir linings, wall covering, flooring, sports stadium seats, etc. Identity cards, smart cards, credit cards and telephone cards are made up from PVC nowadays. Ships’ construction, liferafts, garden hoses, swimming rings, footballs and toys are also made up of PVC.

1.2

Characterization Techniques of PVC/Thermoplastic Nanoblends

Adding a thermoplastic polymer, an elastomer or wood flour to the PVC together with nanofiller can significantly improve the properties of PVC. The addition of mineral nanofillers to macro-molecular organic mixtures, including PVC, led to polymeric nanocomposites characterized by low weight, low costs and improved properties. A second polymer can cover the surface of the nanofiller particles by increasing the interaction between the PVC-nanofiller [15, 16]. Various techniques can be used for a comprehensive assessment and characterization physico-chemical properties of PVC blends (i.e., stereochemistry, particle size distribution profile, surface charge, morphology and surface geometry, thermal and mechanical properties, etc.). Several PVC/MMT and PVC/Na-MMT nanocomposites have been prepared by Madaleno et al. [17] via solution blending and solution blending coupled with melt compounding methodology. Morphological, thermal and mechanical characteristics of the formulated nanocomposites were evaluated. TGA analysis was used to follow the thermal behavior of pristine PVC and PVC-based nanocomposites and PVC/Na-MMT nanocomposites showing enhanced thermal stability over PVC/ OMMT nanocomposites and pristine PVC. Chipara et al. [18] prepared polyvinylchloride-single-walled-carbon nanotube composites (PVC-SWNTs) and investigated the thermal and spectroscopic properties of the formulated nanocomposites. DSC studies were performed to envisage the intermolecular interactions between PVC and nanofillers, and an increase in the

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glass transition temperature (Tg) of the polymeric matrix with the loading of PVC-SWNTs is being recorded. A two-step reaction was employed by Mondragon et al. [19] to realize PVC/Poly (e-caprolactone) (PCL)/organophilic montmorillonite (OMMT) and PVC/ Polylactide (PLA)/OMMT nanocomposites. The morphological properties of the nanocomposites were investigated by atomic force microscopy. Well-dispersed MMT particles within the corona or the polymeric matrix of all the nanocomposites containing 3% w/w clay were clearly revealed by AFM images. Clay dispersion and adhesion between MTT and polymeric matrix affected also the tensile strength and stiffness of the studied nanocomposites. Transmission electron microscopy (TEM) coupled with bright field emission was employed for the morphology characterization of PVC/organically modified clays (nanofillers), viz. hectorite and bentonite nanocomposites prepared by Awad et al. [20]. TEM analysis demonstrated that hectorite and bentonite were in a well-dispersed nanosized state and by the content of plasticizer and dispersant affected the dispersion of nanofillers within the polymeric PVC matrix. Gao et al. [21] investigated PVC nanocomposites intercalated with vinyl grafted polyhedral oligomeric silsesquioxanes containing methylacrylopropyl groups (PVC/V-POSS). The rheological behavior of nanocomposites was evaluated by torque and capillary rheometry, following the effect of blend, shear rate and shear stress on non-Newtonian index. Mathur et al. [22] performed the structural characterization of cadmium sulfide (CdS)-embedded polystyrene/polyvinylchloride (PS/PVC) nanocomposites (CdS-PS/PVCnc) using small-angle X-ray scattering (SAXS) to evaluate the nano range dispersion in the composites. The SAXS analysis revealed that the CdS-PS/PVCnc showed a higher scattering intensity when contrasted with their counterparts without CdS-dispersed specimens.

1.3

Applications of PVC/Thermoplastic Nano-, Microand Macro-Blends

PVC is widely used due to its good processability, low flammability and low cost. Its low thermal stability during melt processing is considered a drawback, but it can be ameliorated by incorporation of stabilizers and other processing additives. Various natural or synthetic inorganic nanofiller compounds have been added to PVC in order to improve their mechanical strength properties or to reduce cost. Majority of micro-, nano- and macro-blends of PVC contain mainly polymethyl methacrylate (PMMA), polystyrene (PS), acrylonitrile butadiene styrene (ABS), ethylene–vinyl acetate (EVA) copolymer and other thermoplastic resins, together with plasticizers such as phthalates, citrates, adipates, nano-, micro- and macro-inorganic/organic fillers (e.g., calcium carbonate or kaolin), organic fillers (e.g., soy bean flour, wood flour (hard and soft), nutshell hull and flour, natural fibers) in concentration of 40–65 wt%.

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PVC has gained more attention and influence in the industry and trading, due to its combination with other polymers and performance of nano materials, together with increasing demand of replacing wood, paper and metallic parts in several domains such as packaging, construction, military and aerospace applications. Various recipes of PVC were realized, improved and tested before their applications in packaging, parts of airplanes/helicopters, structural components of building construction, or in optical devices. An increased attention was given to PVC nano blends to be used in packaging applications, i.e., PVC/montmorillonite materials [23, 24]. Among different polymers such as polyethylene (PE), polypropylene (PP), polyvinyl acetate (PVA), polyvinyl alcohol (PVOH), polyethylene terephthalate (PET), polyamide (PA), etc., PVC can be used as the main polymer in nanoblends and offer good properties of melt processing in various desired shapes of food packaging [25]. The influence of nanosized filler dopant salt, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) on the rheological properties of a blend electrolyte with ratio of 70 wt% of PMMA to 30 wt% of PVC was evaluated by Liew and Ramesh [26]. PVC nanoblends can be processed to realize specific materials with improved characteristics for military application by using inorganic fillers to increase electrical conductivity, improve resistance to heat or ultraviolet light, as well as reducing cost. For aerospace applications, PVC nanoblends can be used in: interior components, technical parts, structural elements as well as components for navigation, propulsion engineering and satellite technology. Before PVC nanoblends are approved for aviation and aerospace applications, they must normally be tested for components and semi-finished products such as rods, sheets and tubes. PVC micro-blends can be used in specific materials that lead to innovations for fast, high-quality construction to improve aesthetics and increase work speed [27]. Although PVC has poor thermal stability, low impact strength and high melt viscosity of its applications in several industries were enlarged by several modifications of PVC [28], together with incorporation of plasticizers and elastomers [29]. PVC macro-blends are applicable to manufacture some interior or exterior parts of aircrafts, such as dashboard enclosures, radomes/nose cones, beverage carts, counter backsplashes, ceiling and wall panels and partitions, flooring, signage, video bezels, various seating parts, window reveals, shades and dust panes, components and box of sanitary kit, and equipment housings.

1.4

Factors Affecting the Properties of PVC Nano, Microand Macro-Blends

Amount influence of mineral fillers like alumina oxide, mica, calcium carbonate used on PVC/(a-MSAN)/(CPE) blend was studied by Zhang et al. [30]. With the increase in mineral amount, the tensile strength decreases due to a low interfacial

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interaction between the polymer matrix and filler. This was also confirmed by Bishay et al. [31] who used alumina filler for PVC blends and found that the increase in alumina powder (0–40 wt%) led to a decrease in elongation at break, due to the discontinuities in the structure of the PVC/Al blends. Jazi et al. [32] studied the effect of mass ratios of modified micro/nano-CaCO3 particles in PVC/ surface-modified CaCO3 blends on the mechanical properties of the composites. Arayapranee et al. [33] studied the possibility of improving the mechanical properties of PVC blends by the combination of PVC with elastomers; therefore, they modified natural rubber by graft copolymerization with styrene and MMA using a batch emulsion polymerization process. Ratman et al. [34] studied 50/50 PVC/ENR blends with different amounts of tribasic lead sulfate to see how the filler influenced the tensile strength of the blends, which were also irradiated using a 3.0 meV electron accelerator with doses from 0 to 200 kGy. Ward et al. [35] used graphite and copper nanoparticles as fillers and showed that with the increase in filler concentration, the tensile strength values decrease. Yuan et al. [36] found that with the increase in CB loading, the tensile strength of the high-density polyethylene matrix also increases. When compared to the PVC/PEO/ CB blends, the ones with PEGDE have lower tensile strength, because the addition of the PEGDE leads to a decrease in the stiffness of the blend caused by the replacement of interaction between the polymers with ones with the surface modifier. As showed by Abu-Abdeen and Elamer [37] in their work, the increase in PVC amount from 0 to 80 phr in PVC-NBR vulcanized with 40 phr carbon black nanopowder nano blends leads to increase in elastic modulus (Young’s modulus), but the increase in PVC amount led to a decrease in abrasion resistance, elongation at break, the maximum degree of swelling and penetration rate. Another team [38] studied how using graphite filler in PVC/PEO blends affected the conductivity and mechanical properties of this blends. They found that with the addition of graphite to PVC/PEO blends, Young’s modulus values of PVC/PEO/graphite decrease and keep this tendency as the graphite loading increases, because of the deformation effect of graphite on the molecular chains in the polymer blend leading to reduced mobility. PVC/CaCO3 blends were studies by Guermazi et al. [39] which showed that with an increase in filler amount from 20 to 40% CaCO3, the elongation at break displays an obvious decrease. This can be attributed to a weaker interfacial adhesion between the polymer matrix and the filler because when the filler amount increases, the risk of formation of more aggregates is higher which are failure-initiation sites and lead to more stress concentration around dispersed CaCO3 filler particles. Esmizadeh et al. [40, 41] obtained PVC-NBR nanoblends by melt-mixing in a Brabender plastograph in which a self-cross-linking reaction occurs. The extent of cross-linking reaction increases with an increase in mixing parameters such as mixing and processing temperature, as well as on the rotor speed used. Bishay et al. [31] studied the influence of aluminum content on the hardness of PVC/aluminum (Al) micro-blends and found that with an increase in Al content from 0 to 40 wt%,

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the shore A hardness slightly decreased due to a weak interfacial adhesion between the polymer matrix and Al filler [42].

1.5

Interface Modification and Compatibilization of PVC Nano-, Micro- and Macro-Blends

Interface modification of polymers is a mechanical–physical–chemical process of realizing the compatibilization between two or more components in order to tailor the final material’s properties for various practical applications like sensors, actuators and electrodes [43–45], nano- and ultrafiltration membranes [46, 47], advanced building materials with improved photo-aging and flame retardant properties [48], nanocomposites with antibacterial properties and other biocompatible materials with medical use [49–53], and even pyrotechnic signaling compositions [54, 55]. From the mechanical studies, it was observed that with increase to 15 wt% of EVA-g-MAH concentration, the PVC/PA11 blends achieve maximum values for tensile modulus, tensile strength, elongation at break and impact strength. Above 15 wt%, the EVA-g-MAH excess is immiscible with PA11, leading to a decrease in compatibilization and mechanical properties. Niu and Li [56] studied the in situ compatibilization of PVC/polystyrene (PS) blends catalyzed by anhydrous aluminum chloride. They investigated the structure of PVC/PS blends by means of FTIR and the properties by means of mechanical tests, SEM and DSC analysis. Asadinezhad et al. [57] added a coating of polysaccharides on medical-grade PVC, evaluating the surface characteristics and the extent of bacterial adhesion. Surface chemistry is the main factor that determines most of the polymer surface properties. It basically refers to the molecular structure and organization on the surface that is also a measure of the tendency of the substance to undergo surface reactions. The formation of co-cross-linked product at the PVC/PE interface was confirmed to be very important for the final product properties. Xu and his team [58] studied the influence of NBR (content of acrylonitrile 33.5–36.5 wt%) on the properties of PVC/ low-density polyethylene (LDPE) blends and also the synergism with cross-linking agent. Novel PVC/silica–lignin blends were synthesized and characterized by Klapiszewski et al. [59] by means of thermal analysis (TGA), morphology (optical microscopy and SEM) and mechanical properties. It is well known that the structure of blended materials determines their properties, especially such structural factors like bonding strength on the interface between the dispersed phase and polymer matrix, shape of dispersed phase inclusions and homogeneity of filler particle distribution in the polymer matrix. Eastwood and Dadmun [60] studied multiblock or blocky distributed chlorinated polyethylene (bCPEs) ability to strengthen PVC/POE interface in comparison to that of randomly distributed chlorinated polyethylene (rCPE), by means of asymmetric double cantilever beam, peel test experiments, XRD and DSC analysis.

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Biobased Plasticizers for PVC

Over 95% of all of the medical PVC is used to manufacture bags for storage of blood and blood components, endotracheal tubes, catheters, drains, connectors used in hemodialysis, hemofiltration, autotransfusion, surgery, anesthesia and intensive care [61]. The value of PVC for use in medical applications is given by its: flexibility; chemical stability and possibility of sterilization; low cost and availability; biocompatibility with the human body. The literature reported that phthalates represent more than 85% of world plasticizers production, out of which 90% is annually used in PVC manufacturing [62]. They are used in amount of maxim 40% from the overall material. In addition, PVC materials containing DEHP represent a problem also from the perspective of environmental protection. They are slowly biodegraded in the environment, so it is impossible to be recycled, and during combustion of the PVC waste, dioxin is produced. However, eco-friendly bioremediation of phthalates from medical devices has been largely studied. Thereby, three mycelial fungi, Aspergillus parasiticus, Fusarium subglutinans and Penicillium funiculosum, were found able to completely consumed intact DEHP physically bound to blood storage bags made from PVC [63]. The increased interest in the development of biobased plasticizers for PVC is related to the plasticizers synthesized from: biorenewable plant oils (e.g., rice fatty acid, soybean oil [64], hydrogenated castor oil, camphor [65]), agricultural by-products (e.g., sugar cane [66], glucose [67]) and waste (e.g., cooking oil [68, 69]). The synergetic effect of epoxidized soybean oil (ESBO) on hydrogenated castor oil plasticizer was demonstrated by investigation the plasticizer migration, tensile properties and dynamic friction of plasticized PVC films. The main application of these materials is for the wire and cable manufacturing industry. A series of bioplasticizers for PVC based on a renewable monomer derived from glucose, isosorbide diesters, with different alkyl chain length, namely isosorbide dibutyrate (SDB), isosorbide dihexanoate (SDH), isosorbide dioctanoate (SDO) and isosorbide didecanoate (SDD) have been successfully prepared by Yang et al. [70]. An epoxidized glycidyl ester of soybean oil fatty acids (EGESOFa) has been obtained by Chen et al. [71] as an efficient alternative plasticizer for manufacturing PVC products to satisfy the health, food safety and environmental demands. Li et al. [72] designed and produced PVC tissue mimicking material for needle insertion by adding mineral oil and micro-sized glass beads to the PVC polymer. They conducted a factorial design of experiment by changing three factors; the ratio of softener and PVC polymer solution, the mass fraction of glass beads and the mass fraction of the mineral oil.

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PVC/Polysaccharides Blends

Cellulose, chitin/chitosan, starch and glycogen are several of the most popular polysaccharide materials used in blends with PVC. Bigot et al. [73] grafted seaweed antibacterial polysaccharides onto PVC surfaces using an original click chemistry pathway. PVC isothiocyanate surfaces (PVC–NCS) were first prepared by nucleophilic substitution of the chloride groups by isothiocyanate groups. Sobahi and his team [74] prepared carrier-mediated blends of chitosan with PVC using nanoparticles of dithizone and utilization of different solvents to optimize the homogeneous mixing of the blend components. The obtained blends were found to have reasonable extent of compatibility. Such compatibility depends mainly on the way how the components have been blended with each other. The polymer-supported dithizone was investigated toward its ability to be used for removal of some metal ions from their aqueous solutions. Badr et al. [75] have utilized heparin-modified chitosan (H-chitosan) membrane to enhance biocompatibility of sodium selective membrane electrode based on the highly thrombogenic PVC. Xu et al. [76] used chitosan as interface self-reinforcing and antibacterial agent in modified PVC-based wood flour composites to improve the interface adhesion as well as endow a novel antibacterial function to wood flour (WF)/PVC composites. Chitosan (CS) was found as a novel coupling agent for PVC composites with wood flour (WF/PVC) that improved interfacial adhesion. Xu et al. in their study [77] aimed at investigating the effects of adding chitosan of varied addition amounts and particle sizes on thermal and rheological properties of PVC/WF composites. Antibacterial activity is another CS feature that has been observed [78]. Based on the results of FTIR, SEM and DMA analysis, the ability for interface self-reinforcement of CS has been revealed. Exposure of PVC/WF/CS composites to moisture for long term resulted in significant increase in water absorption. There has been sufficient antibacterial activity observed when adding the certain amount of CS to compound. Djidjelli et al. [79] prepared composites using PVC as a polymer matrix and 10, 20, 30 wt% of WF as a filler. The obtained results indicate that the mechanical properties of the composite deteriorate when the content of wood flour increases. On the other hand, this filler content has little effect on thermal properties. The authors stated that the PVC/WF composite can be produced by conventional techniques; however, the wood flour content should not exceed 20%. Due to the very high surface energy, nanotubes tend to aggregate and are difficult to disperse in the polymer matrix [80]. Ghasemi et al. [81] presented an analysis of the morphology and mechanical properties of PVC/WF/multiwall carbon nanotubes (MWCNTs) foams. The nanocomposites were prepared in an internal mixer and foamed using a batch process. Nanoparticles were functionalized by sodium hypochlorite solution, and foaming was carried out by using azodicarbonamide as a chemical blowing agent.

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Matuana et al. [82] investigated aminosilane as adhesion promoter, improving significantly the tensile strength of the PVC/wood composites. Authors suggested that treated cellulosic fibers can react with PVC to form chemical bonds. Other treatments (dichlorodiethylsilane, phthalic anhydride and maleated polypropylene) were found to be ineffective, giving strengths similar to those of composites with untreated cellulosic fibers. Xu et al. [83] studied the effect of adding CS to the PVC/WF blend to improved compatibility and thermal stability of material. The thermal degradation temperature of PVC/wood flour composites increased after adding CS.

1.8

Preparation of PVC Membranes, Characterization, Modification, Applications and Mathematical Model

PVC is used in the preparation of membranes, owing to its acceptable characteristics as good mechanical strength, abrasion resistance, chemical stabilization, thermal properties, low cost and corrosion resistance [84, 85]. PVC/polycarbonate (PC) blend ultrafiltration membranes for water treatment were prepared via NIPS method by Behboudi et al. [86]. The polymer solution was prepared from PEG, PVC and PC in NMP. The homogeneous solution was degassed overnight then cast onto a glass plate using an automatic casting knife. Doubé and Walsh [87] studied the behavior of mixtures of PVC with solution chlorinated polyethylene as a function of temperature and investigated the thermally induced phase separation (TIPS) by optical, dynamic mechanical and electron microscope techniques. PVC membrane was prepared by TIPS through using the polymer solution in different weight ratios using tetrahydrofuran (THF) as a solvent. Fang et al. [88] studied blending of PVC/poly(methyl methacrylate-gpolyethylene glycol methacrylate) membranes in water and ethanol immersion baths and observed that the hydrophilicity and antifouling properties of blended membranes were higher than that of neat PVC membrane. Blending of PVC with different percentage of polycarbonate produced high-performance ultrafiltration membrane, where rejection of Bovine serum albumin from synthetic solution was 98.9% using 50% of polycarbonate blending with PVC with high permeate flux. Using a combination of non-solvent induced phase separation (NIPS) and TIPS in PVC membrane preparation can produce ultrafiltration membranes with sponge-like/bi-continuous structures with 60% porosity and rejection of dextran solution more than 90%.

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11

Biobased PVC-Related Blends

A key solution for decreasing the environmental pollution caused by disposal of PVC non-degradable waste is the use of biodegradable polymers, additives and their mixtures. Hachemi et al. [89] realized new bioblends based on PVC and polylactic acid (PLA). These immiscible polymers were compatibilized in situ by using maleic anhydride (MAH), while dicumyl peroxide (DCP) was used as initiator to enhance the blends processability. TGA results showed that the incorporation of PLA in PVC matrix increased the thermal stability of the blends. Phase separation has disappeared in the presence of MAH, microscopic observations revealing uniformly dispersed PLA in the PVC matrix. Different types of PVC nanocomposites containing metals or metal oxides were proposed [90], but efforts were also turned to find natural antibacterial materials that could be easily incorporated in PVC by common techniques [91]. The natural origin of the filler, its particle size and its aspect ratio, as well as its concentration and the homogeneity of its distribution in the polymer matrix are important factors affecting the properties of PVC biocomposites [92]. Compared with synthetic fillers, the natural reinforcements present some advantages such as natural alignment of the carbon–carbon bonds and also its significant strength, stiffness, low density, low cost and biodegradability [93]. PVC bionanocomposites can be also produced by using nanoelements resulted from different renewable resources, e.g., cellulose, starch, chitin [94]. Cellulose nanocrystals characterized by high aspect ratio and a large interface area were used as reinforcing materials in PVC matrix. Blending PVC with biodegradable cellulose derivative is intended also to thermally support the polymer during the molding process, as well as to enhance the biodegradability of PVC waste products. Biodegradable nanocomposites of PVC and nanocellulose whiskers (in content of 0.1%, 0.5%, 1%, 3%, 5%, 8%) isolated from rice straw were prepared by melt-mixing. PVC was used as an additive to crystalline polyhydroxybutyrate valerate (PHBV) to improve PHBV’s mechanical and processing properties, depending on the hydroxyvalerate (HV) content [95]. Compared with PVC materials containing conventional plasticizers, the PVC/polycaprolactone (PCL) blends are tougher, more extensible, with improved softness, and higher resistance to extraction by oil and water [96, 97]. The glass transition temperature of compatible PCL/PVC blends was evaluated by Koleske and Lundberg from the dynamic mechanical tests (DMA) by means of a torsion pendulum [98]. Co-precipitation of cross-linked starch xanthate with PVC latex, co-concentration of a starch and PVC latex, and dry mixing of starch and PVC were used to incorporate three levels of DOP and different amounts of starch in PVC matrix [99]. The influence of starch incorporation into PVC plasticized with di(2-ethylhexyl) adipate (which is susceptible to fungal attack) was assessed by Rosa et al. [100]. Tensile strength at break and elongation at break reduced, while Young’s modulus increased with raising the starch contents of the mixture, indicating that the

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incorporation of starch decreased the plasticized PVC/starch blend flexibility; therefore, a more rigid material resulted due to the formation of new intermolecular interactions probably owing to hydrogen bonds. PVC matrix is blended with natural fillers in order to produce composites with low cost, overall light-weight and good mechanical properties successfully used as construction materials or in the automotive and furniture industries. The natural fillers include wood fiber and lignin [101–103], as well as natural plant fibers such as jute, bamboo, rice straw and sisal [104].

1.10

Conclusions

PVC is widely used since its commercial production in 1930s due to its properties such as good mechanical strength, abrasion resistance, chemical stabilization, thermal properties, low cost and corrosion resistance. Neat PVC or combined with (bio) plasticizers, thermoplastics, rubbers, polysaccharides, minerals, natural fillers or other types of additives are found in various applications, such as building, packaging, automotive, military and aeronautic industries, medicine, ships construction, garden appliances, toys, cards, membranes (e.g., for water treatment). In order to realize performant products containing PVC, different factors should be taken into consideration, such as processing techniques and parameters, the origin of the filler, its particle size and its aspect ratio, as well as its concentration and the homogeneity of its distribution in the polymer matrix. PVC’s biodegradability can be initiated by combining PVC with fillers from renewable sources.

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86. Behboudi A, Jafarzadeh Y, Yegani R (2016) Preparation and characterization of TiO2 embedded PVC ultrafiltration membranes. Chem Eng Res Des 114:96–100 87. Doubé CP, Walsh DJ (1979) Phase diagram of poly(vinyl chloride) and solution chlorinated polyethylene. Polymer 20:1115–1120 88. Fang LF, Zhu BK, Zhu LP, Matsuyama H, Zhao S (2017) Structures and antifouling properties of polyvinyl chloride/poly(methyl methacrylate)-graft-poly(ethylene glycol) blend membranes formed in different coagulation media. J Membr Sci 524:235–244 89. Hachemi R, Belhaneche-bensemra N, Massardier V (2014) Elaboration and characterization of bioblends based on PVC/PLA. J Appl Polym Sci 2014:40045 1–7. https://doi.org/10. 1002/app.40045 90. Machovsky M, Kuritka I, Bazant P, Vesela D, Saha P (2014) Antibacterial performance of ZnO-based fillers with mesoscale structured morphology in model medical PVC composites. Mater Sci Eng C 41:70–77 91. Taurino R, Sciancalepore C, Collini L, Bondi M, Bondioli F (2018) Functionalization of PVC by chitosan addition: compound stability and tensile properties. Compos Part B 149:240–247 92. Saheb D, Jog JP (1999) Natural fiber polymer composites: a review. Polym Adv Technol 18:351–363 93. Dan-asabe B (2018) Thermo-mechanical characterization of banana particulate reinforced PVC composite as piping material. J King Saud Univ Eng Sci 30:296–304 94. Kadry G, Abd El-Hakim AEF (2015) Effect of nanocellulose on the biodegradation, morphology and mechanical properties of polyvinylchloride/nanocellulose nanocomposites. Res J Pharm Biol Chem Sci 6:659–666 95. Choe S, Cha Y-J, Lee H-S, Yoon JS, Choi HJ (1995) Miscibility of poly(3-hydroxybutyrateco -3-hydroxyvalerate) and poly(vinyl chloride) blends. Polymer 36:4977–4982 96. Eastmond GC (2000) Poly(e-caprolactone) blends. Adv Polym Sci 149:59–223 97. Rusu M, Ursu M, Rusu D (2006) Poly(vinyl chloride) and poly(e-caprolactone) blends for medical use. J Thermoplast Compos Mater 19:173–190 98. Koleske JV, Lundberg RD (1969) Lactone polymers. I. Glass transition temperature of poly‐e‐caprolactone by means on compatible polymer mixtures. J Polym Sci Part A-2 Polym Phys 7:795–807 99. Westhoff RP, Otey FH, Mehltretter CL, Russell CR (1974) Starch-filled polyvinyl chloride plastics-preparation and evaluation. Ind Eng Chem Prod Res Dev 13:123–125 100. Rosa DS, Rios AR, Viana HM, Tavares MIB (2015) Characterization of poly(vinyl chloride) compounds containing different levels of starch. J Vinyl Addit Technol 22:396–404 101. Heiden PA (2005) Novel coupling agents for PVC/wood-flour composites. J Vinyl Addit Technol 11:160–165 102. Feldman D, Banu D (1997) Contribution to the study of rigid PVC polyblends with different lignins. J Appl Polym Sci 66:1731–1744 103. Ping QW, Xiao J, Zhao J (2011) The preparation and property of organic solvent lignin and PVC composite materials. Adv Mater Res 236–238:1195–1198 104. Khan RA, Sharmin N, Khan MA, Das AK, Dey K, Saha S, Islam T, Islam R, Nigar F, Sarker B, Debnath KK, Saha M (2011) Comparative studies of mechanical and interfacial properties between jute fiber/PVC and E-Glass fiber/PVC Composites. Polym-Plast Technol Eng 50:153–159

Chapter 2

Polyvinylchloride (PVC): Structure and Properties Relationship Shahzad Maqsood Khan, Nafisa Gull, Rafi Ullah Khan, and Muhammad Taqi Zahid Butt

Abstract Polyvinylchloride (PVC) is one of the widely used synthetic polymers which can be used in many industries like packaging, automobiles, electrical, medical, sports and construction. It can be prepared by different polymerization techniques. Multiple additives like lubricants, fillers, processing aids, pigments, blowing agents, antioxidants, anti-aging agents, UV absorbers, etc., are used to tailor its properties. It can be processed by different techniques to manufacture different products. In this chapter, different methods for the synthesis of PVC along with various polymerization techniques used for its synthesis are discussed. Additionally, different additives, processing techniques, properties, and applications are also reviewed in this text. Keywords PVC

2.1


Properties
Structure
Blends

Introduction

Vinyl chloride (VC) as coined by Regnault in 1835 and its polymer was initially found in 1838 [1]. Baumann described the polymerization of different vinyl halides including VC in the presence of sunlight to get the white powder named as polyvinyl chloride (PVC) in 1872 [2]. After that, technology of polymerization of VC has remarkably progressed mainly in USA and Germany [3]. In early 1930s, commercial production of PVC was first initiated in Germany via emulsion polymerization. The first come-through to surmount the heat stability and processing of PVC introduced in 1932 when Semon discovered the plasticizers for PVC and the use of stabilizers was developed in 1930s [4].

S. M. Khan (&)
N. Gull (&)
R. U. Khan
M. T. Z. Butt Institute of Polymer and Textile Engineering, University of the Punjab, Quaid-e-Azam Campus, Lahore 54590, Pakistan e-mail: [email protected] © Springer Nature Switzerland AG 2022 V. P. M. and R. N. Darie-Nita (eds.), Polyvinylchloride-based Blends, Springer Series on Polymer and Composite Materials, https://doi.org/10.1007/978-3-030-78455-3_2

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In the whole planet, demand for PVC surpasses 35 million tones per annum due to its superior mechanical and physical characteristics, and it is ranked second after polyethylene as volume leader in plastic industry [5, 6]. However, thermal stability and fluid plasticity of PVC are inferior to other commodity plastics like polystyrene and polyethylene [7, 8]. PVC can be processed into a broad diversity of short-life products like packaging materials used in medical devices, beverage packaging bottles, food, textile, and cleansing materials, in long-life commodities like chemical equipments, stationeries, constructional materials, electronic items, roofing sheets, pipes, floor coverings, cable insulations, window frames, etc. [9-14]. Because of some inherited properties of PVC like high performance and low cost, combined with the broad range of items that can be obtained from multiple processing techniques and parameters, PVC became a universal polymer [15]. Currently, there are 50 diverse types of plastics including 60,000 various plastic formulations, and those based on PVC and polyolefins have highest global utilization. As per one estimation, six new plastic materials are sent for assessment and approval to major testing laboratories in USA per week [16].

2.2

Structure

PVC is a vinyl polymer and is analogous to polyethylene, but on every alternative carbon in backbone chain, one of the hydrogen atoms is substituted with chlorine atom [17]. It is a homopolymer with the CAS identification number 002-86-2. Its basic structure is given in Fig. 2.1. Where n, the degree of polymerization, is approximately 300–1700 repeating units. In addition to polymerization, monomer units can add to each other in a number of ways. If we call the methylene (–CH2–) group the tail of the PVC molecule and the carbon chlorine (–HCCl–) portion the head of the molecule, then the following ordering arrangements are possible in the growing polymer chain: i. Head to head ii. Tail to tail iii. Head to tail The predominant order is head to tail.

Fig. 2.1 Chemical structure of PVC

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Fig. 2.2 Polymerization reaction of VC to PVC

Fig. 2.3 Synthesis of PVC from acetylene

2.3

Synthesis

It is synthesized by the free radical polymerization of VC. Polymerization reaction of VC is given in Fig. 2.2. PVC can also be prepared by treating acetylene with hydrochloric acid (HCl) [17]. Its chemical reaction is given below in Fig. 2.3.

2.4

Polymerization Processes

PVC can be processed by radical, emulsion, and suspension polymerization.

2.4.1

Radical Polymerization

Polymerization of VC occurs via free radical addition process, which comprises four elementary reactions: initiation, propagation, chain transfer to monomer, and bimolecular termination steps [18]. The polymerization of VC differs from most other monomers in the sense that PVC is not soluble in its own monomer and in most common solvents. Therefore, in all technical polymerization processes, the prepared PVC separates in very beginning of the reaction in the form of small particles. These often-called primary particles agglomerate into larger granules, depending on the reaction conditions (e.g., polymerization in bulk or in aqueous emulsion or suspension, on concentrations of monomer, initiators, and other regulating agents) and on the further steps during working till the development of technically useful products. Another special quality of VC is its unusual high chain transfer constant, which results in a self-regulation of the molecular weight (MW) [19].

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Fig. 2.4 Head-to-tail arrangement of chain propagation reaction of PVC

According to the ease of homolytic dissociation of the p bond in the monomer, radical polymerization takes place in the presence of suitable initiators. Generally, there are three methods to generate radicals for the polymerization of VC: i. Thermal cleavage of peroxo or azo compounds ii. Redox process iii. Metal alkyls in bonding with oxygen After the initiation step, chain growth started quickly as shown in reaction below in Fig. 2.4. During polymerization, monomer has still another option for reaction with macroradical as shown below in Fig. 2.5. This reaction is head-to-head arrangement, while the above one is head-to-tail sequence. Head to head association is impeded by resonance stabilization and steric hindrance. This irregularity in polymerization capitulates the short chain branching. The final stage of radical polymerization is termination of chain growth commonly by radical transfer reaction to monomer, whereas disproportionation or combination is observed only to small extent. Mostly used procedures for the production of PVC resin are solution, bulk, emulsion, and suspension polymerization. The common feature of the last three processes is that PVC precipitates in liquid monomer at conversion below 1%. The free polymerization of monomer in precipitating medium exhibits an accelerating rate from beginning of reaction up to high conversion. This process is called autoacceleration and common for heterogeneous polymerization of halogenated acrylonitrile and vinyls [20].

2.4.2

Emulsion Polymerization

In emulsion polymerization, water-soluble initiators are used and polymerization occurred in micelles or water. In the system, certain amount of solved monomer also exists. In typical emulsion polymerization of PVC, VC monomer 100 parts,

Fig. 2.5 Head to head arrangement of chain propagation reaction of PVC

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initiator 0.1–0.2 parts, emulsifier 0.1–1 parts, and deionized water 110–140 parts are used. The initiators used for the emulsion polymerization of VC are sodium bisulfate, potassium peroxidisulfate, iron, and copper. Emulsifier is also one of the major ingredients used in emulsion polymerization. Its quantity used is responsible for the latex particle size by finding number of micelles formed. The nature of emulsifier also influences the number of micelles initiated mainly at low concentration. Common emulsifiers are fatty acids ethoxylates, alkyl phenol ethoxylates, fatty acid soaps, sodium salts of alkyl ethoxysulfates, dialkyl sulfosuccinates, alkyl benzene sulfonates, alkyl sulfonates, and alkyl sulfates. The structure of final particles developed by removing the water is important in determination of final properties of plastisol. Therefore, a spray drier is used to isolate the solid product. Dried agglomerates of PVC are obtained by bag filter and cyclone and then milling by pulverizer [21]. PVC obtained by emulsion polymerization is used to develop flexible stuff like artificial leather. PVC powder is mixed with plasticizer to form plastisol which turns into plastigel upon heating. Type, amount, and molecular mass of emulsifier, particle size distribution, and mean particle size of PVC influence the rheology of plastisol [22, 23]. On heating during processing, PVC is dehydrochlorinated as shown in Fig. 2.6 [24].

2.4.3

Suspension Polymerization

Suspension polymerization is the main process used for the development of PVC resins and is used for around 82–85% of US PVC production. One part of VC monomer or comonomer mixture and one or two part of water are charged to an agitated reactor along with initiator and suspending agent, e.g., polyvinyl alcohol. This mixture is reacted at 50–65 °C till 85–90% of the monomer is transformed into resin. Resin–water mixture is also heated under vacuum until unconverted monomer is considerably removed. The resin is then separated from water and dried in flash, rotary, or fluid bed dryers by exposing to hot air. The dried resin is then transferred into silos followed by shipped into fabricating plants in paper bags or in bulk containers. If only VC monomer is reacted, then PVC homopolymer is produced, but if vinyl acetate is mixed with VC, then PVC copolymer is produced. The main advantages of the process of suspension polymerization are its flexibility with regard to polymer composition and resin particle characteristics, its high productivity per unit reactor volume, and the granular nature of its product. Unconverted VC monomer cannot be properly removed due to the production of relatively large resin

Fig. 2.6 Dehydrochlornation of PVC

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particles (50–150 lm). The monomer tends to diffuse slowly from center of the resin particle to the surface, where it is removed by the monomer recovery operation. In the past, in suspension PVC resin, the concentration of residual VC monomer ranged as high as 2000 ppm by weight until advanced methods were developed in response to recognized need for lower residual levels [25].

2.5

Additives

PVC without additives is inflexible and brittle material with inadequate commercial possibilities. This type of PVC degraded severely upon applying pressure and heat, and hydrogen chloride is eliminated and discolored briskly from white to yellow then brown following the black. These changes appeared at processing temperature of around 150 °C [26, 27]. PVC formulations include different types of additives which impart many physical and chemical properties. This versatility has made the PVC a successful commodity thermoplastic from biomedical applications like blood bags and tubing to long-life applications like rainwater goods and window frames. Due to the distinctive polar properties of PVC, broad spectrum of additives can be incorporated to the polymer. The major groups of additives are discussed below:

2.5.1

Heat Stabilizer

Due to the development of some branching during polymerization, commercially produced PVC is intrinsically thermally unstable; therefore, a heat stabilizer is indispensable. Stabilizers are requisite to offer the required stability of the PVC against weathering, light, and heat. Most common stabilizers are organotin compounds and heavy metals as well as organic co-stabilizers, depending upon the required product properties [28].

2.5.2

Plasticizer

Among all additives, frequently used one is plasticizer used in industrial scale processing to perk up some characteristics of PVC like workability and flexibility. The softness and flexibility of PVC depend upon the type and concentration of plasticizer used. They also act as internal lubricants. Dialkyl phthalates are extensively used plasticizers due to their better processing for industrial processing, low cost, and excellent compatibility with PVC. Low MW phthalates provide high mixing and efficiency, even though they are significantly volatile and their diffusion

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and migration into plastisol are too high. Some other phthalates like diethylhexyl phthalate and diisononyl phthalate are frequently used due to their low volatility [29].

2.5.3

Impact Modifier

Pure PVC has comparatively low-impact strength at and below room temperature, and addition of an impact modifier remarkably ameliorates its behavior.

2.5.4

Process Aid

Process aids are primarily added to boost melt flow and fusion characteristics during processing step. Addition levels are usually 1–6 phr with enhancement in surface finish and output. Transparency can also be enhanced during formulation. Chemically, these compounds are high MW alkyl acrylate and methyl methacrylate copolymers.

2.5.5

Lubricant

Lubricants operate classically in two ways: i. Externally to trim down the frictional forces between hot melt surfaces and polymer melt during processing ii. Internally to lessen the friction within polymer matrix and resulted to reduce the effective viscosity

2.5.6

Filler

For most of the PVC applications, fillers are incorporated basically to decrease formulation cost, but some are also employed to improve performance and properties. But acceptable decline in physical characteristics that could result and cost benefits is equally important. At higher concentration of filler, density of the product will increase [30].

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Flame Retardant/Smoke Suppressant

PVC formulation has low flammability because of the existence of chlorine moiety. The inclusion of plasticizer in PVC productions demands the use of smoke-suppressant and flame-retardant additives. These additives are recognized as functional fillers, and their balance is necessary to attain all the ultimate specific requirements.

2.5.8

Pigment

Pigments used for PVC must have good dispersibility, light, and thermally stable and should be compatible with formulation. Inorganic pigments are normally used like titanium dioxide is used to provide opacity, whiteness, and brightness.

2.5.9

Blowing Agent

Solid blowing agents are materials that dissociate to evolve the gases at specific temperature relating to the adequate melt viscosity essential to maintain the structure of foam. There are two major types of blowing agents: (1) sodium bicarbonate, endothermic in nature which absorbs heat to produce carbon dioxide gas and (2) azodicarbonamide, exothermic and dissociate to release nitrogen gas. A variety of grades of these additives are existing to get specific applications and have well-controlled particle size distribution. The azo-based compounds can be particularly tailored to induce an activating agent which initiates the decomposition and increases the total gas released. Blowing agents in granular form cause to improve handling.

2.5.10 Biocide PVP stuff like roofing and flooring material is prone to microbial attack in damping and humid conditions. It is because of the fungi at the outer side of the object as a food source. This can direct to the partial discoloration (black specks or pin color) which can develop a tacky texture where dust particles can accumulate. Unpleasant odors may also be an outcome.

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2.5.11 Viscosity Modifier PVC paste or plastisols must have appropriate viscosity for manufacturing process, handling as well as for storage purpose. This is crucial for thinning under the adequate shear conditions. Paste PVC resin or blends of resin are formulated to persuade a specific rheology profile, but in some cases, incorporation of viscosity modifiers is indispensable. Fumed silica is conventionally used to meet the purpose. Calcium sulfonate gels have also been endorsed to use as viscosity modifier [31].

2.5.12 Antistatic Agent Antistatic agents are incorporated to the PVC formulations to avert the formation of immobile electrical charges, which could direct to a spark or electric shock causing a fire in flammable or dusty area. Dust build-up is also minimized.

2.5.13 Antioxidant Primary antioxidants, like hindered phenols, function as effectual radical scavengers to protect the PVC material during processing and in use (prohibiting photodegradation). Thiosynergists and phosphites are used as secondary anti-oxidizing agents to exsert the effectiveness of the primary anti-oxidizing agents by reducing oxidation intermediates. This can be incorporated in very low concentration at polymerization level and couple with stabilizing package at blending step [32, 33].

2.5.14 Antifogging Agent Antifogging agents are incorporated to food packaging films used for vegetables and meat, specifically which display in the supermarkets [34].

2.5.15 Bonding Agent PVC plastisol, applied on the industrial fabric based on polyamide or polyester fibers, needs the incorporation of chemical bonding agent to promote the interfacial adhesion. Polyisocyanurates based PVC, dispersed in a plasticizer, functions by interacting with polar groups in synthetic fiber to develop strong chemical bonding between PVC and the interface of fabric. These materials are very reactive, and

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PVC plastisol formulations have to consider along with plastisol viscosity build-up. Conventional areas of its use are protective clothing, air-supported coated fabric structures, and truck tarpaulins.

2.5.16 UV Absorber These additives slow the degradation of PVC by UV light [35].

2.6 2.6.1

Processing of PVC Extrusion

Extrusion generates high production rate for volume products of PVC, like wire cable coverings, pipes, and house sidings. Extruded PVC products include downspout systems, gutter, vertical window blinds, and window frames are growing in market. Extruders come in two basic forms: single screw or twin screw. The feedstock determines the requirement of more or less processing time in the extruder. Extruder design is complex but sufficient to melt the PVC pallets or powder without degrading or discoloring the PVC. Some extruders are vented to remove trapped air, and some have forced feed for increased input to the screw. After extrusion, the melt must be shaped and cooled to yield the desired product. Some of the commercial processes for creating particular shapes from extrusion are pipe and tubing, which are pulled through water troughs; sheets, which are cooled and sized on polished rolls; blown film, which is extruded vertically with air entrained to yield a thin film; wire and cable, which spreads molten PVC onto wire pulled through the extruder die into water troughs; PVC coextrusion, which permits multilayer sheets or film of more than one plastic profiles and utilize complex dies to produce various shapes; and fibers, which are drawn down to thread or filament sizes.

2.6.2

Injection Molding

Injection molding allows the designers to create highly complex parts with outstanding structural integrity. Products made by injection molding include appliance components, business machine housings, medical devices, and valves. In the injection molding process, pallets or powder are fed to a heated cylinder. When PVC is molten, it is forced by a screw into a mold. The mold is cooled with

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the molten PVC pressed against the surface. The finished article is ejected with no further processing. Divers shapes can be easily fabricated through this technique, because it is simple, flexible, and versatile. PVC can be molded around nonplastic articles; for example, a screw driver handle can be dipped into plastisol paste and fused. Structural foams can be made with the inclusion of blowing agents. Coinjection molding is a skin and core process with more than one plastic including PVC. The skin and core or sandwich moldings have been used to make high-performance structural foams.

2.6.3

Blow Molding

Blow molding produces bottles in an unlimited variety shapes and sizes. Bottles made from PVC characteristically demonstrate sparkling clarity and high gloss. The resistance of vinyl to fats, oils, and chemicals makes it suitable for items ranging from cooking oil to shampoo to automobile. In extrusion blow molding, a parison (tube-shaped mass of molten PVC) is extruded and encased in a mold. Pressurized air is injected into the parison in the mold to form the bottle. The mold is cooled, and the lower and upper mold flashings, called the tail and moil, are trimmed. In stretch blow molding, the parison is biaxially oriented. This is done by stretching the parison in axial and radial directions. These orientations allow the reduction in the addition of additives and provides additional properties improvements, such as impact and tensile strength, clarity, and barrier resistance. Injection blow molding is also a popular method of fabricating bottles. It has the major advantage of no scrap (i.e., tails and moils as in extrusion blow molding) and can achieve the bottles with uniform wall dimensions. The process involves the manufacture of a preform or parison in a mold. The parison is then placed in blow mold, where air is injected under pressure to form the final bottle shape.

2.6.4

Calendering

Calendering produces films and sheets products of various widths and thicknesses with a limitless range of structures. Major applications of PVC which are obtained by calendering are wall coverings, upholstery fabrics, and both rigid and flexible sheets for consumer products. The calendaring of rigid and flexible PVC comprises about 80% of all calendaring operations in the world.

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Thermoforming

Thermoforming uses heat to shape rigid sheets. The ability of vinyl to mold, sharp the corners, deep cavities and its excellent gloss characteristics have given it a growing share of such product applications e.g. shower and tub units. Other applications, such a blister packaging results from the outstanding clarity of PVC.

2.7 2.7.1

Properties of PVC Physical Properties

One of the most important physical properties of PVC is MW. The MW of PVC is a primary criterion for different commercial grades of PVC. In general, the MW becomes lower as the reaction temperature increases, but chain transfer agents, such as trichloroethylene and 2-mercaptoethanol, can also be used to influence the MW by lowering it at any given polymerization temperature. The MW is a statistical average of polymer molecules with different chain lengths. It is extremely difficult to measure the MW directly, so it is determined in solution form for PVC. The most widely used method for the determination of MW is dilute solution viscosity. Solution viscosity is an indicator of MW of a material and must be related to more direct measurements, such as light scattering, osmometry, or size exclusion chromatography. The measurement of dilute solution viscosity offers an efficient determination of MW data for quality control purposes. It is performed by measuring the flow times of polymer solution in capillary viscometer.

2.7.2

Chemical Properties

Dehydrochlorination: PVC itself is not a thermally stable polymer. To fabricate PVC, heat is required; however, small amount of heat would render uncompounded PVC unusable because of the black color and deteriorated physical properties. The use of heat stabilizers is therefore essential to PVC compounding and fabrication. Heat stabilizers delay or slow the degradation of PVC. Degradation is caused by the dehydrochlorination of the PVC. The mechanism for dehydrochlorination is not completely understood. The popular theory is an “unzipping” of HCl from the polymer to produce colorful polyene structures. A model of the “unzipping” is shown in Fig. 2.7.

Fig. 2.7 Unzipping of PVC

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The most common end groups of PVC chains are allylic and chloroaliphatic. They are resulted from head to head addition as shown in Fig. 2.8. The chlorine atom allylic to the double bond is labile, although the most labile site in the chain is a b-chloroketone that results from copolymerization with oxygen. Once dehydrochlorination has started, new allylic groups are formed and the reaction proceeds to extract HCl in a zipper like fashion. Internal allylic sites are more reactive than those at the end of the chain. PVC can undergo many chemical reactions which include dehydrochlorination, hydrogenation, chlorination, and radiation crosslinking. Some of the treatments are useful to elucidate the chemical structure of the PVC polymer chain. The only commercially significant chemical treatment is postchlorination, which yields the product chlorinated PVC (CPVC). PVC contains 56.7% chlorine while CPVC contains up to 73% Cl after treatment. Postchlorination gives the resin an increased heat distortion temperature, and the resin is useful in such applications as initiator hot water lines and certain drain, waste, and vent applications.

2.7.3

Electrical and Optical Properties

Electrical properties of PVC are of remarkable importance due to their extensive electrical applications. It is used as one of the easily molded insulators. Electrical properties of PVC depend not only on the structural features and chemical composition but also on the degree of molecular order. The dielectric properties of PVC provide the description of hopping process and rotation of electrons involved in

Fig. 2.8 PVC structure with allylic and chloroaliphatic end groups

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PVC and explicate the dispersion phenomenon linked with molecular configuration and its ordering as it influences the conductivity of material [36]. PVC is used as an insulating material in wire and cable and in many electrical appliances. To determine the effect of formulation variables on this insulating property, the following tests are used: (1) resin conductivity (D1755); (2) volume resistivity (D257); and (3) insulation resistance (e.g., as performed by the Underwriters’ Laboratory or the National Electrical Manufacturers Association). Optical properties are of great importance due to imparting better polarization, interface, antireflection, and reflection properties [37]. Optical absorption studies are crucial to render the details of type of optical transitions, localized states, and electronic band structures which makes these materials striking for chemical sensors for the detection of ionic species and display panels [38-41]. The shape and value of the mobility gap in PVC depend on proportion conditions like degree of impurity, substrate temperature, and defect of the material. Any disparity in these parameters leads to a shift in the absorption edge toward lower or higher energy [21].

2.7.4

Thermal Properties and Flammability

The glass transition temperature Tg is the most considerable thermal parameter of PVC. It is the temperature at which PVC changes from a hard or glassy state to a soft, rubbery state [42]. PVC exhibits characteristic thermal transitions as it is systematically heated in a differential scanning calorimeter (DSC). PVC is glassy at room temperature, and when heated at or near its Tg, its modulus and heat capacity change abruptly. Tg is directly related to MW; additives can affect Tg as well. PVC does not have a precise melting point. A softening point is sometimes quoted, but it is imprecise and often misleading. The compounding of plasticizer with PVC changes the Tg. Small amount (10–15%) of di-2-ethylhexylphthalate and dioctyl phthalate (DOP) plasticizers, actually causes the Tg to increase because there is an apparent ordering of the polymer chains and subsequent increase in crystallinity. This maximum in tensile strength and modulus is called the antiplasticizer effect. At high DOP level, the anticipated decrease in Tg occurs. In addition to DSC, other thermal techniques can measure specific heat, thermal conductivity, expansion, and diffusivity. The flammability of PVC is a complex phenomenon and normally comprises of balancing physical properties, thermal stability, and flame retardancy [43]. PVC has superior innate flame-retarding properties owing to its chlorine content. Its flammability rating in UL94 is V-0 level, even without inclusion of fire retardants. For instance, the ignition temperature of PVC is 455 °C and cannot easily ignite with less risk of fire incidents [21]. But as other plastics, PVC is still classified as ordinary combustibles. According to the National Fire Protection Association (NFPA), the lack of thermal stability of plastics at high temperature has abolished the use of plastics in applications where high fire retardance is required. The flammability of PVC products should be categorized for those close to people’s

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daily lives like floor and wall panel used inside the rooms. The details of PVC flammability could be traced back to early 1980s [44, 45]. The flammability behavior of PVC imparts a significant part in its assortment for many applications. Its comparatively high chlorine content (56.8%) composes it more resistant to burning and ignition than most organic polymers. In the case of flexible PVC, the plasticizers that impart flexibility detract from its retardance to fire. To attain the specific properties like heat release, oxygen index, extent of burning in cable tests, smoke evolution, smoke-suppressant, and flame-retardant additives are required to meet stringent flammability specifications cost effectively [46].

2.7.5

Mechanical Properties

Mechanical properties of PVC are given in Table 2.1.

2.7.6

Morphology

The morphology or shape of PVC particles is important for product performance characteristics. If the gross particles are isotropic or round and smooth, gravity feed into extruders is more rapid and desirable. If the microstructure of PVC is articulated, plasticizer absorptivity and fusion characteristics are enhanced. If the dispersion resin aggregates are friable into particular particle size distributions, then plastisol viscosities can be very low. Porosity is critical to residual vinyl chloride monomer (RVCM) removal and to resin properties and is influenced by.

Table 2.1 Mechanical properties of PVC according to CES edupak © [47]

Mechanical properties Minimum value Young modulus Bulk modulus Shear modulus Compressive strength Poisson’s ratio Maximum value Young modulus Bulk modulus Shear modulus Compressive strength Poisson’s ratio

PVC 2.140 4.700 0.766 42.500 0.383

GPa GPa GPa MPa

4.140 4.900 1.490 89.600 0.407

GPa GPa GPa MPa

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Polymerization temperature Conversion Chemical type and concentration of suspending agent Use of secondary suspending agents Use of secondary surfactants Reaction parameters such as agitation and water–monomer ratio

Chemical parameters are also significant to the control of particle morphology and porosity in particular. As more primary suspending agent is used in polymerization, particle size decreases. Some suspending agents reduce interfacial tension more than others and are therefore more efficient in controlling particle size. Greater efficiency and porosity control are generally gained when secondary suspending agents or surfactants are used in addition to the primary dispersants. With more efficient surfactants, particle size generally decreases, bulk density increases, and porosity increases. The model for this effect is the placement of chemical wicks or areas of transport for RVCM during stripping process or for plasticizer swell the particles during fabrication.

2.7.7

Crystal Structure and Crystallization Behavior

PVC is highly amorphous, with very low degrees of crystallinity from some syndiotactic polymer sequence as formed in typical commercial process. If the order is forced by polymerization conditions, such as extremely low reaction temperatures (−50 to −100 °C), then a crystalline PVC can be synthesized. When there is no order or random order of the polymer chain, it is called atactic, and PVC generally fits this category. Crystallinity is linked with syndiotactic arrangement of PVC. Though syndiotactic arrangements acquired from radical polymerization are normally short, there are strong attractive forces between PVC chains linked with C–Cl dipoles that are responsible to provoke crystallinity [48]. The melting point of completely syndiotactic PVC reported in the literature is about 400 °C [49], but such perfectly syndiotactic polymer has not been synthesized yet. The melting point of PVC synthesized by free radical polymerization is ranged between 102–210 °C due to small size and blemishes in ordered structure [50]. Crystallinity of the PVC also depends upon gelation mechanism [51]. Mostly commercial PVC has 7–20% crystallinity [52, 53]. Crystallinity of PVC improved when polymerization was taken place at lower temperature [54]. The crystallites behave as physical crosslinks in commercial products. The unit cell dimensions for syndiotactic PVC are found to be orthorhombic unit cell with a, b, and c dimensions of 1.06, 0.54, and 0.51 nm, respectively [55].

2 Polyvinylchloride (PVC): Structure and Properties Relationship

2.7.8

35

Weathering and Radiation Resistance

PVC deteriorates when exposed to natural weather and becomes increasingly brittle and colored and causes steadfast decline in mechanical properties like impact resistance, elasticity, and tensile strength. Due to its broad outdoor applications, PVC has to be shielded against photodegradation [56]. The major parameters effecting the degradation of PVC items including humidity, oxygen, mechanical stress, light, ionizing radiations, and aggressive media are accelerated by raising temperature. The degradation of PVC directs to change in fundamental properties as a result of simultaneous physical and chemical processes causing changes in structure and chemical composition [57]. Dehydrochlorination can be used to follow changes in the stability of rigid PVC during outdoor exposure [58]. The weathering of PVC is greatly affected by its thermal history (synthesis and processing). PVC compounds that have been mixed for long periods or mixed and processed at high temperatures show poor outdoor performance. The photo-oxidation of PVC can be illustrated by the following sequence [59, 60]. i. Multistep photochemical excitation develops photolytic formation of polyene chains with increasing conjugation lengths. Excitation of chromophoric imperfections having structure of a-chlorinated dienes initiates this photolysis. These reactions conduce to significant discoloration and resulted polyenic arrangements which are promptly photo-oxidized in the presence of molecular oxygen. In this process, photobleaching phenomenon is noticed to be taken place. ii. Photochemical oxidation that can be started by Cl* formed along with the polyenic sequences and that resulted in the formation of following major products: acid chlorides, b-chlorocarboxylic acid, and a,ά-dichloroketones. iii. Crosslinking of PVC by rejoining of chain macroradicals [61]. Exposure of plasticized PVC to ionizing radiation, e.g., gamma rays or electron beam, causes changes in physicochemical and biological properties of material as described in the literature [62, 63]. The distinct discoloration of PVC occurs at a typical sterilization dose of 25 kGy; the material tends to darken or to turn yellow. This process is autocatalytic and continues after sterilization. During irradiation of PVC, the conjugated double bonds as well as the significant quantities of hydrochloric acid are produced due to the oxidation of PVC resins. The polyene structure is the reason of discoloration of PVC compositions. Moreover, the crosslinking and chain scissioning reactions that lead to change in MW and mechanical properties are possible [64]. Plasticized PVC requires numerous additives that can significantly affect the material behavior during irradiation. All these ingredients, e.g., plasticizer, stabilizer, and lubricant can be decomposed and may contaminate medical formulation with decreasing the biocompatibility of material [65]. Several different approaches have been adopted to improve the radiation resistance of PVC compositions. A key idea is the creation of protective effect using compounds which act as an energy

36

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transfer agent without changing polymer properties such as organotin mercaptoacid esters, aromatic compounds with poly-membered rings, some fillers, gadolinium, and lanthanum compounds. Unfortunately, the above-mentioned compounds are toxic and cannot be used in medical formulations [66]. Unluckily, exposure of gamma radiations on flexible PVC has negative impact on its appearance. After sterilization, the PVC products turn to darken yellow but viscosity and physical properties remain unchanged. Compound darkening is an autocatalytic phenomenon, and it persists after sterilization during the shelf life between sterilization and item use. The darkening of the product is ascribed to the development of conjugated double bonds due to the oxidation reaction of PVC resin [67]. The extent of darkening of PVC depends upon the formulation and shelf life of product. Conventional inexpensive flexible PVC products undergo extreme darkening after gamma sterilization. To reduce this effect, proper compound formulation is crucial. Choice of antioxidant, lubricant, stabilizer, and resin influences the color stability after exposure of gamma radiations [68].

2.8

Suppliers

Item-wise/supplier summary report. Supplier

Origin

Quantity (kgs)

Total value

2833.1900 PVC resin post-industrial recycled PIR in powder Zhengzhou Aceto Chemicals China 27,000.00 13,500.00/– Total quantity 27,000.00 13,500.00/– 27.00 Tons 3206.4910 11 PVC resin color. approximate net weight 35 kgs Shenzhen City victory Prosper China 35.00 108.50/– Total quantity 35.00 108.50 0.03 Tons 3901.2000 PVC resin HD polyethylene HE3460 2X40 total 4X40 STC 3952 bags 101,171 kgs empty Borouge PTE Ltd. P.O. Box 6951 ABU United Arab 51,080.00 127,700.00 Dibaj Al Khaleej Plastic Ind LLC United Arab 27,000.00 54,000.00 Total quantity 78,080.00 181,700 78.08 Ton 3902.1000 PVC resin polypropylene RA140E 2X40 50,091 kgs Borouge PTE Ltd. P.O. Box 6951 ABU United Arab 50,091.00 125,227.50 Total quantity 50,091.00 125,227.50 50.09 Ton (continued)

2 Polyvinylchloride (PVC): Structure and Properties Relationship

37

(continued) Supplier 3902.9000 4175 PVC resin Federal Express

Origin United Arab Total quantity

Quantity (kgs)

Total value

1.00 10.00 1.00 10.00 0.00 Ton 3904.1010 PVC resin Akropan 1,108,414 FX 5X40 STC 100 Paleet 115,240 kgs empty container is Akdeniz Kimyasal Urunler Paz. IC VE Turkey 135,788.00 339,470.00 Beneficiary Norway 43,200.00 42,768.00 CGPC Polymer Taiwan/Sep 50,000.00 48,000.00 CGPC Polymer Taiwan/Sep 25,000.00 24,000.00 Dibaj Al Khaleej Plastic IND LLC United Arab 42,840.00 44,982.00 Evergreen Ocean Hk Limited China 14.00 42.00 Hanwha Chemical Corporation Korea Republic 31,200.00 41,808.00 Inner Mongolia Wuhai China 17,000.00 16,150.00 Inovyn Belgium SA France 618,750.00 638,055.00 Inovyn Norge AS Norway 86,400.00 88,128.00 KPL International Ltd. France 122,375.00 127,270.00 LG Chem Ltd. Korea Republic 44,800.00 56,448.00 LG Chem Ltd. Korea Republic 33,600.00 43,008.00 LG Chem Ltd. Korea Republic 24,000.00 30,720.00 Multi Trade Limited FZC Saudi Arabia 50,112.00 125,280.00 Nordic Industries FZE United Arab 40,500.00 101,250.00 PWSC International FZC China 81,918.00 122,877.00 Ramtech Overseas Inc. United States 126,980.00 133,329.00 SCG Plastics Co. Ltd. Thailand 72,000.00 68,400.00 Unitcargo Container Line Inc. 4544 United States 18,140.00 19,228.40 Vinythai Public Company Limited Thailand 1502,000.00 1635,660.00 Vinythai Public Company Limited, 2 Thailand 12,500.00 13,875.00 Vinythai Public Company Limited, 2 Thailand 12,500.00 14,000.00 Vinythai Public Company Limited Thailand 2821,000.00 3093,790.00 Vinythai Public Company Ltd. Thailand 66,000.00 57,420.00 Total quantity 6,078,617.00 6,925,958.40 6,078.61 Ton 3904.1090 PVC resin suspension gradesg660 for shoe industry Thailand 108,000.00 98,280.00 CGPC Polymer Corp. Kaohsiung Taiwan/Sep 25,000.00 23,250.00 CGPC Polymer Corporation Taiwan/Sep 732,000.00 686,720.00 CGPC Polymer Corporation Taiwan/Sep 75.00 66.00 CGPC Polymer Corporation Taiwan/Sep 500,000.00 466,000.00 CGPC Polymer Taiwan/Sep 300,000.00 277,000.00 CGPC Polymer Corporation Taiwan/Sep 100,000.00 90,000.00 (continued)

38

S. M. Khan et al.

(continued) Supplier

Origin

Quantity (kgs)

Total value

Elite Piping Manufacture Co Ltd. Federa Express Federa Express Formosa Plastics Corporation Formosa Plastics Corporation GO Green FZC H. SAGA International Co H. SAGA International Co. Ltd. H. SAGA International Co. Ltd. H. SAGA International Co. Ltd. Haining Oumeijia Plastic Steel Hanwha Chemical (Ningbo) Co. Ltd. Hanwha Chemical Corporation Hanwha Corporation Hanwha Corporation Hanwha Corporation Hanwha Corporation Hanwha Corporation, 22nd floor Hanwha Corporation, 22nd floor Hubei Yihua Chemical Industry Co Hubei Yihua Chemical Industry ICC Handels AG Inner Mongolia Wuhai Chemical Inner Mongolia Wuhai Chemical Inner Mongolia Wuhai Chemical Inovyn Europe Limited Succursale Itochu Plastics Pte. Ltd. Itochu Plastics Pte. Ltd. Just Right Middle East FZCO KPIC Corporation Kyoung Sin Co. Ltd. L.S. & Dan International Ltd. Mexichem Resinas Vinilicas S.A DE Mexichem Resinas Vinilicas S.A DE Mitsui & Co. Ltd. Mitsui and Co. Ltd. 1-3 Marunouchi MTS Logistics Inc. 5 West 37th MTS Logistics Inc., USA MTS Logistics Inc. MTS Logistics Inc. 5 West 37th

China United Arab United Arab Taiwan/Sep Taiwan/Sep Polano Taiwan/Sep Taiwan/Sep Taiwan/Sep Taiwan/Sep China China Korea Republic China China China China China China China China Europien Union China China China Belgium Taiwan/Sep Taiwan/Sep China United States Korea Republic United Kingdom Mexico Mexico Japan Japan United States United States United States United States

50.00 1.00 1.00 352,000.00 112,500.00 1,250.00 100,000.00 200,000.00 325,000.00 25,000.00 250.00 50,000.00 22,900.00 291,500.00 136,000.00 353,000.00 50,000.00 50,000.00 68,000.00 78,000.00 78,000.00 148,500.00 1335,500.00 208,000.00 1586,000.00 74,250.00 108,000.00 180,000.00 2,000.00 303,875.00 115,530.00 21,660.00 178,500.00 76,500.00 88,600.00 17,000.00 93,500.00 53,000.00 931,000.00 110.00

460.00 10.00 40.00 329,780.00 104,625.00 1,250.00 94,000.00 190,000.00 295,625.00 22,250.00 250.00 46,500.00 21,526.00 265,265.00 129,200.00 333,350.00 48,000.00 48,500.00 64,600.00 74,100.00 73,580.00 145,530.00 1160,112.50 187,200.00 1414,140.00 72,022.00 99,360.00 169,200.00 1,900.00 293,239.00 51,988.50 12,996.00 162,180.00 65,790.00 84,002.00 14,620.00 86,020.00 48,760.00 838,948.75 94,600.00 (continued)

2 Polyvinylchloride (PVC): Structure and Properties Relationship

39

(continued) Supplier

Origin

Quantity (kgs)

Total value

MTS Logistics Inc. 5 on behalf of Multi Trade Limited Fzc Polymer Chemicals Limited Polymer Commodities Limited Polyplast PTE Ltd. Powell International Trading Pt Asahimas Chemical Pt Asahimas Chemical Pt. Sulfindo Adiusaha PT. TPC Indo Plastic PT. TPC Indo Plastic And Chemicals PT. TPC Indo Plastic and Chemicals PT. TPC Indo Plastic Chemicals Qingdao Haijing Chemical Qingdao Shida Chemical Co. Ltd. Qingdao Shida Chemical Co. Ltd. Qingdao Shida Chemical Co. Ltd. Qingdao Shida Chemical Co. Ltd. Qingdao Shida Chemical Co. Ltd. Saudi Basic Industries Saudi Basic Industries SCG Plastics Co Ltd. SCG Plastics Co Ltd. SCG Plastics Co Ltd. SCG Plastics Co Ltd. SCG Plastics Co Ltd. SCG Plastics Co Ltd. SCG Plastics Co Ltd. Shin ETSU Chemical Co Ltd. Tianjin Dagu Chemical Co. Ltd. Tianjin LG Bohai Chemical Tianjin LG Bohai Chemical Tianjin LG Bohai Chemical Co Ltd. Tianjin LG Bohai Chemical Co Ltd. Tianjin LG Bohai Chemical Co Ltd. Tianjin LG Bohai Chemical Co Ltd. Tianjin LG Bohai Chemical Co Ltd. Tianjin LG Bohai Chemical Co Ltd. Tianjin LG Bohai Chemical Co Ltd. Tianjin LG Bohai Chemical Co Ltd.

United States United Arabs China China Mexico Taiwan/Sep Indonesia Indonesia Indonesia Indonesia Indonesia Indonesia Indonesia China China China China China China Saudi Arabia Saudi Arabia Thailand Thailand Thailand Thailand Thailand Thailand Thailand Japan China China China China China China China China China China China

241,500.00 50,056.00 68,000.00 26,000.00 306,000.00 525,000.00 16,000.00 168,000.00 122,500.00 36,000.00 508,000.00 108,000.00 17,500.00 104,000.00 106,000.00 26,500.00 1086,500.00 106,000.00 106,000.00 99,000.00 24,750.00 54,000.00 54,000.00 162,000.00 108,000.00 396,000.00 144,000.00 984,500.00 75.00 237,500.00 52,000.00 52,000.00 68,000.00 102,000.00 52,000.00 52,000.00 104,000.00 312,000.00 104,000.00 312,000.00

225,310.00 48,323.50 170,000.00 65,000.00 285,600.00 492,375.00 14,400.00 161,520.00 122,150.00 32,400.00 489,220.00 98,280.00 16,625.00 99,320.00 100,700.00 24,645.00 999,315.00 100,700.00 100,700.00 90,090.00 22,522.00 51,300.00 51,120.00 162,072.00 102,636.00 367,515.00 140,580.00 925,059.60 67.50 220,315.00 49,400.00 48,360.00 170,000.00 255,000.00 48,360.00 51,480.00 94,640.00 292,240.00 94,640.00 292,240.00 (continued)

40

S. M. Khan et al.

(continued) Supplier

Origin

Tianjin LG Bohai Chemical Company Tianjin LG Bohai Chemical Company Tianjin LG Bohai Chemical Company Unitcargo Container Line Inc. Unitcargo Container Line Inc. 4544 Unitcargo Container Line Inc. Unitcargo Container Line Inc. C/O Unitcargo Container Line Inc. C/O Vinythai Public Company Limited Vinythai Public Company Limited Xinjian Tianye Group Foreign Xinjiang Tianye Foreign Trade Xinjian Tianye Group Foreign Xinjian Tianye Group Foreign Xinjian Tianye Group Foreign Xinjian Tianye Group Foreign Xinjian Tianye Group Foreign Xinjian Tianye Group Foreign Yiwu Juyanghong Trading Zed’S Plastic Recycling

China China China United States United States United States United States United States Thailand Thailand China China China China China China China China China United Kingdom Total quantity

Quantity (kgs)

Total value

104,000.00 98,800.00 426,500.00 400,395.00 1352,000.00 1267,500.00 23,375.00 22,089.37 23,375.00 21,972.50 46,750.00 43,945.00 387,750.00 357,142.50 116,875.00 93,500.00 594,000.00 559,680.00 99,000.00 98,010.00 28,000.00 19,600.00 77,250.00 73,387.50 52,000.00 46,800.00 354,500.00 318,415.00 47,000.00 32,900.00 51,500.00 48,925.00 77,250.00 73,387.50 51,500.00 43,260.00 2,125.00 2,125.00 19,800.00 13,464.00 20,299,983.00 19,211,476.10 20,299.98 Ton 3904.2100 PVC resin and compound extrusions compound Dyyblend PVC 1309 Rehau AG + Co. Germany 30,504.00 55,673.50 Rehau AG + Co. Germany 15,975.00 29,731.07 Rehau AG + Co. Germany 14,529.00 23,246.40 Rehau AG + Co. Germany 16,300.00 26,080.00 Total quantity 77,308.00 134,730.97 77.30 Ton 3904.9000 7891 PVC resin 200 GRM Federal Express United Arab 1.00 10.00 Total quantity 1.00 10.00 0.00 Ton 3906.9090 808,484,707,684 PVC resin sample 3 kg Federal Express United Arab 3.00 60.00 Total quantity 1.00 60.00 0.00 Ton 3907.3000 7118 PVC resin Federal Express United Arab 1.00 10.00 S F Express China Limited Singapore 2.00 52.00 TNT Express W W United Arab 19.00 502.00 (continued)

2 Polyvinylchloride (PVC): Structure and Properties Relationship

41

(continued) Supplier

Origin

Quantity (kgs)

Total value

TNT Express World Wide TNT Express World Wide

United Arab United Arab Total quantity

1.00 3.00 26.00 0.02 Ton

38.00 197.00 799.00

1.00 1,267.90 522.20 295.10 129.00 61.90 2,277.10

10.00 6,405.19 2,954.63 1,570.18 676.03 304.87 11,9920.92

0.00 57.00 57.00 0.05 Ton

0.00 473.23 473.23

United Arab Total quantity

0.40 0.40 0.00 Ton

3.82 3.82

United Arab Total quantity

6.00 6.00 0.00 Ton

53.03 53.03

1.00 1.00 3.00 5.00 0.00

30.00 65.00 189.00 284.00

1.00 1.00 0.00 Ton

5.00 5.00

32.00 32.00 0.03 Ton

170.56 170.56

3907.9900 9,118,802,405 PVC resin DHL Avation UK Ltd. DHL Avation UK Ltd. DHL Express Intl (TH) Ltd. DHL Express Intl (TH) Ltd. DHL Worldwide Express Shah Agencies

Belgium United Kingdom Thailand Thailand United Arab Thailand Total quantity 3909.1090 811,602,730,103 PVC resin sample Federal Express United Arab United Parcel Services United Arab Total quantity 3909.3000 807,093,241,477 PVC resin Federal Express

3909.4000 418,072,756,747 PVC resin Federal Express

3909.5000 4,705,756,532 PVC resin 5 kg DHL Express International Th Ltd. Thailand DHL World Wide United Arab Shah Agencies Thailand Total quantity 3920.4990 9975 … PVC resin sample … 01 PC Sky Networldwide Express Hong Kong Total quantity 3920.9400 2,144,524,071 PVC resin DHL Express Intl (TH) Ltd.

Thailand Total quantity

(continued)

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S. M. Khan et al.

(continued) Supplier 3921.9090 6,738,530,260 PVC resin DHL Aviation UK Ltd.

Origin

Quantity (kgs)

Total value

United Kingdom Total quantity

78.00 78.00 0.07 Ton

371.28 371.28

16.00 5.00 2.00 1.00 1.00 50.00 21.00 1.00 1.00 3.00 122.00 9.00 29.00 1.00 1.00 13.00 2.00 278.00 0.27 Ton

126.49 54.04 6.65 15.00 30.00 239.00 443.00 5.00 154.00 60.00 1,969.26 115.00 214.94 10.00 5.00 595.00 31.69 4,074.07

3926.9099 715,890,532,869 PVC resin 500 g Allied Business Corporation United Arab Aramex Emirates LLC United Arab Aramex Intl Courier United Arab DHL Avation UK Ltd. United Arab DHL Aviation N.V United Arab DHL Aviation UK Ltd. United Kingdom DHL Express International TH Ltd. United Kingdom DHL Fra Intl Gmbh Germany DHL World Wide United Arab DHL Worldwide Express United Kingdom Federal Express United Arab Federal Express United Arab Shah Agencies United Kingdom TCS Express United Arab TCS Express WW United Arab UPS Air Couriers of America United Arab UPS Air Couriers of America United Arab Total quantity

2.9 2.9.1

Applications Construction

In construction industry, PVC is used in many fields including cables ducting and conduits, guttering, potable and gravity pipes, window frames and doors, roller shutters, sheets and panels, reservoir linings, wall covering, flooring, sports stadium seats, etc.

2 Polyvinylchloride (PVC): Structure and Properties Relationship

2.9.2

43

Medical

In medical field, infusion kits, tubing, plasma bags, blood bags, pharmaceutical blisters, etc., are prepared from PVC.

2.9.3

Electrical

Electrical appliances, component housings, cellular phones, phone systems, electrical cords, power tools, computers, keyboards, etc., are made up of PVC in electronics industry.

2.9.4

Automobiles

In automobile sector, wire harness systems, (cable sheaths grommets, dashboard skins, and window encapsulation), coated fabrics (seat coatings door panels), interior trims (gearbox lever parts carpets and sun visors handbrake), and sealant (underbody insulation) are developed from PVC.

2.9.5

Packaging

Bottle caps, non-food packaging, e.g., detergent containers, trays cosmetics and food packaging, like thermoformed cups are prepared from PVC in this modern era.

2.9.6

Cards

Identity cards, smart cards, credit cards, and telephone cards are made up of PVC nowadays.

2.9.7

Leisure and Sports

Ships construction, life rafts, garden hoses, swimming rings, footballs, and toys are also made up of PVC.

44

2.9.8

S. M. Khan et al.

Office

PVC is used to prepare computer keyboards, computer cases, office supplies such as folders, ring binders, rulers, and binding application.

2.9.9

Clothing

Rubber boots, shoe soles, imitation leather, life vests, and raincoats are prepared from PVC in clothing section [69].

2.10

Future and Environmental Impact

PVC become the polymer having most environmental risks like, elimination of hydrogen chloride during combustion and processing, treatment of very toxic monomer and the attack of antichlorine activists due to the public reservation against chlorine chemistry. PVC has high chlorine content as it devours a large fraction (approximately 30%) of the total chlorine production as a by-product of caustic soda. But taking into account all the progress, there are several future demands for long-term development and research by collaboration of the PVC industry, e.g., for the production of non toxic plasticizer, metal free and non toxic stabilizer, to overcome the peril of substitution of PVC by other polymers, e.g., by thermoplastic elastomers. The advancement of new PVC products with better properties should also be an objective for PVC industry, i.e., via blending or grafting to develop a new engineering plastic from commodity polymer. Another demand is sound knowledge of the community about the manifestation of the product recyclability of product and the achievement in dropping ecological effluence. It is also obligatory to enhance efforts for healthier communication with public in construction industry, which is, for instance successful in Germany, where about 1.5 million tons utilization of PVC takes place, about 2/3 was consumed in building sector, which was approximately twice the amount of styrene and polyolefins polymers added together. If all the intrinsic properties of this commodity polymer were used, further development of this polymer can be anticipated. In this context, one should remember what the memorable Herman Mark said fifteen years back in the preface of Encyclopedia of PVC: “old stories never die—they just fade away. Old plastics never die—they hang on and stay” [70].

2 Polyvinylchloride (PVC): Structure and Properties Relationship

2.11

45

Conclusions

In this chapter, detailed description of PVC including brief history, chemical structure, laboratory scale synthesis and polymerization processes like radical, emulsion, and bulk polymerizations are discussed in detail. PVC along with the addition of different additives is employed to improve its properties for different applications. PVC can be processed in different modes to develop diversified products. Different properties of PVC like physical, chemical, electrical, optical, thermal, mechanical, and morphological behavior are also studied. Consumption of PVC in different sectors like electrical, transport, medical, clothing, etc., is also discussed. Suppliers of PVC from different countries are listed here in this chapter. Furthermore, the future outlook and environmental impact of PVC is elaborated for its use in further development.

References 1. Regnault V (1835) About the composition of the chlorinated hydrocarbon (oil of the oil-forming gas). Eur J Org Chem 14:22–38 2. Baumann E (1872) Uber einige vinylverbindungen. Liebigs Ann Pharm 163:308–322 3. Mark HF (1989) Encyclopedia of polymer science and engineering. Wiley, New York 4. Morawetz H (1982) History of polymer science and technology. Marcel Dekker, New York 5. Braun D (2002) Recycling of PVC. Prog Polym Sci 27:2171–2195 6. Nakamura S, Nakajima K, Yoshizawa Y, Matsubae-Yokoyama K, Nagasaka T (2009) Analyzing polyvinyl chloride in Japan with the waste inputeoutput material flow analysis model. J Ind Ecol 13:706–717 7. Endo K (2002) Synthesis and structure of poly(vinyl chloride). Prog Polym Sci 7:2021–2054 8. Finch CA (1989) Encyclopedia of polymer science and engineering. Wiley, New York 9. Garcia D, Balart R, Crespo JE, Lopez J (2006) Mechanical properties of recycled pvc blends with styrenic polymers. J Appl Polym Sci 101:2464–2471 10. Braun D (2001) PVC-Origin, growth, and future. J Vinyl Addit Technol 7:168–176 11. Wenguang M, Mantia FP, La. (1996) Processing and mechanical properties of recycled PVC and of homopolymer blends with virgin PVC. J Appl Polym Sci 59:759–767 12. Sadat-Shojai M, Bakhshandeh G-R (2011) Recycling of PVC wastes. Polym Degrad Stab 6:404–415 13. Burat F, Güney A, Kangal MO (2009) Selective separation of virgin and post consumer polymers (PET and PVC) by flotation method. Waste Manage 29:1807–1813 14. Matuschek G, Milanov N, Kettrup A (2000) Thermoanalytical investigations for the recycling of PVC. Thermochim Acta 361:77–84 15. Yarahmadi N, Jakubowicz I, Martinsson L (2003) PVC floorings as post consumer products for mechanical recycling and energy recovery. Polym Degrad Stab 79:439–448 16. Limbachiya RR, Limbachiya VJ, Mehsana RRL (2014) A review of experimental investigation of twin screw extruder (TSE) machine for polyvinyl chloride (PVC) polymer material. Int J Eng Dev Res 2:1631–1634 17. Tahira BE, Khan MI, Saeed R, Akhwan S (2014) A review: thermal degradation and stabilization of poly(vinyl chloride). Int J Res 1:732–750

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18. Krallis A, Kotoulas C, Papadopoulos S, Kiparissides C, Bousquet J, Bonardi C (2004) A comprehensive kinetic model for the free-radical polymerization of vinyl chloride in the presence of monofunctional and bifunctional initiators. Ind Eng Chem Res 43:6382–6399 19. Braun D (2005) Controlled free-radical polymerization of vinyl chloride. J Vinyl Addit Technol 11:86–90 20. Kricheldorf HR, Nuyken O, Swift G (1999) Handbook of polymer synthesis. CRC Press 21. Yousif E, Abdallh M, Hashim H, Salih N, Salimon J, Abdullah BM, Win Y-F (2013) Optical properties of pure and modified poly(vinyl chloride). Int J Ind Chem 4:1–8 22. Borroso EG, Duarte FM, Couto M, Maia JM (2008) A rheological study of aging of emulsion and microsuspension based PVC plastisols. J Appl Polym Sci 109:664–673 23. Rasteiro MG, Tomás A, Ferreira L, Figuredo S (2009) PVC paste rheology: study of process dependencies. J Appl Polym Sci 112:2809–2821 24. Savrık SA, Balköse D, Ulutan S, Ülkü S (2010) Characterization of poly(vinyl chloride) powder produced by emulsion polymerization. J Thermal Anal Calorimtry 101:801–806 25. Wheeler RN (1981) PoIy(vinyl chloride) processes and products. Environ Health Perspect 41:123–128 26. Unar IN, Soomro SA, Aziz S (2010) Effect of various additives on the physical properties of polyvinylchloride resin. Pak J Anal Environ Chem 11:44–50 27. Elgozali A, Hassan M (2008) Effect of additives on the mechanical properties of polyvinylchloride. J Sci Technol 9:1–12 28. Mersiowsky I (2002) Long-term fate of PVC products and their additives in landfills. Prog Polym Sci 27:2227–2277 29. Jimenez A, Lopez J, Iannoni A, Kenny JM (2001) Formulation and mechanical characterization of PVC plastisols based on low-toxicity additives. J Appl Polym Sci 81:1881–1890 30. Yousif E, Hasan A (2015) Photostabilization of poly(vinyl chloride)—still on the run. J Taibah Univ Sci 9:421–448 31. Winzinger A (1996) Unique rheology control additive for PVC plastisols. Brighton 32. Wegmann A, Oertli AG, Voigt W (2002) New additive solutions for the PVC industry. In: Compounding polyvinyl chloride in the 21st century. Brookfield 33. Lee RE, Pearson K (2002) Stabilization of polyvinyl chloride against oxidation. In: Compounding polyvinyl chloride in the 21st century. Brookfield 34. Falter JA, Geick KS, Williams JB (1997) Anti-fog additives for extruded film. In: Polymers, laminations and coatings conference proceedings, Toronto 35. Patrick S (2004) PVC compounds and processing. Rapra Technol 176 36. Bahgat AA, Sayyah SM, Shalabi HS (1998) Electrical properties of pure PVC, in science and technology of polymers and advanced materials (Prasad PN, Kandil SH, Kafafi ZH (eds)). Springer, Boston, New York, pp 421–428 37. Mohan KR, Achari VBS, Rao VVRN, Sharma AK (2011) Electrical and optical properties of (PEMA/PVC) polymer blend electrolyte doped with NaClO4. Polym Test 30:881–886 38. Hasan BA, Saeed MA, Hasan AA (2012) Optical properties of poly vinyl chloride PVC films irradiated with beta and gamma-rays. Brit J Sci 7:14–28 39. Aleshin AN, Mironkov NB, Suvorov AV, Conklin JA, Su TM, Kaner RB (1996) Transport properties of ion-implanted and chemically doped polyaniline films. Phys Rev B 54:11638– 11643 40. Ogura K, Saino T, Nakayama M, Shiigi H (1997) The humidity dependence of the electrical conductivity of a soluble polyaniline–poly(vinyl alcohol) composite film. J Mater Chem 7:2363–2366 41. Devi CU, Sharma AK, Rao VVRN (2002) Electrical and optical properties of pure and silver nitrate-doped polyvinyl alcohol films. Mater Lett 56:167–174 42. Agarwal S, Sexena NS, Agrawal R, Saraswat VK (2013) Study of mechanical properties of polyvinyl chloride (PVC) and polystyrene (PS) polymers and their blends. AIP Conf Proc 1536:777–778 43. Levchik SV, Weil ED (2005) Overview of the recent literature on flame retardancy and smoke suppression in PVC. Polym Adv Technol 16:707–716

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44. Xu Q, Jin C, Zachar M, Majlingova A (2013) Test flammability of PVC wall panel with cone calorimetry. Procedia Eng 62:754–759 45. Dickens ED (1983) The fire performance of PVC. J Vinyl Technol 5:150–157 46. Coaker AW (2004) Fire and flame retardants for PVC. J Vinyl Addit Technol 9:108–115 47. Jasim MT, Nuawi MZ, Ziyad SS, Bahari AR (2014) Characterization of mechanical poperties using I-Kaz analysis method under steel ball excitation technique. J Appl Sci 14:3595–3603 48. Fordham JWL (1959) Stereoregulated polymerization in the free propagating species. I. Theory J Polym Sci Part A Polym Chem 39:321–334 49. Gouinlock EV (1975) The fusion of highly crystalline poly(vinyl chloride). J Polym Sci Part B Polym Phys 13:1533–1542 50. Terrailler FK-H (1969) Influence of the thermal prehistory on the properties of polyvinyl chloride. Macromol Phys Chem 127:1–33 51. Summers JW (1981) The nature of poly(vinyl chloride) crystallinity—the microdomain structure. J Vinyl Addit Technol 3:107–110 52. Gouinlock EV (1975) Degrees of order from X-ray diffraction in highly crystalline poly(vinyl chloride). J Polym Sci Part B Polym Phys 13:961–970 53. Ballard DGH, Burgess AN, Dekoninck JM, Roberts EA (1987) The ‘Crystallinity’ of PVC. Polymer 28:3–9 54. Manson JA, Iobst SA, Acosta R (1972) Preparation of poly(vinyl chloride) at low temperature by a photochemical method. J Polym Sci Part A Polym Chem 10:179–186 55. Soni PL, Geil PH, Collins EA (1981) Microdomain structure in plasticized PVC. J Macromol Sci Part B Phys 20:479–503 56. Feldman D, Barbalata A (1996) Synthetic polymers: technology, properties, applications. Chapman & Hall, London, p 351 57. Jakubowicz I, Yarahmadi N, Gevert T (1999) Effects of accelerated and natural ageing on plasticized polyvinyl chloride (PVC). Polym Degrad Stab 66:415–421 58. Roux G, Eurin PA (1981) Indentation test for predicting embrittlement of rigid PVC by weathering. J Macromol Sci Part B Phys 20:505–517 59. Gardette J-L, Lemaire J (1993) Prediction of the long-term outdoor weathering of poly(vinyl chloride). J Vinyl Addit Technol 15:113–117 60. Gardette J-L, Lemaire J (1997) Reversible discoloration effects in the photoaging of poly (vinyl chloride). J Vinyl Addit Technol 3:107–110 61. Feldman D (2002) Polymer weathering: photo-oxidation. J Polym Environ 10:163–173 62. Minsker KS, Kolesov SV, Zaĭkov GE (1988) Degradation and stabilization of vinyl-chloridebased polymers. Pergamon Press, Oxford, p 508 63. Yagoubi N, Baillet A, Legendre B, Rabaron A, Ferrier D (1994) b-radiation effects on PVC materials: methodology for studying chemical modifications. J Appl Polym Sci 54:1043–1048 64. Varshney L, Balan N, Choughule SV, Jothish PK, Krishnamurthy K (1996) Radiation degradation and frictional properties of gamma sterilized PVC (Copper-T). Radiat Phys Chem 47:649–651 65. Chengyun Q, Qijian W, Guangcun M, Binsong C, Yunsheng Z (1993) Study on commercial radiation sterilization of PVC infusion sets. Radiat Phys Chem 42:591–593 66. Swierz-Motysia B, Zimek Z, Bojarski J, Przybytniak G, Sadto J (1999) Radution effects in PVC and PVC compositions. Radiat Chem Phys Radiat Technol 31:54–56 67. Naimian F, Katbab AA, Nazokdast H (1994) Post-irradiation stability of polyvinyl chloride at sterilizing doses. Radiat Phys Chem 44:567–572 68. Luther DW, Linsky LA (1996) Improving gamma radiation resistance: medical grade, flexible clear PVC compounds. J Vinyl Addit Technol 2:190–192 69. Yu J, Sun L, Ma C, Qiao Y, Yao H (2016) Thermal degradation of PVC: a review. Waste Manage 48:300–314 70. Braun D (2004) PVC-origin, growth, and future. J Vinyl Addit Technol 7:168–176

Chapter 3

Characterization Techniques of Polyvinylchloride (PVC)/ Thermoplastic Nano-Blends Shweta Sharma, Ankush Parmar, and S. K. Mehta

Abstract Lately, the explicit field of macromolecular compounds has been revolutionized by thermoplastic materials. With the introduction of these intriguing adaptable materials, the domains of commodity polymers have taken a diverse route. Amidst all the commodity polymers, polyvinylchloride (PVC) has turned out to be a milestone and has managed to place itself ahead of all the known thermoplastic polymers. Keeping in mind the aforementioned facts, the chapter in its present form focuses on highlighting the imperative physicochemical attributes of PVC/thermoplastic nano-blends. A major emphasis has also been laid on the elucidating the varied state-of-the-art analytical techniques being used to decipher the intricate traits of this diverse material.




Keywords Thermoplastic materials Polyvinylchloride Characterization Analytical techniques





Nano-blends


Abbreviations AFM ASTM CaCO3 CdS CdS-PS/PVCnc CHNSO CNTs CTE

Atomic force microscopy American Society for Testing and Materials Calcium carbonate Cadmium sulfide Cadmium sulfide embedded polystyrene/polyvinylchloride nanocomposites Carbon, hydrogen, nitrogen, sodium, and oxygen (element analyzer) Carbon nanotubes Coefficient of thermal expansion

S. Sharma (&)
A. Parmar Institute of Forensic Science and Criminology, Panjab University, Chandigarh 160014, India e-mail: [email protected] S. K. Mehta Department of Chemistry and Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh 160014, India e-mail: [email protected] © Springer Nature Switzerland AG 2022 V. P. M. and R. N. Darie-Nita (eds.), Polyvinylchloride-based Blends, Springer Series on Polymer and Composite Materials, https://doi.org/10.1007/978-3-030-78455-3_3

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DCP DSC DiTA DLS DMA DMTA DOP DTA Dt FT-IR G’ G” G”/G’ KIc LDHs LOI MAP-POSS MMT MPa MS n Na+ MMT NCD NMR oMMT PCL PCS PS PS/PVC PVC PVC-Nb PVC-SWNTs SAXS SEM SWNTs TEM Tg TGA TMA UL-94 UV-Vis WAXD WAXS XRD

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Disk centrifuge photodimentometry Differential scanning calorimetry Dielectric thermal analysis Dynamic light scattering Dynamic mechanical analysis Dynamic mechanical thermal analysis Dioctyl phthalate Differential thermal analysis Degradation temperature Fourier transform infrared spectroscopy Young’s modulus Loss modulus Tan d Stress intensity factor Layered double hydroxides Limiting oxygen index Methylacrylopropyl groups Montmorillonite Mega Pascal Mass spectroscopy Newtonian index Sodium montmorillonite Non crystalline diffraction Nuclear magnetic resonance Organophilic montmorillonite Poly (e-caprolactone) Photo correlation spectroscopy Polystyrene Polystyrene/Polyvinylchloride Poly vinyl chloride Polyblends nanocomposites Polyvinylchloride single-walled carbon nanotube composites Small angle X-ray scattering Scanning electron microscopy Single-walled carbon nanotube composites Transmission electron microscopy Glass transition temperature Thermo-gravimetric analysis Thermo-mechanical analysis Underwriters laboratory test # 94 Ultraviolet visible spectroscopy Wide angle X-ray diffraction Wide angle X-ray scattering X-ray diffraction

3 Characterization Techniques of Polyvinylchloride (PVC) …

XRF XPS ZnO iw cw

3.1

51

X-ray fluorescence X-ray photoelectron spectroscopy Zinc oxide Shear stress Shear rate

Introduction

Besides other commodity polymers, viz. polyethylene and polystyrene, poly(vinyl chloride), better known by its abbreviation, PVC is a standout among the most widely recognized thermoplastic materials utilized today, with applications running from packaging to medicinal services gadgets, toys, electrical wire protection, garments, furniture, interior decoration, building materials, and the auto business [1]. It positions second among the most utilized thermoplastics and is viewed as the most adaptable macromolecular compound. Its adaptability emerges from its appropriateness to a variety of transformations. Its fundamental disadvantage is the low thermal stability that prompts discoloration due to the formation of conjugated polyene sequences [2]. The addition of mineral nano-fillers to organic macromolecular mixes including PVC has brought about polymer nanocomposites characterized by lightweight, low-cost, and improvised properties. The adding to PVC alongside the nano-filler another thermoplastic polymer, an elastomer, or even wood flour can contribute fundamentally to the improvement of PVC properties. In some cases, a second polymer may cover the surface of the nano-filler particles augmenting the interaction of PVC nano-filler [1, 2]. Before moving ahead, it becomes imperative to clarify the term blends/ composites before the discussion of nanocomposites in light of the fact that it is fairly equivocal to distinguish whether the materials fall into the category of these minuscule composites or not. In the meantime, utilization of the word nanocomposites suggests that materials comprise different compositions with various phases, and no less than one constituent phase has one dimension in the range of 10–2– 10–9 m or above [2]. The poly blends nanocomposites (10–9 m) based on PVC (PVC-Nb) can be defined as the composites of polymers with dispersed inorganic nano-fillers. The nano-fillers can be a cover, a semiconductor, or a metal, and it can have spherical, elliptical, or cylindrical geometry. The polymer (grid) can be conductive or non-conductive in nature. Generally, the following nano-fillers are regularly utilized [2]: • • • • •

montmorillonite (MMT) sodium montmorillonite (Na+ MMT) organophilic montmorillonite (oMMT) calcium carbonate (CaCO3) silica talc

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• layered double hydroxides (LDHs) • organo-modified clays, viz. laponite, bentonite, hectorite, kalonite, and halloysite • carbon nanotubes (CNTs) A low amount of nano-filler dispersed in the polymer lattice can prompt a high surface area of interaction. So depending on it, we can get diverse nanostructures of polymer nano-filler composites [2]; • Intercalated nanocomposites: They are the ones which are obtained by seating the polymeric macromolecules between the filler layers. • Exfoliated nanocomposites: The individual layers of the filler are absolutely delaminated and dispersed in a persistent polymer lattice. • Intermediate polymer nanocomposites: These types of nanocomposites depict partial intercalation and exfoliation. To create polymer nanocomposites intercalated or exfoliated, numerous strategies are accessible, for example, in situ polymerization, solution dispersion, and melt mixing. The type, amount of nano-filler, and the fabrication strategy influence the principle properties of polymer nanocomposites through the delamination and exfoliation levels [2]. The upcoming section will emphasize on enlisting the basic definitions and common terminologies associated with the preface of the chapter.

3.2

Overview of Physicochemical Characteristics

Numerous state-of-the-art techniques have been inculcated for a comprehensive assessment and effectual characterization of varied physicochemical properties (viz. stereochemistry, particle size distribution profile, surface charge, morphology and surface geometry, etc.) of the PVC-Nb. Among these plentiful techniques, some of them offers lucrative analytical characterization of intrinsic properties which are distinct for a particular class of PVC-Nb. Further, the recent era has witnessed a remarkable utilization of hyphenated techniques to invigorate the structure property relationships of PVC-Nb. It has been established that the properties of PVC-Nb have a strong correlation with the innate characteristics (viz. composition, interfacial interaction, particle size, etc.) of the parent excipients from which they have been synthesized. The characterization parameters used to elucidate the varied properties of PVC-Nb are correspondingly discussed. (i) Chemical Structure/Stereochemistry Solid-state spectroscopy, viz. Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), mass spectroscopy (MS), ultraviolet visible spectroscopy (UV–Vis), and Raman spectroscopy and elemental analyzer (CHNSO) have been employed for deciphering the chemical structure and stereochemistry of PVC-Nb.

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(ii) Size distribution profile Dynamic light scattering (DLS), photo correlation spectroscopy (PCS), quasi-elastic light scattering, and disk centrifuge photodimentometry (DCP) have been utilized for modeling the size distribution profile of PVC-Nb. The former technique is governed by Stoke’s Einstein equation and gives an average diameter based upon intensity, while on the other hand, DCP reports an average diameter based upon weight. (iii) Surface charge/zeta potential and morphology The surface topography/morphology of PVC-Nb has been elucidated on a wider front via scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM), while the surface charge of the polymeric/thermoplastic composite blends has been demonstrated by zeta size analyzer. (iv) Geometry/elemental composition Crystallization behavior of PVC-Tb is usually identified by X-ray techniques, viz. X-ray diffraction (XRD) and X-ray fluorescence (XRF), and calorimetric techniques, viz. differential scanning calorimetry (DSC). (v) Mechanical properties In order to enhance the mechanical properties, some inorganic fillers are added to the existing polymeric mixture which imparts an equilibrium between the strength and toughness. Hence, characterization of mechanical properties (viz. tensile strength, impact resistance, flexural properties, hardness, fracture toughness, friction, and wear properties) of PVC-Nb becomes extremely vital for scientific domain. Tensile impact and flexural properties Three parameters, viz. tensile strength, Young’s modulus, and elongation at break have proven to be a triumphant tool for comprehensively assessing the qualitative and quantitative properties of PVC-Nb. Hardness Hardness may be defined as the inherent property to resist a change in the geometry or intermolecular arrangement of a material, on an application of shear force. It becomes an underlying basic phenomenon for assessing and governing the absolute mechanical properties and applications of PVC-Nb. Depending upon the direction, type, and amount of force applied, hardness can be chiefly classified in three major categories, viz. • Scratch hardness (when a certain amount of force is applied from a sharp object, a resistance is provided by counteracting the fracture and plastic deformation) • Indentation hardness (when a substance faces a blunt trauma from a sharp object, a resistance is provided by counteracting the plastic deformation) • Rebound hardness

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Fracture toughness Fracture toughness is a property that depicts the capacity of a material containing a crack to oppose fracture. Among all the characteristics properties of a material, fracture toughness accounts for the most imperative one. Numerous methods such as single-edge notch bend and indentation fracture toughness have been employed for computing the fracture toughness indices of varied materials. The fracture toughness of PVC-Nb is evaluated by computing the stress intensity factor. It can be taken into consideration that as the stress intensity factor figure comes to a critical value (KIc), an unstable fracture takes place. The KIc value thus calculated denotes a brief intervention of the fracture resistance and is abbreviated as fracture toughness of the material. Friction and wear properties Both the terms friction and wear properties can be connoted under a single terminology, viz. tribology. Friction is the drive of two surfaces in contact or constrain of a medium following up on a moving item, and wear is the disintegration of material from a strong surface by the activity of another strong. Particle size, morphology, and concentration of the filler are some of the factors which impedes an influence on the friction and wear traits of PVC-Nb. (vi) Thermal properties Thermal properties are the ones which changes with an alteration in the niche temperature. Quite a few techniques such as differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA), differential thermal analysis (DTA), thermo-mechanical analysis (TMA), dynamic mechanical analysis (DMA), dynamic mechanical thermal analysis (DMTA), and dielectric thermal analysis have been utilized to revamp the thermal properties. Among all of these TGA, DTA, and DSC are the notable analytical techniques whose utilization has been carried out on an expansive front to decipher the thermal properties of PVC-Nb. Table 3.1 enlists the characteristic properties attained from varied analytical techniques. (vii) Flame-retardant properties A fire retardant is utilized to make materials harder to ignition by moderating disintegration and expanding the ignition temperature. It capacities by different techniques, for example, retaining energy away far from the fire or averting oxygen from achieving the accelerant. The combustibility conduct of polymer is characterized on the premise of a few procedures or parameters, for example, rate of burning, rate of spread, characteristic of ignition, and so on. Limiting oxygen index also commonly known as LOI (is defined as the measure of the minimal fraction of O2 imbibed in a binary mixture of O2 and N2 required to suffice flame-induced combustion) serves as the credential for assessing the flame-retardant characteristics of PVC-Tb. Apart from this, another test known as UL-94 (Underwriter’s Laboratory Test # 94) is conducted to assess the flame-retardant properties of polymeric composites in horizontal and vertical plane.

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Table 3.1 Characterization parameters attained from analytical techniques Technique

Characterization parameters

TGA

Stability Drug degradation onset Percentage composition of intercalated molecules into the matrix Thermal transition behavior Coefficient of thermal expansion (CTE) Dimensional stability assessment Viscoelastic behavior Young’s modulus (G’) Loss modulus (G”) tan d (G”/G’) Glass transition temperature (Tg) Molecular mobility transition Viscoelastic behavior

DSC TMA DMA/DMTA

Dielectric thermal analysis

The horizontal burning test employs Bunsen burner as the primary ignition source and the samples are chiefly classified into four major categories, viz. V0 (best), V1, V2, or non-classifiable (fail) as a function of their respective ignition time. While in vertical burning test, the samples are chiefly classified into two prominent categories, viz. HB or fail. As compared to vertical test, a lesser amount of severity is pronounced in case of horizontal burning test. A number of parameters such as rate of fire spread across the horizontal plane, behavior of burning, and the ease with which the material got extinguished are exclusively revealed from the horizontal test. Additionally, cone calorimeter is considered to be a bench mark technique for the assessment of flame-retardant properties. This technique felicitates the scientific realm to extract vital information about the rate of heat and peak heat release from the PVC-Nb. (viii) Optical properties Transparency and refractive index formulates the two most vital optical properties which can be computed via using an instrument known as refractometer. (ix) Gas transport properties Solubility, diffusivity, permeability, and permi-selectivity are some of the properties which can be correlated with the gas transport phenomenon occurring in PVC-Nb. Numerous techniques have been used to determine the gas transport properties of composites. For example, cup method (ASTM D1653-93) was encouraged to estimate the permeability of thermally sprayed coatings.

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(x) Rheological properties Rheology is the investigation of deformation and flow of matter affected by an applied stress. In order to predict the physical properties of PVC-Nb, the computation of rheological properties becomes obligatory. For instance, Oberdisse piloted uniaxial strain experiments to decrypt the rheological properties of special nanocomposites material. (xi) Electrical properties Dielectricity, conductivity, and percolation threshold are some of the terms which collectively label the several electrical characteristics of the PVC-Nb.

3.3

Modalities for Physicochemical Characterization

Propels in PVC-Nb have opened up another time of finding, aversion, and treatment of diseases and traumatic injuries. PVC-Nb, incorporating those with potential for clinical applications, have novel physicochemical properties that affect their physiological associations, from the atomic level to the systemic level. There is an absence of standardized methodologies or regulatory protocols for detection or characterization of PVC-Nb. This chapter abridges the analytical techniques that are generally used to decipher the size, shape, surface properties, composition, purity, and intrinsic stability of PVC-Nb, alongside their points of interest and conflicts. There is a critical requirement for standardized conventions and methodologies for the characterization of PVC-Nb, particularly those that are proposed for human application. Characterization of PVC-Nb depends on the assessment of physicochemical properties, for example, particle size, viscosity, hardness, and fracture toughness, etc. Numerous techniques that are routinely connected for characterization of traditional pharmaceuticals can likewise be utilized for characterization of PVC-Nb. However, a few particular attributes of subatomic size materials such as size, geometry, surface charge, and shape are basically critical and should be very much explored to better understand nanomaterials’ practices in real-time application. Tended to underneath are brief depictions of modalities used to examine the particular physicochemical properties of subatomic-sized materials, and their primary qualities and restrictions for polymeric blends examination. (i) Mechanical Properties Preparation method and mechanical properties are two imperative factors which tends to play a seminal function in shaping the morphological parameters of polymeric blends. The morphological parameters of blends are found to be influenced by these prime factors, namely modulus (elastic modulus, storage modulus, flexural modulus, and Young's modulus), strength (tensile and impact), percentage strain, Charpy impact, elongation at break, abrasion resistance, fracture energy, ultimate tensile stress, fracture energy, texture analysis, etc.

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An elaborative study was conducted by Arya et al. [3] for assessing the thermo-mechanical performance of PVC/ZnO nanocomposites. The study focused on determining the intrinsic effect of temperature on the viscosity profile of nanocomposites. During the initial phase, a sharp incline in viscosity was exhibited with steep rise in temperature; however, a further increase in temperature leads to the attainment of a constant value. Another, interesting finding was the dependence of viscosity on the concentration of ZnO nano-fillers. An enhancement in the content of ZnO nano-filler content up to 6% w/w resulted in a gradual increase in the viscosity profile of PVC/ZnO nanocomposites. A further increase in the nano-filler content up to 8% w/w resulted in a decline in the viscosity profile values [3]. The augmentation in the viscoelastic properties of PVC/ZnO nanocomposites obviously shows the phenomenal dispersion of ZnO nanoparticles in PVC framework. Further, a reduction in the value of observed properties with higher filler content (8 wt.%) demonstrates that agglomeration of nanoparticles is incited in polymer matrix. This recommends the lower dispersion capacity of ZnO nanocrystals at higher wt.%. This agglomeration augments the particle–particle interaction over particle–polymer interaction at higher wt. % (8 wt.%) of nanoparticles, thereby increasing heterogeneity and versatility of polymer chains in the system [3]. Organically modified clays (nano-fillers)-based nanocomposites of PVC were prepared by Awad et al. [4]. They utilized a tensile tester to evaluate and comprehensively assess the room temperature mechanical properties of reinforced nanocomposites and pristine PVC. It can be visualized from Table 3.2 that the addition of nano-clay did not produce any marked alteration in the yield point of nanocomposites. Further, an augmentation in the tensile modulus was observed in case of composites comprising of nano-sized fillers. In addition, these impacts are not exactly as articulated for the tensile properties when plasticizer and dispersants were added to the nanocomposites; however, the trend remained the same for the most part. To be specific, the moduli of nanocomposites appeared to increase as compared to unfilled or pristine PVC. In the meantime, the tensile strength remains the same for all composites at around 45 MPa, somewhat larger than the unfilled or pristine PVC framework (the plasticized PVC has a tensile strength of around 43 MPa; Table 3.2). After thermal aging at 80 °C for 7 days, this behavior was maintained, i.e., all composites have practically identical tensile strength values (around 40 MPa: Table 3.3), and, not surprisingly, all strengths were found to be marginally lower than before thermal aging [4]. (ii) Dynamic mechanical analysis The viscoelastic behavior of the polymeric blends is envisaged via employing dynamic mechanical analysis (DMA). In this analytical protocol, the sample specimen is imposed to undergo a sinusoidal stress, and the strain is calculated to decipher the complex modulus of the material under consideration. Xie et al. [5] performed in situ polymerization of polyvinylchloride in the presence of calcium carbonate (CaCO3) nanoparticles for the facile fabrication of PVC/CaCO3 nanocomposites. In their experiment, variation in storage modulus (Fig. 3.1a) and

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Table 3.2 Mechanical properties of PVC and PVC nanocomposites before aging (Reproduced with permissions from [4]) Compound

Yield point Tensile stress at max loada (MPa)

PVC 49.4 PVC + Talc 49.4 PVC + Kaolin 48.2 PVC + Bentonite 49.0 PVC + Hectorite 49.8 a Measured at 250 mm/min b Measured at 50 mm/min

Tensile stress at max loadb (MPa)

Tensile strain at max loada (MPa)

49.3 48.9 47.4 47.6 48.8

3.7 3.8 3.6 3.3 3.6

Modulus Young’s modulusa (MPa)

Young’s modulusb (MPa)

G’ at 30 °C (MPa)

2390 2273 2248 2797 2724

1518 1577 1567 1723 1765

899 910 988 1080 956

Table 3.3 Effect of dispersant on the tensile properties (250 mm/s) of PVC composites before aging (Reproduced with permissions from [4]) Compound

Tensile modulus (MPa)

Tensile strength (MPa)

Elongation at break (%)

PVC PVC PVC PVC PVC PVC PVC PVC PVC PVC PVC

2390 2031 1920 2230 2172 2037 1930 2051 2243 2249 2166

49.4 43.2 44.9 45.7 45.0 45.2 42.4 44.4 45.5 46.3 45.9

32 43 44 44 35 37 75 40 36 39 27

+ + + + + + + + + +

Plasticizer Plasticizer Plasticizer Plasticizer Plasticizer Plasticizer Plasticizer Plasticizer Plasticizer Plasticizer

+ + + + + + + + +

hectorite bentonite hectorite bentonite dispersant dispersant dispersant dispersant dispersant

+ + + +

hectorite bentonite hectorite bentonite

loss factor (tan d) (Fig. 3.1b) as a function of temperature was probed by performing the DMA of the fabricated nanocomposites. The comparative DMA analysis showed that the PVC/CaCO3 nanocomposites had a greater storage modulus as compared to pristine PVC. Further, the storage modulus of PVC/CaCO3 nanocomposites was found to be amplified by approximately 18% with an increase in the content of CaCO3 nano-fillers. Hence, corroborating the fact that nano-filler loading can enhance the stiffening of PVC matrix. Another trend which got revealed during the course of experimentation was the progressive reduction in storage modulus of nanocomposites with increasing temperature.

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Fig. 3.1 a Variation of storage modulus, b tan d with temperature for pristine PVC and nanocomposites (Reproduced with permissions from [5])

Xie et al. further extended their study to compute the loss factor as a function of temperature. It was deciphered from DMA that an augmentation in the value of tan d was noticed for pristine PVC, while the PVC/CaCO3 nanocomposites showed the lowest values for loss factor. Additionally, an inverse correlation was seen between the nano-filler content and tan d. The value of loss factor decreased with an increase in the content of CaCO3 nano-fillers. The height dejection in the tan d peak is due to reduction in the amount of mobile polymer chains during the phase transition and virtuous adhesion between the polymer and nanoparticles. (iii) Thermo-gravimetric analysis Thermo-gravimetric analysis (TGA) is one of the other routine techniques used for polymer characterization. It can be summarized as a thermo-analytical technique which perceives any alteration in the chemical or physical attribute of a material as a function of escalating temperature (with constant heating rate), or isothermally as a function of time in an inert atmosphere or vacuum. The glass transition temperature commonly abbreviated as Tg can also be determined using TGA. Tg can in turn aid in the evaluation and identification of possible transitions taking place as a function of molecular motions. Madaleno et al. [6] prepared PVC/MMT, PVC/Na-MMT nanocomposites via solution blending and solution blending coupled with melt compounding methodology. In their study, they deduced the morphological, thermal, and mechanical characteristics of the formulated nanocomposites. TGA analysis was conferred to exemplify the thermal behavior, TG, and DTG curves of pristine PVC and PVC-based nanocomposites. Thermo-gravimetric investigation uncovered that PVC/Na-MMT nanocomposites possessed augmented thermal stability over PVC/ OMMT nanocomposites and pristine PVC (Fig. 3.2a, b). In general, PVC/MMT nanocomposites primed solution blending and melt compounding uncovered

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Fig. 3.2 a Thermogram of PVC and PVC/Na-MMT nanocomposites; b PVC and PVC/OMMT nanocomposites (Reproduced with permissions from [6])

enhanced thermal properties as compared to PVC/MMT nanocomposites fabricated by solution blending [6]. Organically modified clays (nano-fillers), viz. hectorite and bentonite-based nanocomposites of PVC were prepared by Awad et al. [4]. The thermal stability of the composites was assessed using a standard thermo-gravimetric analysis. Thermo-gravimetric investigation (TGA) has been utilized to relatively assess the thermal deterioration of PVC and its composites, a behavior that has been shown to correlate directly to the dispersion of nano-clay in a polymeric framework. The TGA analysis revealed that no significant influence on the peak degradation temperature (Dt) of the nanocomposites was observed after addition of the fillers. Perhaps a marginal drop in the Dt was observed along with the addition of nano-clay. Further, a catalytic effect was portrayed as the addition of nano-clay seems to accelerate the rate of degradation process. However, this trend does not appear to be equivalent over the complete span of degradation [4]. (iv) Differential scanning calorimetry Differential examining calorimetry (DSC) is one of the standard techniques utilized as a part of polymer characterization and enhances the information of the microphase structure with other corresponding techniques. DSC is a thermo-analytical technique in which the distinction in the amount of heat required to increase the temperature of a specimen and reference is measured as a function of temperature. Polyvinylchloride single-walled carbon nanotube composites (PVC-SWNTs) were fabricated by Chipara et al. [7]. Their study was primarily focused on investigating the thermal and spectroscopic properties of the formulated nanocomposites. DSC studies were performed to envisage the intermolecular interactions taking place between PVC and nano-fillers. DSC analysis revealed an augmentation in the glass transition (Tg) temperature of the polymeric matrix with the loading of PVC-SWNTs (Fig. 3.3a). It was noticed that an increment in SWNTs

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Fig. 3.3 DSC data on PVC-SWNT nanocomposites showing the effect of the loading with SWNTs. The inset shows the dependence of the glass transition on the concentration of SWNTs (Reproduced with permissions from [7])

content from 0 to 20% w/w leads to an increase in the Tg about 10 °C. This can be ascribed to the generation of intermolecular interactions taking place between the molecular chain and nano-filler [7]. Huang and Wang [8] devised a novel methodology to construct polyvinylchloride nanocomposites reinforced with MgAl layered double hydroxide (LDH) and intercalated with lauryl ether phosphate. It was revealed from the DSC analysis that the nanocomposites exhibited a slightly lower Tg than the PVC pristine (Fig. 3.4). This can be ascribed to the fact that the existing intermolecular interactions in the nanodispersion were rendered due to LDH layers owing to which the PVC macromolecules were segregated apart from each other. Moreover, it is conceivable that the PVC lattice was marginally plasticized by some of lauryl ether phosphate, and this brought about the decline of the Tg of PVC phases [8]. (v) Atomic force microscopy Atomic force microscopy (AFM) is an effective technique that can be utilized to acquire both high-resolution pictures on numerous sorts of solid surfaces and the vertical force and also parallel force between a sharp tip and the surface. Subatomic-scaled AFM can be used for the quantitative assessment of viscoelastic parameters of polymeric blends. A two-step reaction was employed by Mondragon et al. [9] to prime PVC/poly (e-caprolactone) (PCL)/organophilic montmorillonite (OMMT) and PVC/ poly-lactide (PLA)/OMMT nanocomposites. Atomic force microscopy was employed to investigate the morphological properties of all the fabricated nanocomposites. The AFM images clearly revealed that the MMT particles were well dispersed within the corona or the polymeric matrix of all the nanocomposites containing 3% w/w clay. PVC/PCL/OMMT nanocomposites exhibited excellent

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Fig. 3.4 DSC curves of PVC and PVC/LDH nanocomposites with different loading of LDH (Reproduced with permissions from [8])

adhesion property as the OMMT particles were found to be well established within the PVC/PCL matrix, while a retrogressive trend was portrayed by PVC/OMMT and PVC/PLA/OMMT nanocomposites. These nanocomposites exhibited poor adhesion property as the OMMT particles were found to be loosely seated in the polymeric matrix. These results also corroborated the fact that the tensile strength and stiffness were dependent upon two prominent factors, viz. clay dispersion and adhesion between MTT and polymeric matrix [9]. Yalcin and Cakmak [10] assessed the role of plasticizer on exfoliation, dispersion, and fracture behavior of PVC/clay nanocomposites via conducting a comprehensive morphological study. AFM analysis was performed on these nanocomposites to probe the spatial distribution of these systems (Fig. 3.5). The clay nanoparticles were promptly scattered and shed in the PVC network with the assistance of dioctyl phthalate (DOP) plasticizer. AFM examination of the nanocomposites shows that there is an ideal grouping of DOP for the procedure. The individual platy MMT particles scattered in PVC lattice were specifically seen by AFM and found to lie preferentially on their basal surfaces, particularly when the compounded batch is compression molded. Further, AFM analysis showed that the edges of the nanocomposites in few cases were straight and hexagonally shaped, while remaining ones were sporadic or irregularly shaped [10]. (vi) Transmission electron microscopy Transmission electron microscopy (TEM) is another technique of paramount importance which can give an insight about the morphological and auxiliary characteristics of polymer blends. TEM could give pictures altogether of higher resolution than a light microscope by utilizing electrons as ‘light source’ which have a much lower wavelength. The underlying principle is that a light emission goes through an extremely thin specimen, and, subsequent to interacting with the atoms of the sample specimen, some ejected unscattered electrons are gathered to frame an image on the fluorescent screen. Organically modified clays (nanofillers), viz. hectorite and bentonite-based nanocomposites of PVC were prepared by Awad et al. [4]. Transmission electron

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Fig. 3.5 AFM phase image of plasticized PVC nanocomposite (10-wt% clay loading and 70 PHR DOP) (Reproduced with permissions from [10])

microscopy coupled with bright field emission was employed for characterizing the morphology of these formulated systems. TEM analysis demonstrated that the formulations were intercalated and exfoliated-type systems which further exhibited a true nanocomposite nature (Fig. 3.6a–d). It became evident from the TEM analysis that hectorite and bentonite were found in a well-dispersed nano-sized state. In addition to this, it was concluded from TEM that the dispersion of nano-fillers within the corona of the polymeric PVC matrix was found to be affected by the content of plasticizer and dispersant. Further, the TEM analysis indicated toward the excellent dispersion property of both clays to undergo size reduction at nanoscale without losing their structural integrity (parallel stacking). Lastly, in all cases the structure of the composites

Fig. 3.6 a and b TEM monographs of PVC–hectorite nanocomposites containing a dispersant; c and d the TEM images of nanocomposite containing only PVC and organically modified clay (Reproduced with permissions from [4])

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possessed a blended morphology of exfoliated and what is more seems like scattered nano-clay fillers, with varieties in degree of scattering from system to system [4]. Yalcin and Cakmak [10] assessed the role of plasticizer on exfoliation, dispersion, and fracture behavior of PVC/clay nanocomposites via conducting a comprehensive morphological study. TEM analysis was performed on these nanocomposites to probe the spatial distribution of these systems. Having established that the platelets are scattered as a deck of cards tossed upon a table with their basal surface normals pointed toward the direction of thickness, TEM pictures ought showed clear submicron length edges (Fig. 3.7a, b). It was wonderful that indeed, even at high clay content, no critical conglomeration was obvious. Nonetheless, numerous areas with a tactoid nature were display. The thickness of the edges being greater than 1 nm suggested that the observed layers were composed of various elementary layers stacked on top of each other, whereas at the point when the content of plasticizer, viz. dioctyl phthalate (DOP) was expanded an improvisation in the critical quality attribute of the dispersion took place along with a pronounced reduction in the thickness of the individual layer (less stacking) [10]. (vii) Scanning electron microscopy Scanning electron microscopy (SEM) is one of the exceptionally helpful microscopic techniques which can be utilized for the morphological and auxiliary examination of composite materials. The characteristic features like shape, structure, and conductivity are determined by irradiating the surface of the sample specimen with a focused beam of high-energy electrons. Subsequent to interacting with the atoms of the sample specimen, some ejected unscattered electrons are gathered to frame an image on the fluorescent screen. An elaborative study was performed by Arya et al. [3] for assessing the thermo-mechanical performance of PVC/ZnO nanocomposites. During this study, an extensive investigation of structural properties of nanocomposites was carried out via engaging SEM technique. The structural characterization study revealed a

Fig. 3.7 TEM micrographs depicting the PVC nanocomposite systems a with 10% w/w clay; b 4% w/w clay at 30 phr DOP loading (Reproduced with permissions from [10])

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possible composition-dependent alteration in the morphology of nanocomposites as compared to pristine PVC. As revealed by SEM analysis, the morphology of the pristine PVC specimens was found to be altered on facile addition of nano-sized ZnO fillers. Pristine PVC specimen devoid of ZnO nano-fillers possessed a highly porous and granular topography, while ZnO-doped PVC nanocomposites portrayed a highly smoother topography. Further PVC/ZnO nanocomposites exhibited a compacted amorphous surface morphology which was found to be increasing when the doping content of ZnO fillers was escalated upto 6% w/w. However, on further adding the ZnO fillers upto 8% w/w, some intermittent interfaces were found to be originating [3]. Madaleno et al. [6] prepared PVC/MMT nanocomposites via solution blending and solution blending coupled with melt compounding methodology. In their study, they deduced the morphological, thermal, and mechanical characteristics of the formulated nanocomposites. The PVC/MMT nanocomposites were imposed to undergo SEM analysis for the pronouncement of any possible intercalation and exfoliation existing in the nanostructure (Fig. 3.8a–d). Further the quality of nanoclay dispersion in nanocomposites was quantified on the basis of SEM. The SEM data analysis revealed that the nanocomposite specimens were devoid of any conglomeration. This, in turn, highlighted the probabilistic existence of delamination and intercalation/exfoliation throughout the plates existing in the polymeric matrix [6]. Xie et al. [5] performed in situ polymerization of polyvinylchloride in the presence of calcium carbonate (CaCO3) nanoparticles for the facile fabrication of PVC/CaCO3 nanocomposites. In their experiment, fracture surface analysis

Fig. 3.8 a and b SEM monographs of PVC/Na-MMT nanocomposites prepared by solution blending and solution blending + melt compounding; c and d SEM monographs of PVC/OMMT nanocomposites prepared by solution blending and solution blending + melt compounding (Reproduced with permissions from [6])

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(fracture micro-mechanisms) was performed by probing the nanocomposites with scanning electron microscopy (Fig. 3.9a–c). It was portrayed from the fracture micro-mechanism studies that the PVC/CaCO3 nanocomposites were malleable and possessed ductile characteristics as compared to pristine PVC which was brittle in nature. Further, SEM analysis established that the PVC/CaCO3 nanocomposites had a rough fracture surface and as a consequence of interface debonding a small number of elliptical voids existed around the halo of CaCO3 nanocomposites [5]. (vii) Rheological measurements Rheology estimations are significantly imperative for plastics engineers also as to polymer rheologists. Rheology is the investigation of flow and deformation of materials under applied forces which is routinely measured utilizing a rheometer. The estimation of rheological properties is relevant to all materials—from fluids, for example, dilute solutions of polymers, to semi-solids, for example, glues and creams. Rheological properties can be measured from bulk specimen disfigurement utilizing a mechanical rheometer, or on a miniaturized scale by utilizing a micro-capillary viscometer or an optical procedure, for example, micro-rheology. Cases of rheological measurements include (a) viscosity profiling for non-Newtonian shear-dependent behavior to simulate processing or in-use conditions. (b) viscoelastic fingerprinting for material classification to determine extent of solid-like or liquid-like behavior. (c) optimizing and assessing dispersion stability. (d) determination of thixotropy of paints and coatings for product application and final finish quality. (e) impact of molecular architecture of polymers on viscoelasticity for processing and end-use performance. (f) full cure profiling for bonding or gelling systems. (g) pre-formulation screening for therapeutics, particularly prosthetics.

Fig. 3.9 SEM micrographs depicting the longitudinally cryogenic-fractured necked region of a pure PVC; b 5 wt% nano-CaCO3; c 7.5 wt% nano-CaCO3 (Reproduced with permissions from [5])

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Gao et al. [11] synthesized PVC-based nanocomposites intercalated with polyhedral oligomeric silsesquioxanes containing methylacrylopropyl groups (MAP-POSS). Capillary rheometer was engulfed for envisaging the rheological characteristics of the PVC/MAP-POSS nanocomposites. The rheological behavior data revealed the dependence of essential parameters, viz. shear stress (iw) and shear rate (cw) and Newtonian index (n) on the MAP-POSS concentration. It was deciphered from the study that an escalated level of MAP-POSS concentration will lead to the generation of low shear stress, shear rate, and higher Newtonian character. However, when the level of cw was increased, a lower degree of shear-thinning behavior was observed in case of MAP-POSS/PVC nanocomposites as compared to pure PVC. Further, a shear-thinning pseudo-elastic flow with increasing shear rate was portrayed by melted PVC devoid of MAP-POSS [11]. Additionally, the rheological behavior analysis highlighted a direct correlation between the Newtonian index (n) and MAP-POSS concentration. It was clearly depicted from the study that the value of Newtonian index increased with an increase in the concentration of MAP-POSS to a maximal extent until the MAP-POSS content does not exceed beyond 5%. When the MAP-POSS concentration was extended beyond this fixed percentage, a potential decline in the value of Newtonian index was portrayed. These results clearly demarcated that a decline in the MAP-POSS content will result in the significant reduction of pseudo-elastic (non-Newtonian) fluid behavior [11]. Another congruent study was conducted by Gao et al. [12] on PVC nanocomposites intercalated with vinyl-grafted POSS (PVC/V-POSS). Torque and capillary rheometer was employed for the portrayal of rheological behavior of nanocomposites. This study focused on the thorough investigation of the effect of blend, shear rate, and shear stress on non-Newtonian index. Obtained results were found to be consistent with the previous study on PVC/MAP-POSS. The rheological behavioral analysis indicated an enhancement in the pseudo-plastic fluid behavior of the nanocomposite with an increase in the V-POSS content [12]. (ix) Diffusion properties The translocation of gasses and liquids through polymeric membranes is caused by either along a pressure, concentration and/or temperature gradient, or by an externally applied force. The pervasion of gasses through polymer is normally governed by ‘solution diffusion’ mechanism. It comprises of the accompanying strides; (a) absorption of small molecules into the membrane along the edge of higher potential (pressure, concentration, and so forth). (b) molecular diffusion of the particles in and through the polymeric matrix. (c) desorption (release) of the diffused atoms from the arrangement at the inverse side into the liquid or gas stage at lower potential. In a study, Mohagheghian et al. [13] employed thermal phase inversion coupled with sol–gel methodology to fabricate PVC/silica nanocomposite membranes.

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Further, they investigated the diffusion properties of these nanocomposite-based membranes to separate oxygen, nitrogen, and carbon dioxide gases. Additionally, time lag protocol was taken into consideration to evaluate the diffusion coefficient of these PVC/silica nanocomposite membranes. The permeability studies (based on volume-variable pressure method) on pristine PVC membrane and PVC/silica nanocomposite membrane revealed that the addition of silica nanoparticles into the PVC matrix felicitated an enhanced and improvised separation potential of gases (Fig. 3.10a), hence indicating toward a superior diffusion performance by PVC/ silica nanocomposite membrane as compared to pristine PVC composites [13]. Further, impregnation of silica particles in the polymeric matrix of PVC resulted in the establishment of intermolecular polar voids at the junction between the particles within the polymeric matrix. This was attributed to the augmentation in the density of polar OH groups within the polymeric matrix as a consequence of increased silica mass fraction. Additionally, the establishment of intermolecular polar voids leads to an enhanced solubility and diffusion coefficient (Fig. 3.10b), thereby allowing the more polar gases to pass through them at a much faster rate [13]. Sadek et al. [14] synthesized PVC/layered silicate nanocomposites, and they premeditated the effect of organoclay type on the oxygen permeability of this plasticized PVC/clay nanocomposite (Fig. 3.11). An enhanced oxygen permeability was displayed by unfilled PVC at a relative humidity of 50%. This can be ascribed to the intermolecular hydrogen bonding taking place between the highly reactive polar groups of the PVC matrix and water molecules. This in turn led to the weakening of cohesion forces existing among the polymer owing to which an enhanced translocation of oxygen molecules took place through the polymeric channel. While in case of PVC/clay nanocomposites, the content of clay tends to play an imperative role in deciding the level of permeability [14]. With increasing amount of clay, a significant decline in the permeability of oxygen was observed for nanocomposites. At a concentration of 6 ph,r the permeability was found to be tremendously hampered; however, when an ultra-low concentration, viz. 2.5 phr of clay was used,

Fig. 3.10 a CO2/N2, CO2/CH4, and O2/N2 ideal selectivities of PVC nanocomposite membranes; b diffusion coefficient of varied gases in nanocomposite membranes (Reproduced with permissions from [13])

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Fig. 3.11 Oxygen permeability for the various PVC/1.31 PS nanocomposites as a function of clay content (Reproduced with permissions from [14])

the permeability was left unaffected. This decline in the level of permeability can be illustrated on the basis of the presence of platelets. As in this case, the platelets were present in an insignificant amount, hence providing the least resistance to permeability and diminished requirement of tortuous path [14]. (x) Synchrotron techniques (a) Small angle X-ray scattering Small angle X-ray scattering (SAXS) often called as non-crystalline diffraction (NCD) is a well-established analytical characterization technique for microstructure examinations in different materials. The information about structural inhomogeneities is probed on the basis of the difference in the electron density. This technique measures the scattered X-ray force as a function of typically small scattering angles. SAXS is utilized to characterize the size of inhomogeneities (e.g., pores, incorporations, second-stage districts) in polymer blends and small-scale emulsions. SAXS provides fundamental data on the structure and elemental dynamics of large macro-sized congregations in low-ordered environments. SAXS provides an information on the specific composition and density fluctuation of the sample specimen. These are the characteristics for numerous perplexing materials, for example, polymers and colloids. SAXS can cover an angular range of up to 1° and can characterize particles ranging between 1 and 1000 nm. Mathur and Sharma [15] performed the structural characterization of cadmium sulfide (CdS)-embedded polystyrene/polyvinylchloride (PS/PVC) nanocomposites (CdS-PS/PVCnc) using SAXS (Fig. 3.12). His study was primarily focused on envisaging whether the dispersion containing composites was lying within the nano-range or not. The SAXS analysis revealed that the CdS-PS/PVCnc portrayed a higher scattering intensity when contrasted with their counterparts without CdS-dispersed specimens. This was ascribed to the fact that the void sites in the respective polymer matrix were occupied by the CdS nano-fillers. These nano-fillers then acted as independent scattering centers and contributed comprehensively by enhancing the scattering intensity in the respective nanocomposites SAXS pattern [15].

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Fig. 3.12 SAXS patterns for PS, PVC, and PMMA along with their respective CdS nanocomposites (Reproduced with permissions from [15])

The SAXS characterization reports also suggested a Gaussian/uniform distribution of the CdS nano-fillers within the corona of the polymeric PVC matrix, thereby diminishing the chances of conglomeration. Further, SAXS analysis of CdS-PS/PVCnc established that all the respective specimens lie well within the nano-dimensions and retained their nanocomposite nature. The physical structure characterization of CdS nanoparticles embedded PVC polymer matrix individually utilizing small angle X-ray scattering study uncovers that the SAXS can light up the morphologies of particular polymer nanocomposites [15, 16]. (b) Wide angle X-ray scattering Wide angle X-ray scattering (WAXS) also known as wide angle X-ray diffraction (WAXD) is well-established analytical technique which has been employed for the facile invigilation of crystallinity of polymeric specimens. The information about structural inhomogeneities is probed on the basis of scattered Bragg peaks. This technique measures the scattered X-ray force as a function of the 2Ɵ angle. WAXS is synonymous to SAXS; however, the two analytical techniques are distinct from each other as the inter-distance between the detector and the sample holder is comparatively shorter in case of WAXS. Owing to this, the diffraction maxima is observed at a larger angle in case of WAXS and vice versa in SAXS. WAXS can cover an angular range between 5 and 60° and is potent enough to characterize particles falling in the range of few nm to micrometer (1–1000 nm). WAXS provides fundamental data on the chemical composition or phase composition, texture, crystal size, and presence of film stress.

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In an experiment, solution pathway was employed for the facile synthesis of polyvinylchloride single-walled carbon nanotubes (PVC-SWCNTs) by Vega et al. [7]. In their study, the spectral property which is of uttermost importance was investigated via utilizing WAXS technique (Fig. 3.13). Data accumulated from WAXS studies revealed that the degree of crystallinity and crystallite size had an inverse correlation with the concentration of SWCNTs. As the concentration of SWCNTs rose up, a demarcating drop in crystallite size and degree of crystallinity was portrayed [7]. In another study, Patil et al. [17] adopted melt intercalation methodology for the preparation of polyvinylchloride-calcium carbonate nanocomposites (PVC-CaCO3). The intrinsic structure, degree of intercalation and exfoliation of inorganic nano-filler in PVC-CaCO3 nanocomposites were invigilated using wide angle X-ray scattering technique (Fig. 3.14a, b). It was successfully concluded from the WAXS analysis that the nanocomposites were found to be in intercalated and flocculated phase, and the possibility for the presence of any exfoliation was over ruled. These results also highlighted that the PVC-CaCO3 nanocomposites were present in an inhomogeneous phase. This was ascribed to the formation of possible conglomerates due to high surface energy. Further, these results affirm that melt intercalation of nano-CaCO3 prompts phase separated systems [17]. The morphological taxonomy of the extruded layered silicate PVC nanocomposites was probed by Guzman et al. [18] using WAXS. The pattern obtained after WAXS analysis demonstrated that the PVC-bentonite-KZTPP nanocomposites were anisotropic in nature. Further, it was deciphered from the study that no scattering was present throughout the pattern, and most of the equatorial reflections were confined along the plane parallel to the molded at sheet’s plane, thereby suggesting a flow-induced preferred orientation of nano-plates, while

Fig. 3.13 WAXS spectra of pristine PVC and PVC-SWNTs composites (Reproduced with permissions from [7])

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Fig. 3.14 WAXD spectra of a PVC/ micro-CaCO3 composites; b PVC/nano-CaCO3 with 1, 3, and 5 wt% of filler (Reproduced with permissions from [17])

PVC-bentonite-Tamol-2001 nanocomposites remained in isotropic phase. Additionally, it was portrayed that the nanocomposites were devoid of scattering, hence indicating that the bentonite was impregnated as an exfoliate in the nano-plates [18].

3.4

Conclusion

In view of the information gathered by various researchers, we can reach the accompanying inferences; nano-fillers, blend of nano-fillers, and nano-fillers with a few polymers acquainted in PVC lattice lead with the development of PVC nanocomposites with better properties than those of pristine PVC. Some of such new additives acts as scavengers and managed huge postponement of PVC degradation temperature. Beside the thermal properties improvement, PVC nanocomposites postured better mechanical, rheological, photo stable, permeability, diffusion, and mechanical attributes depending upon the chosen nano-filler, blends of nano-fillers, blends of polymers and nano-fillers and the strategy utilized for their preparation. Final characterization of the nanocomposite will at least require a combination of techniques to completely address all physicochemical attributes. Not all the techniques discussed here are applicable to a wide range of nanocomposites. Likewise many of these techniques require some type of sample manipulation prior to analysis for example, drying or suspension in ultrapure liquids. This manipulation may bring about non-physiological states and perturbed properties. Hence, subsequent interpretation ought to be erred on the side of caution. The key issues to these technologies being fused into routine laboratory practice by analysts will be relative

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cost, ease of utilization, resolution ion capabilities, sample preparation requirements, simplicity of data interpretation, adaptability, bulk versus single molecule investigation, and so forth. Additionally, both the techniques and instruments depicted here are constantly developing to meet the requests of nanocomposite characterization, while bulk investigation will keep on playing a pivotal role; however, an additional focus should be placed on developing techniques capable of characterizing individual nanocomposite population. Such single-particle techniques do, however, need to guarantee enough discrete specimens are investigated to obtain statistically significant data that reflect the fundamental properties of the ensemble sample population. Critically, reasonable understanding of all results in the correct context ought to be another essential concern. In summary, large portions of the characterization techniques portrayed here will assume a pivotal role in the development of novel and, progressively complex nanocomposites and these, in turn, will be irreplaceable to the fate of nanotechnology. Acknowledgements Authors are thankful to DST, Government of India, for providing financial support. Rights and permissions. Appropriate rights license was acquired to reproduce the tables and figures. Further, the licensed contents reused in the chapter have been properly cited.

References 1. Hakkarainen M (2003) New PVC materials for medical applications the release profile of PVC/polycaprolactone-polycarbonate aged in aqueous environments. Polym Degrad Stab 80:451–458 2. Feldman D (2014) Poly (vinyl chloride) Nanocomposites. J Macromol Sci Part A Pure Appl Chem 51(8):659–667 3. Arya PK, Mathur V, Patidar D (2016) Thermo-mechanical performance of PVC/ZnO nanocomposites. Phase Transitions 1–8 4. Awad WH, Beyer G, Benderly D, Ijdo WL, Songtipya P, Gasco MMJ, Manias E, Wilkie CA (2009) Material properties of nanoclay PVC composites. Polymer 50:1857–1867 5. Xie XL, Liu QX, Li RKY, Zhou XP, Zhang QX, Yu ZZ, Mai YW (2004) Rheological and mechanical properties of PVC/CaCO3 nanocomposites prepared by in situ polymerization. Polymer 45:6665–6673 6. Madaleno L, Thomsen JS, Pinto JC (2010) Morphology, thermal and mechanical properties of PVC/MMT nanocomposites prepared by solution blending and solution blending + melt compounding. Compos Sci Technol 70:804–814 7. Chipara M, Cruz J, Vega ER (2012) Polyvinylchloride-single-walled carbon nanotube composites: thermal and spectroscopic properties. J Nanomater 8. Huang NH, Wang JQ (2009) A new route to prepare nanocomposites based on polyvinyl chloride and MgAl layered double hydroxide intercalated with laurylether phosphate. eXpress Polym Lett 3(9):595–604 9. Mondragón M, Valdes SS, Espíndola MES, López JER (2011) Morphology, mechanical properties, and thermal stability of rigid PVC/clay nanocomposites. Polym Eng Sci 51:641– 646

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10. Yalcin B, Cakmak M (2004) The role of plasticizer on the exfoliation and dispersion and fracture behavior of clay particles in PVC matrix: a comprehensive morphological study. Polymer 45:6623–6638 11. Gao J, Du Y, Dong C (2010) Rheological behavior and mechanical properties of PVC/ MAP-POSS nanocomposites. Polym Compos 31:1822–1827 12. Gao J, Du Y, Xing L (2011) Rheological behavior and mechanical properties of PVC/ V-POSS nanocomposites. Adv Mater Res 217–218:555–558 13. Mohagheghian M, Sadeghi M, Chenar MP, Naghsh M (2014) Gas separation properties of polyvinylchloride (PVC)-silica nanocomposite membrane. Korean J Chem Eng 31(11):2041– 2050 14. Sadek EM, Abd-El-Messieh SL, Khalil AA, Fatthallah NA, Eid AIA, El-Ashry KM, Motawie AM (2014) Some studies on Poly(vinyl chloride)/layered silicate nanocomposites: electrical, antibacterial and oxygen barrier properties. IOSR J Appl Chem (IOSR-JAC) 7 (11):37–45 15. Mathur V, Sharma K (2014) Probing nanoscale morphology of small angle X-ray scattering analysis of PS/CdS, PVC/CdS & PMMA/CdS. Polymeric Nanocomposites. e-J Surf Sci Nanotechnol 12:420–422 16. Mathur V, Sharma K (2014) Probing nanoscale morphology of PS/PMMA/CdS & PS/PVC/ CdS polymeric nanocomposites through small angle X-ray scattering analysis. Mod Instrum 3:25–28 17. Patil CB, Kapadi UR, Hundiwale DG, Mahulikar PP (2009) Preparation and characterization of poly (vinyl chloride) calcium carbonate nanocomposites via melt intercalation. J Mater Sci 44:3118–3124 18. Guzmán MER, Uribe AR, García EO, Olayo R, Ramos CAC (2008) Microstructure and dynamic mechanical analysis of extruded layered silicate PVC nanocomposites. Polym Adv Technol 19:1168–1176

Chapter 4

Applications of Polyvinylchloride (PVC)/ Thermoplastic Nano-, Microand Macroblends Elena Grosu

Abstract Polyvinylchloride (PVC) is one of the most applied polymers due to its mechanical and optical properties in a variety of industries, such as packaging, medical, food packaging, military applications, construction, as well as cable and wire manufacturing. The advantages of using PVC are based on its low cost and high versatility. Pure PVC is a rigid polymer. For this reason, to increase applicability, PVC must be compounded with several additives, mainly plasticizers like phthalates, such as dioctyl phthalate (DOP), ditridecyl phthalate (DTDP), dibutyl phthalate (DBP), addipates, citrates, to improve flexibility, as well as processing aids and stabilizers for melt processing and resistance to UV and other environmental factors of degradation. In recent years, due to the performance of nanomaterials and increasing demand of replacing wood, paper and metallic parts in several domains such as packaging, construction, military and aerospace applications, PVC has gained more attention and influence in the industry and trading. Several recipes of PVC were developed by including new additives such as inorganic and organic fillers at nano-, micro- and macro-dimensions, in order to improve and maximize biocompatibility, mechanical and optical properties together with decreasing costs. The most promising technology, nanotechnology, creates nanometer scale materials, with commercial and scientific relevance. Nanotechnology is present in top industries and has been explored for extending the product shelf life and offers quality, safety and stability of products. Nanoparticles in the PVC recipes lead to improved barrier and mechanical properties, and have gained good response from market and end users. Special attention for using nanoparticles in food packaging was increased; therefore, policies and regulation regarding health protection are being reviewed.




Keywords PVC blends Packaging applications Structural applications Recycling





Military applications


E. Grosu (&) The National Institute for Research & Development in Chemistry and Petrochemistry ICECHIM, 202 Splaiul lndependentei, Sector 6, Bucuresti, Romania © Springer Nature Switzerland AG 2022 V. P. M. and R. N. Darie-Nita (eds.), Polyvinylchloride-based Blends, Springer Series on Polymer and Composite Materials, https://doi.org/10.1007/978-3-030-78455-3_4

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4.1

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Introduction

Nowadays, PVC nano-, micro-, macroblends are designed to minimize negative effects of plasticizer migration and intend to be environmentally friendly. In this scope, bio-based plasticizers extracted from renewable resources and other fillers extracted from natural elements are present mostly in the PVC recipes. Rigid and flexible PVC nano-, micro- and macroblends with improved mechanical and physical properties attracted worldwide attention due to their industrial applications and academic interests. PVC is widely used due to its good processability, low flammability and low cost. The inconvenience is low thermal stability during melt processing that can be improved by adding stabilizers and other processing aids. Among other thermoplastic polymers, due to its versatile characteristics, PVC gained many domains of applicability, such as food packaging, military applications, coating industry, optical application, healthcare products, window frames and shutters in construction sector, industrial ware and toy factory. The final applications require PVC grades to accomplish requirements of clear or colored appearance, rigid or flexible, that can be achieved by optimal recipe of polymer, nano-, micro- and macroblends and their additives. Their processing technologies include injection molding, rotational molding, extrusion, blow extrusion, thermoforming, etc.

4.2 4.2.1

Applications of PVC/Thermoplastic Nanoblends Packaging Applications

Nanotechnology involves compounding thermoplastic polymers with some amounts (  10%) of specially treated nanoscale additives. Nanoparticles have the potential to improve polymer performances such as heat resistance, barrier properties, mechanical properties (strength, stiffness or dimensional stability) and flame retardancy. The presence of nanoparticles in the polymeric recipe does not increase the density neither reduce the light transmission properties. Types of nanofillers can be: calcium carbonate nanofillers, gold nanofillers, ceramic nanofillers, cellulose nanofillers, mica nanofillers, mineral nanofillers, phosphate nanofillers and zinc oxide nanofillers [1]. An increased attention was given to PVC nanoblends to be used in packaging applications. Some natural or synthetic inorganic nanofiller compounds have been added to PVC in order to improve their mechanical strength properties or to reduce cost. An increased attention was given to PVC nanoblends such as PVC/ montmorillonite [2, 3]. PVC nanoblends exhibit improved properties such as UV stability, stiffness or toughness depending of the nature of nanoparticles. In order to perform packaging

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applications, a method to prepare the nanoblend material by melt dispersion is needed. The nanoparticles are dispersed in the melted PVC. In the case of nanomaterial containing silicate clay such as montmorillonite, the shear forces during processing help the polymer to penetrate the clay and shear the clay sheets apart. Many studies have been performed to achieve a proper material that can be processed in packaging items. An interesting achievement [4] showed that the nanoblend material may contain PVC together with plasticizer such as phthalate or addipate characterized by absorbtion greater than 200 gkg−1 and the nanomaterial with particle size about 105 nm that can consist of montmorillonite, ammonium-treated montmorillonite, inorganic fibers (e.g., calcium carbonate or kaolin) in concentration 40–65% by weight [5], organic fibers (e.g., soybean flour, wood flour (hard and soft), nutshell hull and flour, natural fibers) [6], carbon and cellulose nanotubes and graphenes. In recent years, in response to consumer demands, researches in the field of biodegradable polymers and additives led to adopting innovative biodegradable packaging technology to improve quality and safety of active, intelligent and bioactive food packaging. The innovative packaging possesses enhanced food quality, safety, feasibility and bioactivity of functional components. Novel and innovative packaging techniques will allow the replacement of the traditional packaging with smart and active packaging to preserve food quality and safety, due to improved mechanical and barrier properties, and detecting pathogens [7]. In the present, are produced by nanotechnology and delivered many food packages based on PVC coated inside with aluminum nanolayer [8]. These packages have high performance physical-mechanical and barrier properties. Among different polymers such as polyethylene, polypropylene, polyvinyl acetate, polyvinyl alcohol, polyethylene terephthalate and polyamide, PVC can be used as the main polymer in nanoblends and offer good properties of melt processing in various desired shapes of food packaging [9]. Nanomaterials that can be blended with PVC to produce food packaging can be developed by different industrial methods such as microbial synthesis, biomass reactions, crystallization, solvent extraction/evaporation, self-assembly and layer-by-layer deposition [10]. A special attention is granted to the beverage packaging, where improving the strength, barrier properties, antimicrobial properties and stability to heat and cold can be achieved by nanoblend materials. The nanocomponents based on nanoclays to be used in the food packaging must have the dimension of about 1 nm, and their content in the blend may be less than 7% wt. Because of thermal instability of PVC, during melt processing it decomposes by the elimination of hydrogen chloride leading to formation of coloured conjugated polygenes. To prevent this difficulty, organically modified montmorillonite (OMMT) is used as nanoparticle material to accelerate dehydrohalogenation of PVC and enhancing discoloration. In the food packaging, nanoclays impede the diffusion of liquid or flavor components, and obstruct loss of carbon dioxide resulting in the impermeable barrier by which shelf life and quality are improved, and also the package is more strong, heat-resistant and lightweight.

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The development of novel, natural and synthetic nanomaterials which are antimicrobially active is significant and offers the potential of designing novel advanced materials and solutions to prevent microbial contamination and growth in food [11]. Many attempts have been made to include the antimicrobial nanoparticles based on silver nanoparticles (Ag NPs) in the bulk matrix of polymer during melt processing by reactive extrusion, injection, lamination or casting [9]. Stabilization of silver in the nanoparticles inserted by atomic layer deposition, electrochemical deposition and UV irradiation [12] enhances the bioavailability. Also, antimicrobial plasticizer based on complex of citrate-based silver was used within polymeric recipes [13]. Within nanoblends, PVC represents continuous or discontinuous phase [14] and the nanodimensional particles are discontinuous phase [15].

4.2.2

Structural Applications

Structural applications of PVC nanoblends are strongly influenced by the properties determined by filler particle sizes, geometric shape and surface quality or dispersion state. Nanofillers, for example, carbon black, become very attractive in modern electronic devices of submicron scales, to perform controlling the resistivity and permittivity [16–21]. Among several compounds, poly(methyl methacrylate) (PMMA)–PVC blends are used for solid electrolytes. Liew and Ramesh [22] have studied the effect of adding nano-sized filler dopant salt, lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), on the rheological properties of a blend electrolyte with ratio of 70 wt% of PMMA to 30 wt% of PVC. The purpose of improving rheological properties is to perform a solid polymer electrolyte (SPE) to be used in the electrical power generation and storage systems, with corrosive solvent leakage and harmful gas and high electrochemical and thermal stabilities, as well as low volatility [19, 20]. Other structural applications of the SPE can constitute chemical sensors, fuel cells, supercapacitors and analog memory devices [21].

4.2.3

Military Applications

Injection-molded plastic items performed from advanced materials are used increasingly to replace most of the heavy metal equipment in several military applications that offer a practical solution to be used by soldiers. There are many advantages of replacing metals with plastics in military applications such as: lower weight that increases safety and fabricating colored equipment by any color that eliminates the secondary painting or coating metallic parts.

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Compared with metal, plastic parts can be designed in complex shapes that eliminate electromagnetic radar/sonar and infrared heat source traces. Many polymeric materials are used in the military applications. Among these PVC nanoblends exhibit tough, flexible, flame retardant, transparence or opaque properties together with low cost. The main domains cover: • structures constructed from PVC nanoblends to shield detection equipment on military ships and aircraft, • military helicopters composed from PVC nanoblend foam blades to enhance spectral stealth capabilities (radar, infrared and acoustic), • coatings flexible from PVC nanoblends to be used on military vehicles to improve visual detection. PVC nanoblends in the recipes with improved characteristics for military application can be obtained by using inorganic fillers to increase electrical conductivity, improve resistance to heat or ultraviolet light, and reduce cost. Also, plasticizers in the PVC recipe decrease modulus and increase flexibility. Other additives can increase resistance to degradation due to ultraviolet light and heat or prevent oxidation. Inorganic nanoparticles such as glass fibers and carbon added into PVC recipes influence mechanical properties by increasing tensile and flexural modulus, improving toughness and stress/strain behavior. Using silica nanoparticles and plasticizer, polyethylene glycol (PEG) leads to performing intelligent body armor that is semi-viscous when equipment is not in active use, and hardens immediately upon impact. The most used additives in the PVC nanoblend recipes for military applications include: • nanoparticle mineral fillers to improve electrical properties and sound amortization, reduce cost and improve dimensional stability, • nanoparticle for the impact modifier to improve toughness, • glass fibers to improve stiffness properties and to increase heat resistance, • stainless steel fillers that improve conductivity and shielding, • lubricant fillers to improve wear and friction resistance properties, • flame retardants to increase burning resistance. The availability of multitude plastics and experienced complex extrusion and injection molders enable designers for military equipment and aircraft to diminish the limitations and to increase more developments in the future [22].

4.2.4

Aerospace Applications

Modern airplanes are not designed without plastic technical components, structural elements and propulsion components for interior. Together with some other plastics

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such as polycarbonate, PMMA and polyether ether ketone (PEEK), PVC nanoblends make the planes lighter, safer and more economical. The importance of technical plastics and composite parts in aerospace applications has grown rapidly. The applications of PVC nanoblends in aerospace consist in: interior components, technical parts, structural elements as well as components for navigation, propulsion engineering and satellite technology. The advantages of using PVC nanoblends in aerospace are the following: – – – – – – – – – – –

achieving lightweight constructions and hence fuel savings, the parts are fabricated economically, are approximately 50% lighter than aluminum, do not degrade by corrosion in comparison with the metals, flame resistance, low degree of thermal expansion, low level of degassing in vacuum, good electrical insulation, are best suited for use in dry operation under extreme conditions, properties of high performance, properties of high thermal and mechanical stability.

Before PVC nanoblends are approved for applications in aviation and aerospace, they normally have to undergo testing which is specific for the components and semifinished goods such as rods, sheets and tubes. The PVC nanoblends taylor designed materials are used in the production of special profiles for aviation and aerospace purposes and special tubes, solid profiles, hollow chamber profiles and particularly thin-walled profiles, safety through special fire protection properties satisfy the current flammability ratings. Industrial profiles with high-precision and preferred geometries for large volume production that satisfy the current flammability ratings for aviation and aerospace purposes can be produced. Designer and analysts of any metal to plastic conversion and experienced injection molders can modify the design to resolve continuous improvement and tight quality control, using mold-filling simulation, cooling simulation, predictive shrinkage and warping, and finite element analysis [23].

4.3 4.3.1

Applications of PVC/Thermoplastic Microblends Structural Applications

Increase in the world population led to the higher demand for affordable buildings. Building materials have industrialized due to improvements in technical knowledge [24] leading to expanding industry of building construction as one of the largest industries worldwide. The residential buildings are the highest share in general,

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followed by commercial institutions, public works and industrial constructions. New materials that must improve the environmental-friendly quality have adopted greater demand of plastic-based materials in the infrastructure field of construction industry. PVC microblends are well known because of their durability, aesthetics, ease of handling, high performance and superior corrosion resistance. These qualities together with high mechanical strength and low weight developed materials for bridge construction, including tough reinforcement rods and replacement decking as well as for strengthening and retrofit of deficient structures. Composite building materials based on PVC micro blends are conducting to innovations for speedy and high-quality construction to improve aesthetics and increase the speed of works [25].

4.3.2

Military Applications

Thermoplastic-based blends are widely used in military applications for various reasons. There are many applications of PVC microblends, especially in the cables and wires. Among these products in the domain of transport electricity and electric insulating, is distinguished some applicability of PVC/PMMA together with cobalt chloride (CoCl2) filler microblends. This polymeric system exhibits high ionic conductivity that leads to the potential application as electrolyte and as separator in solid-state batteries, to be used in military applications. PMMA has good chemical resistance and high optical transparency that allow this polymer to be used in special devices for electronic devices. But its properties of poor heat resistance, brittleness and stress cracking in numerous organic solvents limit its application. PMMA is used in wide applications in productive fields, and some technologies possess advantages of excellent optical properties, chemical inertness, good spectroscopic properties, thermal stability, electrical properties and easy forming and shaping [26, 27]. Although PVC has wide applications in several industries, this polymer has the disadvantage of poor thermal stability, low impact strength and high melt viscosity. For this reason, several modifications of PVC have been performed [28], together with modifications of plasticizers and elastomers [29, 30]. Compositions made on the basis of PVC preferably use CoCl2 as filler because of his attach on polymeric chains at both the amorphous or crystalline regions; also presents good dispersion through the disordered regions (amorphous regions) and generates charge transfer complexes or aggregates between the polymeric chains [31].

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4.3.3

Aerospace Applications

Aerospace plastic becomes a preferred solution for improving passenger comfort and creating an overall more economical flying experience. Within the aircraft, several plastics are greatly useful for insulators, wiring and sealing to bathroom mirrors and luggage compartments. The aerospace plastics for aircraft improve the flying to be more comfortable for passengers and more environmentally friendly. Plastics are used in aerospace and are used in almost every part of aircraft construction—even in military planes offering the advantages such as: – lightweight, – corrosion and other harsh condition resistant, – environmentally friendly, the use of aerospace plastics is making aircraft a “greener” travel option. The aircraft plastics can resist in some severe conditions: – – – –

many aerospace plastics have low flammability and are exposed to fire, radiation, high levels of steam and pressurized water lead to hydrolysis, extremely low temperatures.

PVC microblends have plenty of other applications that are increasingly benefitting from plastic as well. The nooks and crannies where aircraft PVC microblends can be found are as follows: – PVC/ABS microblends are highly suitable for interior wall panels and luggage compartments, and vacuum forming, so it can be manipulated into a wide variety of shapes, because of its heavy-duty strength and lightweight density. – PVC/PMMA microblends due to their resistance to thermal expansion are suitable for ventilation ducting and seals. In conditions of extreme temperatures, it is important that all of the plane's parts stay secured; for this reason, choosing plane plastics with a high degree of thermal stability will offer an aircraft added durability maintaining weighing. – PVC/PLA microblends exhibit morphology with interfacial layers with good bonding (Fig. 4.1) that improve impact strength and thermal stability; their applicability is luggage compartments and component parts of seats and dashboards. – Components of parts with technical application, such wiring, bushing, cams, rollers, and more: PVC/ethylene vinylacetate copolymer (EVA), or PVC/ polyethylene micro blends from wiring conduits to bushings and bearings, aircraft plastics can be found down to a plane’s smallest components, to maintain lightweight and contributes greatly to aircraft becoming a more economical form of travel. – Innovative designs that represent the future of aircraft: PVC/EVA copolymer microblends are used to design revolutionary airplane layouts from the point of view of ergonomic and aesthetical aspects; they are much easier to mold and shape than more traditional aircraft materials [33].

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Fig. 4.1 SEM micrograph of the PVC/PLA blend (Reproduced with permission from Elsevier [32])

Chlorinated polyvinylchloride (CPVC) possesses high corrosion resistance at elevated temperatures (higher than PVC). It is bendable, shapeable, weldable and fire-retardant [34]. Other aerospace applications of PVC/EVA copolymer are stock and custom plastic film and plastic sheet, in a soft, polished, flexible vinyl and a great alternative to other adhesive films. The films from this material stick without any adhesive and can be removed without leaving any residue. PVC microblend film is easy to process with and will not lose their shape, color or cling, for door coverings and protective masking. Depending on formulation, PVC microblends can be either rigid or flexible. Because vinyl softens easily, it is well suited for thermoforming, printing and box lid applications. But flexible PVC microblends are not suitable for outdoor applications, because they do not tolerate high temperatures or excessive exposure to UV light that can cause the material to be yellow, become brittle or turn hazy [35, 36].

4.3.4

Optical Applications

In order to produce parts with optical performance, some PVC/polystyrene (PS) microblends in different ratios were prepared by dissolving within tetrahydrofuran (THF) solvent and shacked. The films to be studied were achieved by casting method into Petri dish. UV–Vis spectrophotometer was used to measure transmittance T(k), absorbance A(k) and reflectance within range of (200–1100)nm. Starting from the values obtained that depends on the polymer type and component concentration within the blends, refractive index, dielectric constant and extinction

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coefficient were calculated, and their values exhibited dependence from wavelength and content of PS. It can be observed that extinction coefficient exhibits smaller values and decreases with increasing PS content. The parameters determined are absorption coefficients (a), the extinction coefficient (K) and refractive index (n) evaluated which exhibited good optical properties that are in accordance with increasing density and decreasing glass transition temperature Tg and melting temperature Tm [37–41]. Also, the optical and dielectric properties of prepared PVC/a-PMMA microblends were studied within applied field frequency. Interesting remark was that the applied frequency and the a-PMMA concentration have important effects on the physical parameters such as the optical energy gap, the glass transition temperature (Tg), the dielectric constant and the refractive index, conducted to demonstration of good optical properties [42].

4.4 4.4.1

Applications of PVC/Thermoplastic Macroblends Packaging Applications

Commercial applicability of PVC macroblends gained success as a packaging product due to their properties of strength, lightness, stability, impermeability and ease of sterilization. Type of plastic packaging for food does not affect the taste and quality of the foodstuff, while food keeps its natural taste protecting it from external contamination. To be used in packaging applications, PVC macroblends take into account synthesis of PVC by polymerization of the vinyl chloride monomer (VCM), in aqueous dispersion in the presence of a catalyst and a dispersing agent. In order to achieve vinyl chloride/vinyl acetate (VC/VA) copolymers, the most commonly used comonomer employed in copolymer manufacture is vinyl acetate monomer (VAM). The next step is compounding to obtain macroblends. Blending PVC with other thermoplastics as polyester leads to obtaining new materials with improved physical–mechanical properties such as abrasion resistance and tensile properties. Blends of PVC and polyester, or PVC with polyolefin rubber improve the heat stability and chemical resistance and rise temperature of use. Some of the packaging applications of PVC blends can enumerate bottles, transparent or blister packaging, punnets, cap sealing and rigid thermoformed foils [43]. For many general-purpose applications, a blend of the two in differing proportions is increasingly used. The foil for thermoforming can be produced by calendering or extrusion. The resulting foil is then fed in a thermoforming unit where it is heated and drawn into the mold, usually by vacuum. The thermoformed foil is used for packaging a wide range of food, biscuits and trifle portions. The great advantage of PVC in macroblends is its clarity, inertness and toughness [44, 45].

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85

Aerospace Applications

Progress achieved in the PVC macroblend industry determined the extendibility of their application area in the aerospace, particularly airplanes. PVC macro blends exhibit valuable characteristics, such as weight less than metal, corrosion resistance, easy to fabricate according to their prototypes designed in terms of color, texture and pattern. Due to lightweight characteristics, using PVC macroblend parts in the airplane construction decreases the aircraft weight which improves cost by reducing fuel consumption, in a way that for every 0.5 kg of airplane around 57,000 L of fuel per year can be saved. PVC macroblends are applicable to manufacture some inside and outside parts of aircrafts, such as: dashboard enclosures, radomes/nose cones, beverage carts, counter backsplashes, ceiling and wall panels and partitions, flooring, signage, video bezels, various seating parts, window reveals, shades and dust panes, components and box of sanitary kit, and equipment housings. Among several polymers used in aerospace construction such as: nylon, acrylic polymers, polyamide-imides (PAI), PEEK, polyethylenimine (PEI), phenolic/ thermosets, polyimide (PI), polycarbonate (PC), polyphenylene sulfide (PPS), polyphenylsulfone (PPSU), polytetrafluoroethylene (PTFE) and ultra-high-molecular-weight polyethylene (UHMWPE), one can mention PVC macroblends with acrylic polymers as PMMA. The benefits of PVC/PMMA macroblends are: • PVC–acrylic is a thermoformable, high-impact, fire-rated sheet for a variety of aerospace and industrial applications, • increased impact resistance, • fully preventing flame/smoke/toxicity compliant, • high resistance to chemicals, • easy to melt process in the shapes with uniform wall thickness, • multiple texture/color options. PVC–acrylic macroblends can be designed in a variety of grades, types, textures and colors, to replace metallic parts with certain forms offering integral metallic-colored upper and decorative layer. PVC–acrylic macroblend sheet offers a combination of several beneficial properties from both of its constituent materials: The PVC confers remarkable toughness and chemical resistance; the acrylic ensures impact strength, superior rigidity and formability. Application of PVC–acrylic macroblend products in the airplanes/helicopters must comply with all aircraft construction and travel-relevant regulations, including FAR flammability, heat release and smoke, and Boeing/airbus toxicity [46].

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Recycling and Lifetime Studies

Within a circular economy, PVC macroblends gained added value of the products, materials and resources that is kept as long as possible, as generating of waste is minimized. Innovation in designing and performing new compounds of PVC based on most modern and improved additives, especially inorganic and organic fillers, stays at the center of the entire value chain. As outlined by protecting environment laws, circular economy can be achieved in various ways, such as: lightweighting of products by reducing the quantity of materials required, increasing durability or the useful life of the products, efficiency by reducing the consumption of energy and materials within production process and use, substitution or reducing the use of substances or processes which create barriers for recycling [47]. PVC industry is well positioned within a true model of circular economy. The PVC blend products are fully and successfully recyclable leading to new opportunities of using in industrial sectors furthermore. PVC macroblend items are recycled mechanically through several innovative and more sophisticated mechanical and chemical recycling technology which allows to recycle difficult-to-treat PVC waste. It results in interesting new high-quality, virgin-like R-PVC compounds. PVC macroblends recycled can be used for a wide range of applications such as: pavements, packaging, garden and air hoses, geo-membranes, foils (roofing and flooring), mats, speed bump, shoe soles and footwears. In the present, important efforts are made for reducing progressively greenhouse gas (GHG) emissions along the entire production chain, by recycling PVC macroblends. The PVC macroblend value chain attains the attention in the research and development of new recipes to ensure maximum safety and protection of the environment and the health of users and consumers. The processing of PVC macroblends continued to adapt the products to legislation regarding protecting environment and to the evolving demands of the market. PVC alone or its macroblend compounds are attractive materials for the market [48].

4.5

Conclusions

The applications of PVC nano-, micro- and macroblends with several thermoplastic polymers and additives such as plasticizers, processing aid, stabilizers and inorganic/ organic fillers for the medical, biomedical, packaging, military and aerospace industries, as well as in structural elements in the building industry, are widely used. Numerous technical recipes of PVC were performed, improved and tested before

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their applications in packaging, major parts of airplanes/helicopters and of the structural components of building construction, also in optical devices and in many developed countries from all continents. The major number of micro-, nano- and macroblends of PVC contains mainly PMMA, PS, acrylonitrile butadiene styrene (ABS), EVA copolymer and other thermoplastic resins, together with plasticizers such as phthalates, addipates, citrates, nano-, micro- and macro-inorganic/organic fillers (e.g., calcium carbonate or kaolin) and organic fillers (e.g., soybean flour, wood flour (hard and soft), nutshell hull and flour, natural fibers) in concentration of 40–65% wt. These materials are to be used in packaging, medical field, construction and military applications because they can be applied in casseroles, medical devices, electronic devices, pipes, finishes, windows, doors, expansion joints and structural components. PVC nano-, micro- and macroblends are used in several industries because of their cost-effectiveness and lightweight. The level of satisfaction on the existing applications of PVC materials is promising good.

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Chapter 5

Factors Affecting the Properties of Polyvinylchloride (PVC) Nano-, Micro- and Macro-Blends Anca Andreea Ţurcanu

Abstract PVC is one of the most useful materials available to the plastic market, because of its properties like resistant, durable, lightweight, low cost, chemical resistant, but the inadequate disposal has contributed to strong non-economic issues due to the negative effects of chlorine on the environment. After PE and PP, PVC is the world’s third-most widely produced synthetic plastic polymers, and it comes in two forms: flexible and rigid. In both forms, PVC presents very good properties for a wide range of applications. Some of the most important and studied properties of PVC blends refer to mechanical properties, thermal stability and electrical properties, and it is very important to understand what factors affect these properties. Most properties are affected by factors like the nature of components used in the blend, compatibility between components, loadings of each component, crosslinking agent, exposure to radiation and others.




Keywords PVC Blends ties Thermal stability





Factors
Mechanical properties
Electrical proper-

Nomenclature 40 FEF AAc CB CKD CPE CS

40 phr fast extrusion furnace Acrylic acid Carbon black Cement kiln dust Chlorinated polyethylene Chitosan

A. A. Ţurcanu (&) Center for Research and Eco-Metallurgical Expertise, University Politehnica of Bucharest, 313 Spl. Independentei, 060042 Bucharest, Romania © Springer Nature Switzerland AG 2022 V. P. M. and R. N. Darie-Nita (eds.), Polyvinylchloride-based Blends, Springer Series on Polymer and Composite Materials, https://doi.org/10.1007/978-3-030-78455-3_5

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DBTM DEPH DOP DOTP EHA ENR ESbO ESO FEF HDDA HNTs KCP KI MBTS MFA MMA MPTS NR NRB PBN PE PEGDE PEO PMHS PP PU PVC PVCr SA SDB SDD SDH SDO TBLS THF TMPTA TMPTMA TMTD TPGDA XP-301 ZnO a-MSAN

Dibutyltin maleate Di-(2-ethylhexyl)phthalate Dioctyl phthalate Dioctyl terephthalate Ethylhexyl acrylate Epoxidized natural rubber Epoxidized soybean oil Epoxidized sunflower oil Fast extrusion furnace (FEF) carbon black-N550 Hexanediol diacrylate Halloysite nanotubes Kenaf core powder Potassium iodide Mercapto benzthiazyl disulphide Multifunctional acrylates Methyl methacrylate 3-mercaptopropyl trimethoxysilane Natural rubber Acrylonitrile butadiene rubber Phenylnaphthylamine Polyethylene Poly(ethylene glycol) diglycidyl ether Polyethylene oxide Polymethyl hydrogen siloxane Polypropylene Polyurethane Polyvinylchloride Recycled polyvinylchloride Stearic acid Isosorbide di-butyrate Isosorbide di-decanoate Isosorbide di-hexanoate Isosorbide di-octanoate Tribasic lead sulphate Tetrahydrofuran Trimethylolpropane triacrylate Trimethylol propane trimethacrylate Tetramethyl thiuram disulphide Tripropyleneglycol diacrylate Mixture of plumb salts Zinc oxide a-methylstyrene-acrylonitrile

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5.1

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Introduction

A continuous need for new materials is created by the increasing complexity of products that result from technological breakthrough and the desire to obtain improved materials for existing applications. The polymer blends area has had tremendous scientific and commercial progress during the past few decades, by realizing the efficiency of blending existing molecules rather than creating new molecules by the development of new chemistry [1]. The polymer blending process is made to improve the mechanical, thermal and physical properties, as well as the processing characteristics and cost reduction of the final product. In principle, blending two polymers together in order to achieve a balance of properties not achievable with a single one is an obvious and well-founded practice. The properties of the blends formed are largely dependent on the microstructure of the polymeric phases and hence their corresponding morphology [2]. After polyethylene and polypropylene, polyvinylchloride is the world’s third-most widely produced synthetic plastic polymer, and it comes in two forms: flexible and rigid. In both forms, PVC presents very good properties for a wide range of applications, and they are presented in Table 5.1. It is necessary to blend PVC with other polymers or copolymers to modify its properties. PVC blends consist of complex mixtures of PVC particles, lubricants, stabilizers, fillers and plasticizers created to give a wide range of end products with unique properties. The most important and studied properties of PVC blends refer to mechanical properties (tensile strength, Young’s modulus, elongation at break, etc.), thermal stability and electrical properties. The objective of this chapter is to see what factors affect the properties of PVC macro-, micro- and nano-blends.

Table 5.1 Properties of flexible and rigid PVC (adapted from Wikipedia [3]) Property

Flexible PVC

Rigid PVC

Density [g/cm3] Thermal conductivity [W/(m)] Yield strength [19]

1.1–1.35 0.14–0.17 1450–3600 psi (10.0– 24.8 Mpa) – – – –

1.3–1.45 0.14–0.28 4500–8700 psi (31– 60 Mpa) 490,000 psi (3.4 Gpa) 10,500 psi (72 Mpa) 9500 psi (66 Mpa) 5  10−15

Not recommended 1012 to 1015 1011 to 1012

65–100 1016 1013 to 1014

Young’s modulus Flexural strength (yield) Compression strength [psi] Coefficient of thermal expansion (linear) [mm/(mm °C)] Vicat B [°C] Resistivity [X m] Surface resistivity [X]

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5.2

Mechanical Properties

The mechanical properties (tensile strength, Young’s modulus, elongation at break, hardness) of PVC blends depends on the nature of the other components that go into the blends, amount of other components, curing method, and so in the next to come, the PVC blends are categorized and described as follows: • PVC/inorganic component (Al2O3, mica, Al, CaCO3, CB, graphite); • PVC/rubber (ENR, NBR); • PVC/other components (PEO, TPU, cellulose, starch, CS, HNTs).

5.2.1

Tensile Strength

The tensile strength refers to the stress needed by a blend sample to break. And it is expressed in Pascals or pounds per square inch. (psi) 1 MPa = 145 psi. Good tensile strength is needed by blends of polymers that are going to be stretched, for example fibres. 1. PVC/inorganic component blends Amount influence of mineral fillers like alumina oxide, mica, calcium carbonate used on PVC/(a-MSAN)/(CPE) blend was studied by Zhang et al. [4]. With the increase in mineral amount, the tensile strength decreases due to a low interfacial interaction between the polymer matrix and filler. This was also confirmed by Bishay et al. [5] who used alumina filler for PVC blends and found that the increase in alumina powder (wt. 0–40%) led to a decrease in elongation at break, due to the discontinuities in the structure of the PVC/Al blends. Jazi et al. [6] studied the effect of mass ratios of modified micro/nano-CaCO3 particles in PVC/surface-modified CaCO3 blends on the mechanical properties of the composites. The surface of the CaCO3 micro and nanoparticles was modified with PMHS and MPTS. They found that a mass ratio of 9:6 micro/nano-CaCO3 had a significant impact on the tensile strength of the PVC/surface-modified CaCO3 blend due to the increased interfacial interaction between the PVC matrix and the filler particles. 2. PVC/rubber blends: (PVC/elastomer and copolymer blends) One of the biggest disadvantages of unmodified PVC is that of being prone to brittleness, therefore it is necessary to formulate polymer blends with high impact resistance. To do so, the most used method is to disperse a rubber-based phase into the PVC, resulting in a high impact strength blend. Arayapranee et al. [7] studied the possibility of improving the mechanical properties of PVC blends by the combination of PVC with elastomers; therefore, they modified natural rubber by graft copolymerization with styrene and MMA using a batch emulsion

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polymerization process. The core-shell of the NR made it partially compatible with the PVC matrix and formed a blend with improved impact resistance and with a subsequent decrease in tensile strength. PVC/ENR blends are widely studied because of the high compatibility between components at any ratio [8] and also the good miscibility is believed to be given by the highly polar epoxide groups in the ENR molecules [9]. The compatibility of ENR25 and ENR50 with PVC was studied by Perera et al. [9], and they discovered that with a higher content in oxirane groups, the more miscible the PVC/ENR blend is, because with the increase in oxirane groups a stiffer polymeric plasticizer is obtained compared with other macromolecules with active pendant groups that plasticize PVC. In the case of PVC/ENR blends, the amount of kenaf core powder used as filler was studied [10] and also the effect of dynamic vulcanization on the properties of the blends. It was found that for the blends with dynamic vulcanization the tensile strength increases when compared to those without dynamic vulcanization, but with the increase in the amount of kenaf core powder, the tensile strength of the PVC/ ENR/kenaf blends decreases for both with or without dynamic vulcanization. This effect takes place due to the different polarity of the materials that form the blends, PVC/ENR matrix being hydrophobic while as for the kenaf powder which is hydrophilic, this gives the kenaf powder low wettability, leading to poor interfacial adhesion between the components and increasing the stress concentration area [11, 12]. Inside the blends, with the increase in kenaf powder, the stress concentration areas lead to micro-cracks that give the low tensile strength of the material. Ratman et al. [13] studied 50/50 PVC/ENR blends with different amounts of tribasic lead sulphate to see how the filler influenced the tensile strength of the blends, which were also irradiated using a 3.0 MeV electron accelerator with doses from 0 to 200 kGy. They found that a suitable amount of TBLS of 2 phr and a mixing time of 30 min gave the PVC/ENR/TBLS blend with the highest tensile strength, indicating a homogenous mixing. In another study, Ratnam et al. [14] investigated how the crosslinking agent and irradiation affect the mechanical properties of 70/30 PVC/ENR blends. As crosslinking agents, they used multifunctional acrylates: like EHA, HDDA and TMPTA, and found that with the increase in irradiation dose and the addition of MFA especially for TMPTA, all mechanical properties except for elongation at break were improved. The evolution of tensile strength is presented in Fig. 5.1. NBR–PVC being a miscible physical mixture of commercial importance is a vastly studied blend because both NBR and PVC are polar in nature and so they form compatible blends [15]. NBR acts as a permanent plasticizer for PVC and can be used in applications like food containers, wire and cable insulation and so on. The PVC improves chemical resistance and ageing of NBR in applications like conveyor belt covers, printing roll covers, feed hose covers, gaskets and so on, and PVC also improves tensile properties, the abrasion and tear resistance. The difficulty in forming successful PVC-NBR blends is the lack of suitable stabilizers for PVC which do not affect NBR.

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Fig. 5.1 Effect of radiation dose on the tensile strength properties for a PVC/ENB blend with different crosslinking agents (adapted from Ratnam et al. [14])

Some studies showed that other types of fillers lead to a decrease in tensile strength in PVC blends. For example, by using ESO combined with DEHP in PVC-NBR blends, a decrease in tensile strength can be observed with the increase in both DEHP and NBR amounts [16]. Another example is given by Ward et al. [17] who used graphite and copper nanoparticles as fillers and showed that with the increase in filler concentration the tensile strength values decrease. In the case of PVC-NBR with nano-clay blends, a volume amount of 2.5% nano-fillers like Cloisite 30B can considerably improve the tensile strength of the PVC-NBR matrix [18]. As showed by Abu-Abdeen and Elamer [19] in their work, the increase in PVC amount from 0 to 80 phr in PVC-NBR vulcanized with 40 phr carbon black nano-powder nano-blends leads to increase in tensile strength and also in elastic modulus, but the increase in PVC amount led to a decrease in abrasion resistance, elongation at break, the maximum degree of swelling and penetration rate. 3. PVC/other components Yazid et al. [20] studied the effect on the tensile strength of different amounts of PAni and naphthalene addition in conductive PEO/PVC/PAni blends. They found that with the increase in PAni loading the tensile strength of the blends tends to decrease due to the formation of a weak interface because of poor matrix filler adhesion, but they also observed that with the addition of naphthalene to the PEO/ PVC/PAni blends the tensile strength increased with an average of 10%. This might be caused by the presence in the structure of the blends of fused paired benzene rings from the naphthalene which leads to better mechanical strength. Ghani et al. also worked with PVC/PEO/PAni blends [21], and they also reported that with the increase in PAni loading, the tensile strength values tend to decrease. In their experiment, they increased the PAni loading from 0 to 30 (wt%)

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and found that at a 5 wt% PAni loading the tensile strength exhibits a maximum value due to the uniform distribution of the PAni in the PVC/PEO blends, but with increase in loading the blends become inhomogeneous and contribute to the diminishing of the tensile strength in PVC/PEO/PAni blends. In a different study, Ghani et al. [22] studied the effect of filler loading in PVC/ PEO/CB blends with and without PEGDE. They used CB in loadings from 0 to 30 wt% and found that up to 25 wt%. CB the tensile strength increases in both cases, with and without PEGDE, while at 30% it decreases. Similar results were reported by Yuan et al. [23], who found that with the increase in CB loading the tensile strength of the high-density polyethylene matrix also increases. When compared to the PVC/PEO/CB blends, the ones with PEGDE have lower tensile strength, because the addition of the PEGDE leads to a decrease in the stiffness of the blend caused by the replacement of interaction between the polymers with ones with the surface modifier. The effect of the amount of HNTs fillers in PVC/HNTs blends for ultra-filtration membranes also led to the increase in tensile strength, due to crosslinking between the components giving the material better elasticity and rigidity of the polymeric chains [24]. PVC plasticized with HEXAMOLL®DINCH was filled with micro-cellulose (150, 500 and 1000 lm) obtained from rice husk and the effect of filler amount on the tensile strength of the PVC micro-blend was studied by Crespo et al. [25], who showed that with the increase in filler amount the tensile strength values decrease due the weak interfacial interaction between the PVC matrix and the filler as result of poor adhesion. Also, the increase in plasticizer led to the decrease in tensile strength values because of high mobility in the polymer chains in the blends. In their work, Taurino et al. [26] showed that the increase in amount of chitosan used for the functionalization of PVC did not have a significant impact on the tensile strength of the PVC/CS blends, because of the activation of a stress transfer mechanism across the interface of PVC/CS blends, confirming the positive interaction between the components. Rosa et al. [27] studied how the amount of starch in mixtures of PVC plasticized with di(2-ethylhexyl) adipate affects the tensile strength of the blends. It was observed that with the increase in starch amount from 0 to 40 phr, the tensile strength decreases as does the elongation at break, because of the presence of functionalized groups of PVC lead to reactions with the hydroxyl groups from starch and form bonds among the components, thus obtaining a more rigid blend. 4. Curing method used on the PVC blends As showed by Hafezi et al. [28] in their work, which used two curing methods, the blends were cured by electron beam and sulphur method. The results showed that the blends cured with electron beam exhibit a 15% improvement in tensile strength compared with the blends that were cured with sulphur. The blends were then aged at 100 °C for 48 h and showed better hardness and tensile strength both before and after ageing in case of the PVC-NBR blends cured by electron beam compared to the ones cured by sulphur. This is explained by the higher crosslinking density and

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by the –C–C– bond existed in crosslinked PVC-NBR blends cured by electron beam. Ratnam et al. [29] showed that by using an electron beam irradiation dose between 0 and 200 kGy in a PVC/NBR blend with 4phr TMPTA led to a slight increase in tensile strength to a certain point at which the values start to decrease due to embrittlement that appears because of excessive crosslinking of material at higher irradiation doses.

5.2.2

Young’s Modulus

Young’s modulus is the ratio of stress to strain. It also is called the modulus of elasticity or the tensile modulus. Rigid materials, such as metals, have a high Young’s modulus. In general, fibres have high Young’s modulus values, elastomers have low values, and plastics lie somewhere in between. The stress–strain diagram is presented in Fig. 5.2. 1. PVC/inorganic component Jazi et al. [6] also observed in their studies that the mass ratios of modified micro/ nano-CaCO3 particles also affect Young’s modulus in PVC/surface-modified CaCO3 blends. They showed that at a lowering from 15:0 to 9:6 ratio in micro/ nano-CaCO3 particles gave an increase in Young’s modulus of the PVC/ surface-modified CaCO3 blends, while a further decrease of the mass ratio led to a decrease in the values of Young’s modulus. This is attributed to a restriction in the deformability of the PVC matrix due to the presence of the rigid filler. CaCO3 nanoparticles were mixed with PVC matrix, and the influence in the amount of filler on Young’s modulus was studied [30]. Young’s modulus of PVC/

Fig. 5.2 Stress–strain diagram

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CaCO3 nano-blends reaches optimal values with the increase of the loading of CaCO3 nanoparticles at 5 wt% and then decrease at 7.5 wt%. These results confirm that CaCO3 nanoparticles stiffen PVC. 2. PVC/NBR blends Cloisite 30B was used by Esmizadeh et al. [18] as a nano-filler for PVC/NBR blends, and the effect of loading (vol.%) of nano-filler on Young’s modulus was studied. They observed that at a very small loading of Cloisite 30B (1.5%, 2.5%, 3.5%), the values of Young’s modulus increase, with an 80% increase at 3.5% nano-filler. Because of the presence of alkylammonium cations in the nano-filler which lower the surface energy of natural montmorillonite, improving the wetting characteristic of nano-filler with polymer chains also have high chemical activity and induce some polarity to nano-clay structure, improving the interface interaction of nano-filler layers and polymeric matrix [31]. As showed by Abu-Abdeen and Elamer [19] in their work, the increase in PVC amount from 0 to 80 phr in PVC-NBR vulcanized with 40 phr carbon black nano-powder nano-blends leads to increase in elastic modulus (Young’s modulus), but the increase in PVC amount led to a decrease in abrasion resistance, elongation at break, the maximum degree of swelling and penetration rate. At values of 60 phr and greater, Young’s modulus increases because the incorporation of PVC into 40FEF/NBR vulcanizates increases the stiffness of the blend. 3. PVC/other components Yazid et al. [20] studied how the different amounts of polyaniline and naphthalene addition in conductive PVC/PEO/PAni blends affect Young’s modulus. As the PAni loading increases, an improvement in Young’s modulus can be observed due to restriction on chain movement that the PAni has in the conductive PVC/PEO/ PAni blends. And also, the addition of naphthalene led to an average of 14% increase in the tensile modulus compared to the conductive PVC/PEO/PAni blends without naphthalene because the presence of naphthalene in the blends causes a better interaction between matrix and filler. PVC/PEO/PAni blends were also studied by Ghani et al. [21]. In their case, they found that with the increase in PAni loading from 0 to 30 wt%. Young’s modulus decreases, possibly because of the excess amount of filler in blends, causing aggregates to form and brake the blend inhomogeneous. Similar results were reported by Thanpitcha et al. [32] upon introducing in excess of 50 wt% PAni in chitosan/PAni blends, and they became inhomogeneous, leading to a decrease in modulus of elasticity. In the second study [22], they used CB as filler in PVC/PEO/ CB blends with and without PEGDE. They showed that with the increase in CB loading up to 25 wt% the modulus increases in both cases but decreases at 30 wt%. CB loading. In the case of the blends with PEGDE, Young’s modulus has higher values than the ones without, because the addition of PEGDE to the blends has a softening effect, reduces brittleness and a higher elasticity, leading to better interfacial adhesion between the components.

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Another team [33] studied how using graphite filler in PVC/PEO blends affected the conductivity and mechanical properties of this blends. They found that with the addition of graphite to PVC/PEO blends, Young’s modulus values of PVC/PEO/ graphite decrease and keep this tendency as the graphite loading increases, because of the deformation effect of graphite on the molecular chains in the polymer blend leading to reduced mobility. The effect of micro-cellulose (150, 500 and 1000 lm) filler in PVC plasticized with HEXAMOLL®DINCH was studied by Crespo et al. [25] who found that with the increase in filler, the values of Young’s modulus also increase. They also showed that the smaller particle size of the filler (150 lm) led to an increase in the values of Young’s modulus because of better alignment and dispersion of particles within the PVC polymer matrix. PVC/ENR/KCP blends were prepared by Ismail et al. [10], and the effect of KCP loadings was studies in regard to Young’s modulus of the blends. Young’s modulus presents a slight increased with the increase of kenaf core powder loading. The stiffness of the blends increases with the incorporation of KCP into the PVC/ENR matrix. PVC/ENR/KCP blends with dynamic vulcanization present higher Young’s modulus values than the blends without dynamic vulcanization because of the crosslink density inside the blends that increases with dynamic vulcanization which enhances the stiffness of the blends. In another study, Ramadan et al. [34] combined PVC with DEHP plasticizer and studied how the increase in the amount of DEHP affected the mechanical properties of the PVC/DEHP blends. They found that with the increase in % of DEHP from 75 to 85%, Young’s modulus decreases, as to be expected because of the softening effect that DEHP has on PVC.

5.2.3

Elongation at Break

Elongation at break, also known as fracture strain or tensile elongation at break, is the ratio between increased length and initial length after breakage of the tested specimen at a controlled temperature. It is related to the ability of a plastic specimen to resist changes of shape without cracking. The elongation is calculated as the relative increase in length. Elongation = ɛ = (DL/L)  100 where »DL: final length» L: initial length elongation at break is measured in % (% of elongation vs. initial size when break occurs). Fibres have a low elongation to break, and elastomers have a high elongation to break. 1. PVC/inorganic component Zhang et al. [4] used different types of mineral fillers (mica, CaCO3 and Al2O3) with low-cost PVC/a-MSAN/CPE blends and found that with increase in filler

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amount the elongation at break tends to decrease because of a poor dispersion of the filler within the polymer matrix. This phenomenon is presented in Fig. 5.3. In another study, Bishay et al. [5] used alumina filler for PVC blends and found that the increase in alumina powder (wt. 0–40%) led to a decrease in elongation at break, due to the discontinuities in the structure of the blends. These discontinuities are formed by a weaker adhesion between the polymer matrix and filler caused by the larger amount of alumina in the structure. In their studies, Jazi et al. [6] reported that the mass ratio of micro/nano-CaCO3 also had a better impact on the elongation at break in PVC/surface-modified CaCO3 blends at 9:6 ratio between micro- and nano-CaCO3 particles as did for the tensile strength, Young’s modulus and impact strength. PVC/CaCO3 blends were studies by Guermazi et al. [35] and showed that with an increase in filler amount from 20 to 40% CaCO3 the elongation at break displays an obvious decrease. This can be attributed to a weaker interfacial adhesion between the polymer matrix and the filler because when the filler amount increases, the risk of formation of more aggregates is higher, which are failure initiation sites [36] and lead to more stress concentration around dispersed CaCO3 filler particles. 2. PVC/NBR blends In their work, Liu et al. [37] studied how the rubber content and matrix ligament thickness (T) affect the elongation at break of the blends. For PVC–NBR18 and PVC–NBR26 blends at T > 0,1 lm, the elongation at break is similar, for T = 0,1 lm the elongation at break for PVC–NBR18 blends increases to values that are significantly higher than those of PVC–NBR26 blends, while at T = 0,06 lm; the PVC–NBR26 blends present a sharp increase in the elongation at break. Basically, the elongation at break of PVC-NBR blends increases as T decreases. Ismail et al. [38] studied the effect of AAc on the mechanical properties, thermal stability, torque, stabilization torque, swelling behaviour, mechanical energy and morphological characteristics of PVCr/NBR blends. The blends were prepared by

Fig. 5.3 Effect of filler loading on the elongation at break of some PVC/a-MSAN/ CPE blends (adapted from Zhang et al. [4])

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melt mixing at a temperature of 150 °C and rotor speed of 50 rpm. It was found that PVCr/NBR + AAc blends exhibit an improvement in mechanical energy, stabilization torque, stress at peak and stress at 100% elongation, but lower elongation at break and swelling index than those of PVCr/NBR and PVCv/NBR blends due to increased compatibility of the incorporation of AAc in the blend. By using ESO combined with DEHP in PVC-NBR blends, an increase in elongation at break can be observed with the increase in both DEHP and NBR amounts, but with the increase of ESO amount in the ratio DEHP:ESO, the elongation at break starts to decrease [16]. The increase of the amount of PVC used in PVC 40FEF/NBR vulcanizates blends also influences the decrease in elongation at break values as shown by Abu-Abdeen and Elamer in their work [19]. This occurs due to the decreased deformability of rigid interphase between PVC and matrix material. Esmizadeh et al. [39] in their work prepared PVC-NBR nano-blends by melt mixing in a Brabender in which a self-crosslinking reaction occurs. The extent of crosslinking reaction increases with an increase in mixing parameters such as mixing and processing temperature and also on the rotor speed used. With the increase in crosslinking reaction, the elongation at break values of self-crosslinked samples are less than the values for uncrosslinked blends. 3. PVC/other components Yang et al. [40] studied how the alkyl chain length affected the elongation at break in PVC/isosorbide di-esters blends. SDH, SDD, SDO and SDB were the plasticizers used in the blends, and it was observed the carbonyl groups content and the molecular weight of the isosorbide di-ester used were the controlling factors on plasticizing PVC. The content of carbonyl groups decreases with alkyl chain length, and also its polarized interaction with PVC decreases, leading to poorer plasticizing efficiency. However, as the alkyl chain length increases, the molecular weight also increases, leading to the improved thermal stability of PVC blend. Rosa et al. [27] studied how the amount of starch in mixtures of PVC plasticized with di(2-ethylhexyl) adipate affects the elongation at break of the blends. It was observed that with the increase in starch amount from 0 to 40 phr, the elongation at break decreases because of the presence of functionalized groups of PVC lead to reactions with the hydroxyl groups from starch and form bonds among the components thus obtaining a more rigid blend. 4. Curing method PVC-NBR blends cured by electron beam compared to the ones cured by sulphur method present an increase in elongation at break both of 30% before ageing and 23% after ageing at 100 °C for 48 h [28]. This is explained by the higher crosslinking density and by the –C–C– bond existed in crosslinked PVC-NBR blends cured by electron beam.

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El-Nemr et al. showed the opposite of Hafezi that PVC-NBR blends that are irradiated present a significant decrease in elongation at break with an increase in irradiation dose, due to the crosslinking that occurs during electron beam irradiation [41].

5.2.4

Hardness

Hardness is defined as a material’s resistance to permanent indentation. It is one of the most measured parameters and often reported on technical datasheets of plastics and rubbers. Hardness is dependent on ductility, elastic stiffness, plasticity, strain, strength, toughness, viscoelasticity and viscosity. Bishay et al. [5] studied the influence of aluminium content on the hardness of PVC/Al micro-blends and found that with an increase in Al content from 0 to 40 wt % the shore A hardness suffers a slight decrease, which is attributed to a weak interfacial adhesion between the polymer matrix and the aluminium filler [42].

5.3

Thermal Stability

PVC macro-, micro- and nano- blends must have improved thermal stability for the different applications that they can be used in. As did before, we present how the thermal stability of PVC macro-, micro- and nano- blends is influenced by the loading of components in the next categories: 1. PVC/inorganic component The filler used in the PVC blends can have a very good influence on the thermal stability of the materials. For example, in the study of Bishay et al. [5], the aluminium content was varied from 0 to 30 wt% in PVC/Al blends, and it can be seen that the thermal stability is enhanced compared to that of unfilled PVC. The presence of aluminium increases the temperature at which the blends start to decompose. The Al powder acts as a barrier and minimizes the permeability of the volatile products from the PVC blends degradation. 2. PVC/rubber blends Ismail et al. [38] studied the effect of AAc on the mechanical properties, thermal stability, torque, stabilization torque, swelling behaviour, mechanical energy and morphological characteristics of PVCr/NBR blends and found that the addition of AAc in the PVCr/NBR blends led to a decrease in thermal stability.

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3. PVC/other components Hezma et al. [43] studied how PU content affects the thermal stability of PVC/PU blends and found that with increase in PU content the Tm and Td of the blends increased when compared to the PVC/PU control sample (100/0) but were slightly lower than the Tm and Td of the PVC/PU control sample (0/100), thus proving a good miscibility between the components and an improvement on the thermal stability of the blends. Neiro et al. [44] investigated the miscibility of PVC with PEO, in PVC/PEO blends by viscometric, microscopic and thermal analyses. From the viscometric and thermal results, they found that the PVC/PEO blends were miscible. The polymer– polymer interaction parameters, which were determined by depression of the melting temperature, are negative and proved to be dependent on the PVC molecular weight. The miscibility of the PVC/PEO blends is a result of donor– acceptor interactions between oxygen atoms of the PEO as a donor species and chlorine atoms of PVC, as a weak acceptor species.

5.4

Electrical Properties

The electrical conductivity of PVC/Al composites was found to be in the order of 10−8 S cm−1, and this value recommends such composites to be used in electrostatic dissipation applications [5]. Hajar et al. [33] studied the effect of graphite loading on the electrical properties of PVC/PEO/graphite and found that with the increase in graphite content, the electrical conductivity of the blend had a significant increase, but this increase in filler loading led to the decrease of the tensile strength. Reddeppa et al. [45] studied how potassium iodide affects the electrical properties of PVC/PEO blends and observed that the electrical conductivity exhibited Arrhenius-type behaviour, with the activation energy decreasing with the increase in KI loading. It was found that the conductivity of the PVC/PEO blend and PVC/ PEO:KI (42.5:42.5:15) electrolyte samples at ambient temperature (303 K) was 3.09  10−6 S cm−1, respectively 3.66  10−4 S cm−1, which were greatly enhanced at 363 K to 8.23  10−4 for PVC/PEO blend and 1.30  10−2 S cm−1 for PVC/PEO:KI blend, respectively. The free K+ ion concentration and also increase in the amorphous phase were responsible for the conductivity improvement in the PVC/PEO: KI electrolyte system. Ghai et al. [21] studied the electrical conductivity of PVC/PEO/PAni blends as a function of the PAni loading and observed that the conductivity increases with increase in PAni loading in the PVC/PEO blends. The electrical conductivity showed good improvement from 10−7 to 10−2 S/m, with PAni loading at 30 wt%.

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Because of the high PAni loading, conducting paths were formed in the PVC/PEO blends which made it easier for the electrical charge to hop through the polymeric matrix. In polymeric blends filled with low concentrations of conducting particles, the distance is large between the particles or clusters, and the conductivity is limited to hop by the presence of the polymeric matrix. Table 5.2 presents information referring to the materials used, preparation methods of the blends.

Table 5.2 Preparation methods for PVC blends Nr. Crt

Blends

Preparation conditions

Refs.

1

PVC/a-MSAN/CPE

[4]

2

PVC/Al

3

PVC/(micro/nano)CaCO3

4

PVC/[NR-g-(St-coMMA)]

5

1:1 PVC/NB and PVC/ENR blends 1:0.5:0.5 PVC/ENR/ NBR

6

PVC/ENR/KCP

7

PVC/ENR/OPEFB

8

PVC/ENR

9

PVC/NBR PVC/ DEHP PVC/NBR/DEHP PVC/NBR/ (DEHP-ESO)

Melt compounding; mixing temp: 180 °C; mixing time: 10 min; plasticizer: DOP Melt mixing: mixing temp: 180 °C; mixing time 10 min; mixing speed: 30 rpm; plasticizer: DOP (30 wt%); heat stabilizer: DBTM (3 wt%); curing agent: SA (0.3 wt%) Tumble mixing; mixing temp: 170 °C; mixing time: 5 min; mixing speed: 60 rpm; curing agent: PMHS and MPTS Melt blending technique; mixing temperature: 165 °C; stabilizer: lead sulphate 2.5 phr; lubricant: polyethylene oxide Melt mixing; first step: premixing PVC + stabilizer mixing speed: 200 rpm; mixing time: 10 min; mixing temperature: 30 °C; second step: mixing PVC with elastomers; mixing speed: 50 rpm; mixing time: 8 min; mixing temperature: 150 °C Melt mixing blending; mixing temp: 140 °C; mixing time: 8 min and 11 min for samples with dynamic vulcanization; mixing speed: 50 rpm; plasticizer: DOP; stabilizer: Cd/Ba stearate; curing agents: SA, ZnO, S, TMTD, MBTS Melt blending; mixing temp: 150 °C; mixing time 20 min; mixing speed: 50 rpm crosslinking agent: TPGDA; stabilizer: TBLS Melt mixing; first step: premixing PVC with plasticizer 4 phr (TBLS) and crosslinking agent 4 phr (TMPTA, HDDA, EHA, EB4830); second step: mixing temperature 160 °C; mixing speed: 50 rpm Blends were processed into sheets; processing temp: 170 °C; roll speed: 10 m/min, friction ratio: 1.25; co plasticizer: DEHP-ESO; stabilizer: Ba/Cd/ Zn

[5]

[6]

[7]

[9]

[10]

[11]

[13]

[16]

(continued)

A. A. Ţurcanu

106 Table 5.2 (continued) Nr. Crt

Blends

Preparation conditions

Refs.

10

PVC/NBR/copper or graphite

11

PVC/NBR/Cloisite 30B

12

PVC/NBR/40FEF

13

PVC/PEO/PAni

14

PVC/HNTs

15

PVC/cellulose (rice husk)

16

PVC/CS

17

PVC/Starch

18 19

PVC/NBR PVC/NBR

20

PVC/nano-CaCO3

21

PVC/NBR/nano-clay

22

PVC/PEO/graphite

23

PVC/DEHP

24 25

PVC/CaCO3 PVC/NBR

Solution-casting method; solvent for PVC: THF; [17] solvent for NBR: chloroform; 1,3 and 5 wt% copper or graphite Melt mixing; mixing temp: 160 °C; mixing time: [18] 8.5 min; mixing speed: 50 rpm; curing agents: SA, ZnO, S, TMTD, MBTS Mixed according to ASTM D 3182, mixing time: [19] 30 min; plasticizer: DOP; curing agent: S, MBTS; activators: SA, ZnO, antioxidant PBN Solution-casting technique; solvent: THF; [21] plasticizer: DOPT (15 wt%); PVC/PEO: 50/50 wt %; PAni: 0–30 wt%; mixing time: 4 h; mixing speed: 400 rpm Non-solvent-induced phase separation (NIPS) [24] method; HNTs ratio: 1–3 wt%, added into DMAc (85 g, as solvent) dispersed by ultrasonication for 10 min; PVP as pore former); mixing temperature: room temperature; mixing time: 12 h Mixing method; mixing temperature: room [25] temperature; mixing time: 20 min; mixing speed: 60 rpm; plasticizer: HEXAMOLL®DINCH (40, 50, 60, 80 phr); stabilizer: Vistab H–675 2phr; filler: rice husk (20, 30, 40, 50, 60 wt%) Melt mixing; mixing temp: 150 °C; mixing time: [26] 10 min; mixing speed: 100 rpm Mechanical mixing; mixing temp: 80 °C; mixing [27] speed: 1500 rpm; plasticizer: DOA; thermal stabilizer: Ca/Zn stearates; ESbO; anti-fogging; lubricant Carbon black N330 filler, ZnO, SA [28] Melt mixing; mixing temp: 170 °C; mixing time: [29] 10 min; mixing speed: 50 rpm; TMPTA Melt mixing; mixing temp: 180 °C; mixing time: [30] 10 min; thermal stabilizer: XP-301; SA Melt mixing; mixing temp: 150 °C; mixing time: [31] 8 min; mixing speed: 50 rpm; plasticizer: DOP Solution-casting method; solvent: THF; plasticizer: [33] DOTP Mechanical mixing; mixing temp: 110 °C; mixing [34] time: 5 min; mixing speed: 700 rpm Melt mixing; mixing speed: 15 rpm [35] Melt mixing; mixing temp: 160°C; mixing time: [37, 6 min; 46] (continued)

5 Factors Affecting the Properties of Polyvinylchloride (PVC) …

107

Table 5.2 (continued) Nr. Crt

Blends

Preparation conditions

Refs.

26

PVC/NBR/CKD

[41]

27

PVC/PU

28

PVC/PEO: KI

29

PVC/NBR

Mechanical mixing; mixing temp: 25 °C; mixing time: 15 min; antioxidant: TMQ; SA, ZnO; curing agent: TMPTMA Casting method; solvent: THF; mixing temp: room temp; mixing time: 24 h Casting method; solvent: THF; mixing temp: room temp; mixing time: 12–15 h; (47.5/47.5/5; 45/45/ 10, 42.5/42.5/15) Melt mixing, mixing temperature: 160 °C; mixing time: 6 min; lubricator 0.4 phr; stabilizer: 3 phr; plasticizer: 5 phr. Compressed moulding at 160 °C to make 4-mm-thick plates

5.5

[43] [45]

[46]

Conclusions

The blending of PVC with different components leads to better materials with improved properties. Some of the most important factors that affect the properties (mechanical, thermal and electrical properties) of PVC blends are as follows: • nature of components; the blend components involve a variety of ranges including inorganic components, polyolefins and their copolymers, different types of elastomers methacrylates and acrylates and others. The incorporation of these components within PVC exhibits modified results which ultimately influences the end use properties of the blends; • compatibility between components; which is very important because a blend with low miscibility between components can lead to a decrease in property values; • loading of each component in the blends; depending on the nature of the components, with an increase in component loading can lead either to a decrease or increase in the PVC blend properties; • preparation method; it is very important to choose an appropriate preparation method, because the compatibility of the blends starts in the mixing process of the components, and with a better dispersion between components the blends will have increased properties; • crosslinking method. However, the modification of the various characteristics and morphology evolution cannot be achieved by blending PVC with a single kind of polymer or other component but the selection of the component for blending is highly oriented to the specific application area. So, more investigations ought to be made to select the role of individual polymers, different copolymers and compatibilizers to bring modification in different

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properties of PVC. The technology of blending to enhance the properties of PVC is, however, an ongoing continuous trend. In this context, it is worthy to mention that the process of forming blend composite with PVC offers an emerging idea for future scope of research and upgrade of PVC properties.

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Chapter 6

Interface Modification and Compatibilization of Polyvinylchloride (PVC) Nano-, Micro- and Macro-Blends Anca Andreea Ţurcanu

Abstract Interface is the most physical-chemical active zone for materials and processes. Analyzing, understanding, modeling and functionalization of polymer interface is a complex necessity to produce innovative, high performance (co) polymeric macro-, micro- and nano-materials, -blends, -composites, or alloys, for a multitude of applications. Optimized polymer blends offer special properties, but initially they are in most cases thermodynamically incompatible, immiscible and they exhibit multiphase structures depending on the viscosity ratio and composition. An effective, well-known approach to stabilize immiscible polymers is adding random copolymers and block copolymers, because the copolymers are absorbed at the interfaces, reducing the interfacial tension and the forces toward macrophase separation, thus improving the microstructure and mechanical properties of blends. Another effective approach in improving the interfacial adhesion between polymer phases is functionalization of polyolefins. This promotes the decrease of particle size of the dispersed phase because grafted copolymers form at the interface during melt-blending process, enhancing toughness and izod impact properties. Keywords PVC

6.1


Interface modification
Compatibilization
Blend

PVC and the Basic Principles on Compatibilization of Polymeric Blends

Polymer blending is an already established industrial route to produce more performant and cost-effective polymeric materials like macro-, micro-, and nanocomposites, polymeric hybrids, or polymeric alloys, able to satisfy diverse and complex application demands in many fields. A. A. Ţurcanu (&) Centre for Research and Eco-Metallurgical Expertise, University Politehnica of Bucharest, 313 Splaiul Independentei, 060042 Bucharest, Romania © Springer Nature Switzerland AG 2022 V. P. M. and R. N. Darie-Nita (eds.), Polyvinylchloride-based Blends, Springer Series on Polymer and Composite Materials, https://doi.org/10.1007/978-3-030-78455-3_6

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112

Mechanical, chemical, and electrical insulation properties of polyvinylchloride (PVC) made it the third industrially produced polymer worldwide. Still, the necessity to improve PVC drawbacks and to achieve superior properties/cost performances for particular materials and applications continuously drives research into many diverse directions, all experiments being concentrated on new interface modification and compatibilization techniques with extremely different matrices, from polymers, biopolymers, rubbers, natural fibers, to inorganic, metallic, or advanced carbonaceous materials like graphenes, nanorods, and carbon nanotubes [1–6].

6.1.1

Types of Polymeric Blends

The design, development, and performances enhancing of advanced polymer blends are strongly dependent on two major factors: the control of the interface/interphase and the control of the morphology. From these two factors derive the first two characterization criteria: depending on the interface particularities, the polymeric blends can be homogeneous, meaning that the components are miscible at a molecular level, or heterogeneous. For example, poly(styrene) (PS)-poly(phenylene oxide) and poly(styrene-acrylonitrile)-poly(methyl methacrylate) (PMMA) are miscible blends, whereas poly(propylene) (PP)-PS and PP-poly(ethylene) (PE) are immiscible blends [7]. Classified in respect to morphology, polymer blends can be macro-, micro-, or nanoblends, where the macro-, micro-, and nano-dimension refers to the secondary component, can be self-sustaining, stratified on a support, or multi-stratified, or they can be amorphous, crystalline, or semi-crystalline, if the shape and organization at molecular level is considered. Moreover, depending on the chemical type of the second component, polymer blends can be polymer alloys, organo-metallic, or inorganic-organic. These types of polymer blends can also be categorized as blends with a discrete phase structure (i.e. droplets or particles in matrix), or blends with a bi-continuous or co-continuous phase structure [1, 8, 9]. Particular morphologies include fibrillar, core-shell, brushes, and onion ring-like polymer blends [10–12]. Li and Favis classified the polymeric blends into three types [13]. Type 1 blends are described as immiscible but compatible, demonstrating strong interactions at the interface, low interfacial tension, and a stable threadlike dispersed phase even at low concentrations, a low percolation threshold, and a broad co-continuous region. Type 2 blends are immiscible and incompatible, have a high interfacial tension, and often show a droplet dispersed phase structure at lower compositions, attaining cocontinuity through droplet-droplet coalescence. The main features of the type 2 systems include a higher percolation threshold than type 1, a narrower cocontinuous region than type 1, and the dependence of dispersed phase size on composition. Type 3 systems are ternary compatibilized blends. Such systems attain cocontinuity through reduced droplet coalescence. These systems are characterized by a higher

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percolation threshold than type 2, a narrow cocontinuous region, and nondependence of the dispersed phase size with composition.

6.1.2

Miscibility of Polymers

The polymeric blends offer appealing properties, but in most cases, without using particular compatibilization approaches, their components are thermodynamically incompatible, immiscible, and exhibit multiphase structures depending on viscosity and composition. Generally, polymer blends present two types of phase morphologies: (a) sea-island structure where one phase is dispersed in the polymer matrix in the form of isolated nano/microfibers, nano/microparticles, platelets, nanotubes, nanorods, or droplets; (b) co-continuous structure, where both compounds are continuous, situation characteristic for dual blends [1]. It is very important for practical applications to understand and control the internal interfaces properties. An effective, well-known approach to stabilize immiscible polymers is adding random copolymers and block copolymers, because the copolymers are absorbed at the interfaces, reducing the interfacial tension and the forces toward macrophase separation [14], thus improving the microstructure and mechanical properties of final blends. Another effective approach in improving the interfacial adhesion between polymer phases is functionalization of polyolefins. This method promotes the decrease of particle size of the dispersed phase because grafted copolymers are forming at the interface during melt-blending process, enhancing toughness and izod impact properties [14].

6.1.3

Strategies for the Compatibilization of Polymeric Blends

Compatibilization of polymers is necessary to improve the contact between two or more low miscible polymers, or between a polymer and an inorganic or metallic dispersed phase, the final aim being to create a better material with at least one improved property, like mechanical resistance, thermal stability, chemical stability, flexibility, color, flame retardant, and electrical insulating properties [1, 15, 16]. The compatibilization methods can be divided into two categories [17]: 1. By addition of: (i) a small quantity of a third component that is miscible with both phases (cosolvent, e.g., Phenoxy); (ii) a small quantity of copolymer whose one part is miscible with one phase and another with another phase (e.g., 0.5 to 2 wt% of tapered block copolymer); (iii) a large amount of a core-shell, multi-purpose compatibilizer-cum-impact modifier. 2. By reactive compatibilization, which uses such strategies as: (i) trans-reactions; (ii) reactive formation of graft, block or lightly crosslinked copolymer;

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(iii) formation of ionically bonded structures; and (iv) mechano-chemical blending that may lead to chains’ breakage and recombination, thus generation of copolymers (even at liquid nitrogen temperature), etc. Additionally, S. Bruce Brown’s classification of the reactive compatibilization strategies includes the following transformations [17]: 1. 1a. 1b. 2. 2a. 2b. 2c. 2d. 3. 3a. 3b. 3c. 3d. 4. 4a. 4b. 4c. 4d. 5. 5a. 5b. 5c.

Redistribution or Trans-reactions—Block & Random Copolymers Reactive end-groups of polymer-1 (P-1) attack main chain of polymer-2 (P-2) Chain cleavage/recombination involving all polymers Graft Copolymer Formation—Graft Copolymers Direct reaction of end-group of P-1 with pendent groups of P-2 Reaction of end-group of P-1 with pendent group of P-2 in the presence of a condensing agent Reaction of end-group of P-1 with pendent group of P-2 in presence of a coupling agent (c) Reaction of pendent group of P-1 with main chain of P-2 in a degradative process Block Copolymer Formation—Block Copolymers Direct reaction of end-group of P-1 with end-group of P-2 Reaction of end-group of P-1 with end-group of P-2 in the presence of a condensing agent Reaction of end-group of P-1 with end-group of P-2 in the presence of a coupling agent (c) Reaction of end-group of P-1 with main chain of the P-2 in a degradative process Crosslinked Copolymer Formation Þ Crosslinked Structures Direct reaction of pendent functionality of P-1 with pendent functionality of P-2 Reaction between pendent functionalities of P-1 and P-2 in the presence of a condensing agent Main chain of P-1 reacts with main chain of P-2 in the presence of a radical initiator Reaction between pendent functionalities of P-1 and P-2 in presence of a coupling agent (c) Ionic Bond Formation Þ Block, Graft or Crosslinked Structures Ion-ion association mediated by metal cations as linking agents (c) Ion-neutral donor group association mediated by metal cations Ion-ion association mediated by interchain protonation of a basic polymer by an acidic polymer.

In conclusion, the morphology stabilization can be achieved either by chemical pathway, like recombination of free radicals, grafting of functional groups, crosslinking by electron beam irradiation, or physical means, like blending or controlled crystallization.

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Interface Modification of PVC Macro, Micro, and Nano Blends

Interface modification of polymers is a mechanical-physical-chemical process of realizing the compatibilization between two or more components in order to tailor the final material’s properties for extremely diverse practical applications like sensors, actuators, and electrodes [18–20], nano- and ultrafiltration membranes [21, 22], advanced building materials with improved photo-aging and flame retardant properties [23, 24], nanocomposites with antibacterial properties and other biocompatible materials with medical use [25–29], and even pyrotechnic signaling compositions [30, 31]. The interface between the polymer and the nano/micro/macrofiller, also defined as mesophase [32], is a complex area characterized by heterogeneity, imperfect bonding, high-stress gradients, voids, microcracks. In addition, the filler creates complex, hard-to-quantify covalent and/or non-covalent interactions with the polymer matrix and its functional groups, and hindrance the chains’ mobility. At the interface, there are developing stress centers due to the differences between the thermal expansion coefficients of the nano/micro/macrofillers and the continuous polymeric matrix due to the applied loads, due to contractions during hardening (in thermoreactive matrices) or crystallization (in some thermoplastic matrices). The interface can also act like a nucleation center, a preferential adsorption site, and as a reaction center for chemical reactions. Because the interface is the most stressed area in a composite material, it is necessary to lower these voltage concentrations even by placing a material with the intermediate elastic modulus between those of the batch material and the polymeric matrix, or by placing a ductile material in this place. In the first case, the idea is to reduce the ratio elasticity modules for either of the two neighboring components, and so to reduce the voltage concentrations that may occur due to module differences. This solution is called “module interface gradually”. In the latter case, the local deformation capacity of the region interfacing is improved so that the voltage induced by the differences of the mode is improved, at least in part [29].

6.2.1

Interface Particularities of PVC Blends

The modification of the boundaries to the polymer-solid separation limit is can achieve two main ways [33]: (a) treating the surface of the filler material using compounds non-polymerizable or polymerizable micro-molecules, respectively macromolecular compounds; (b) modifying the polymeric matrix by group grafting functional or copolymerization.

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Reiterating the need to treat the surface of the filler materials, it can be noted that modifying batching component allows low surface tension by fixation of molecules, especially chemosorbites, to the solid surface. In this way, it ensures a good dispersion of the particles in the polymer matrix. Into the after the coupling agent treatment process is bound to the surface filling material, ensuring good adhesion between and matrix, leading at the same time to the appearance of a morphological area distinct: the interface. So far, the most common method of improvement the adhesion to the interface is the treatment of the filler materials with various compatibilizing agents capable of reducing the surface energy of a solid particles. One of the main issues is the choice compatibilizing agents capable of providing chemical bonding both with the polymer matrix and with the surface of the filler materials [9, 32]. The separation surface between the coupling agent and the matrix polymeric can be considered as a diffused interface where phenomena occur of interpenetration due to diffusion of the polymer in the intermediate phase and migration of the coupling agent molecules within the polymeric matrix. This diffusion phenomenon is more pronounced for materials that react with each other to form copolymers. Diffusion is supposed to be bidirectional interface between the coupling agent layer and the polymer matrix is because the two phases contribute to the diffusion process in directions opposite, forming a transition layer of composition that varies gradually. Besides, this diffusion process at the interface also occurs an adsorption process of the coupling agent at the surface of the filler particles [32]. The outer mesophase, between the polymer matrix and the coupling agent, is a copolymer with properties that vary continuously by radially direction. This copolymer is a diffused border, which at elevated temperatures develops through progressive movements of the macromolecules of the two phases in opposite directions. In the case of internal mesophase, the situation is much simpler because one of the phases is an inert substance, and the diffusion process at the interface. Filling material-coupling agent is insignificant.

6.2.2

Physical Modification of PVC Blends

The problem of structure of superficial or boundary layers of polymers on the solid surface is one of the central issues in the theory of adsorption and adhesion of polymers. Previously it was determined that due to the interaction adsorption on the solid surface, the number of conformations is limited possible macromolecules on the surface, which change the fact the relaxation behavior of the polymer in the boundary layers and density wrapping it. It can be imagined that the density of the polymer in the boundary layers on the solid surface depends on the following variables: cohesion energy polymer, superficial solid energy of the solid body, and elasticity of the network of polymer. Depending on the ratio of these factors, property changes physical superficial layers at different surface distances will be different.

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A cause of this behavior is the aggregate nature of adsorption real systems. For these, it was demonstrated on the surface the adsorbent passes from the solution, in particular the macromolecule aggregates, which have already formed in solution in the field of small concentrations. According to the concentration of the solution, the number and size of the aggregates are changed, which actually determines the complex structure of the adsorption layer Deformation and breaking of composites are governed by deformations micro-mechanical interfaces of the polymer matrix-filler interface. The two basic deformational processes, cracking and shearing, are accompanied to detach the particles in the batch polymers. If interfacial adhesion is weakness, fading is the dominant process. In the case of strong interactions, the intrinsic characteristics of the matrix predominantly determine the occurrence processes of microdeformation. Any change in the adhesion of the interface also changes the location of the maximum surface tension of the particulate filler material where the cracking is initiated. It is obvious, however, that interface adhesion and interface properties play a crucial role in determining the properties of the composite. In the case of good adhesion between the array and reinforcement fiber, the effort the maximum that can be transmitted from the array to the fiber is equal to the limit of shear flow, rm, for plastic matrices and resistance to shearing of the die in the case of rigid ones. In case of poor adhesion the maximum transmissive voltage from the array to the fiber will be less than rm and equal to the adhesion resistance. From these considerations become obvious that, in the absence of full adhesion, even a very low voltage applied to the matrix will cause detachment of its on the surface of the fiber and the formation of voids and thus can no longer be transmitted efforts to fiber.

6.2.3

Chemical Modification of PVC Blends

Grafting reaction by reactive monomers [acrylic acid (AA), vinyl silane or maleic anhydride (MAH)] on the main chain of a polymer, in the presence of peroxide, could be achieved. When a graft copolymer possessing functional groups reacts with a polymer containing on the chain end –OH, –COOH, or –NH2 groups, the desired compatibilizer between two different polymers are produced, due to the in situ reaction that occurs under high temperature and shearing conditions. Thus, the compatibilizer produced by reactive compatibilization exhibits improvement in interfacial adhesion in blends than a common physical compatibilizer. In a study performed by Wang et al. [34], ethylene vinyl acetate (EVA) was grafted with maleic anhydride (MAH), EVA-g-MAH, to investigate the compatibilization effect it has on PVC/PA11 blends by determining the morphology, mechanical and thermal properties of the blends. From the mechanical studies it was observed that with an increase to 15 wt% of EVA-g-MAH concentration, the PVC/PA11 blends achieve maximum values for tensile modulus, tensile strength, elongation at break, and impact strength. Above 15 wt%, the EVA-g-MAH excess

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is immiscible with PA11, leading to a decrease in compatibilization and mechanical properties. The anhydride functionality of EVA-g-MAH reacts at the interface with the amine end of PA11 and forms in situ copolymers at the interface, which reduces the interfacial tension, promoting a better dispersion of the PVC and adhesion between phases. From the SEM analysis of PVC/PA11 with and without EVA-g-MAH compatibilizer, it was observed that in the case of samples without the presence of EVA-g-MAH, voids are present that are attributed to PVC phase, which is less uniformly dispersed in PA11 phase and has a bad interface adhesion. The addition of EVA-g-MAH leads to a uniform distribution, reduction of the PVC phase size, and improved interface interaction with the PA11 phase. A study of in situ compatibilization of PVC/PS (polystyrene) blends catalyzed by anhydrous aluminum chloride was done by Niu and Li [35] They investigated the structure of PVC/PS blends by means of FTIR and the properties by means of test of mechanical properties, SEM, and DSC analysis. Their results showed that by adding the appropriate amounts of PS, anhydrous aluminum chloride, and styrene (6%, 0.6%, and 9%, respectively), the interface adhesion of PVC/PS blends increased. Also, the mechanical properties like tensile strength and notched impact strength of PVC/PS blends were improved. It was shown that with the increase of PS content when AlCl3 is added the tensile strength of PVC/PS increases first and then decreases. This phenomenon may occur because with the increase of PS content, more compatibility agent (graft copolymer), is produced and increases the compatibility of PVC/PS. But with the further increase of PS content, the excessive PS makes the systems’ compatibility worse, leading to the decrease of mechanical properties of PVC/PS blends. The DSC curves of PVC, PS, and PVC/PS blends were investigated and it was found that the PVC/PS blends present a single Tg at 89 °C, which is between 83 °C of PVC and 106 °C of PS. This indicates the formation of a homogenous blend between the PVC and PS when AlCl3 is used. The compatibilization of PVC/PS blends was also studied by Caneba et al. [36] who used a PS-PMMA block copolymer system and found that an effective compatibilization occurs when compatibilizer content is 1–5 wt% in a 50/50 PVC/PS blend. Kim et al. [37] studied the compatibilization effect of random-block terpolymer poly(x-lauryllactam-random-e-caprolactam-block-e-caprolactone) on various PVC blends: PVC/PA12 (polyamide 12), PVC/PP (polypropylene), and PVC/EPDM (ethylene-propylene-diene rubber).

6.2.4

Physical-Chemical Modification of PVC Blends

Properly wetting the surface of the filler material is the necessary condition for obtaining a good polymer blend. Thermodynamically, wetting is determined as the ratio of free energies superficial fiber reinforcement and adhesive. Solid bodies are

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divided into two conventional groups: energy low surface and high surface energy, distinguishing between them by the wetting capacity. Surfaces with high surface energy are wetted by virtually all pure liquids, i.e. the contact angle for them is almost zero. Surfaces with low surface energy they are wetted by only a small number of liquids. From the first group, solid bodies are the inorganic fillers and the second group are part organic fillers and synthetic fibers. From the point of view of obtaining polymer blends with good physical and mechanical characteristics is necessary to ensure a good moistening. Surfaces with high surface energy have the ability to be wet well. Usually, they adsorb slightly different organic chemical combinations, after which a substance monolayer is formed on the surface organic with low surface energy. Such a surface behaves already similar to a surface with low surface energy. Low surface energy materials cause two problems: the need to determine the superficial tension for providing wetting by polymers and ensuring sufficient wetting of the solid surface. If the wetting does not take place, either go on the route of introduction of the surface-active substances into the polymer matrix, which lowers the surface tension of the polymer, or through the process special surface area of the filler material. There are, in particular, complex cases when filling material is introduced into a mixture of polymers, complicated processes occurring redistribution of the fractions in the material volume, and the separation boundary of phases. All of these effects result in the uneven resistance of the layers boundary and volume of the polymer matrix. In a number of cases, on the border the low-limit layers, of low strength, appear determined not only by the adsorption of superficial active fractions which form a low strength monolayer, but also other causes to the basis of these causes are both technological factors and physico-chemical factors. The weak limit layers are the causes of the destruction of the adhesion contact in the use of composite materials, low water resistance, etc.

6.2.5

Stimuli-Responsive Interfaces

There are some surfaces that show reversible changes in their surface morphology and/or surface composition are currently the focus of multiple research groups. This kind of interfaces can have priori contradictory properties, such as adhesive/ lubricant and hydrophilic/hydrophobic properties, depending on the exposure environment. The influence of temperature and pH has been extensively applied to adjust the surface patterns among the various environmental parameters that can be modified. pH-responsive polymers introduced in a polymer blend as a single component can lead to adaptive surfaces. Polyelectrolytes with variable loading are excellent candidates for producing stimuli-responsive surfaces among the different polymers that can be used for this purpose [38, 39]. Nanostructured adaptive polymer surfaces, for example, were obtained through the diffusion of an amphiphilic BCPs

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(block copolymers) to the interface. When blending a high-molecular-weight PS matrix with a diblock copolymer, polystyrene-b-poly(lglutamicacid) [40] or PS-b-PAA [41] the surface segregation occurred. After annealing, the environment and pH depending hydrophilicity and the chemical composition changed at polymer surfaces. Temperature and pH-responsive surfaces were also obtained using multiresponsive copolymers. To this end, Bousquet et al. prepared homopolymer/diblock copolymer blends [42], consisting of a PS matrix and either polystyrene-block-poly (N,N′-diethylaminoethylmethacrylate) (PS-b-PDEAEMA) or polystyrene-block-poly(N,N′-dimethylaminoethylmethacrylate) (PS-b-PDMAEMA). The migration of PDEAEMA or PDMAEMA blocks at the surface is favored by surface segregation in humid environments, leading to a later temperature ad pH response. Both PDEAEMA or PDMAEMA are capable to change from hydrophilic state to a collapsed hydrophobic state, leading to an increase of temperature above the LCST (Low Critical Solution Temperature). They can also change their charge depending on the environmental pH. Interestingly enough, nanostructured domains were generated when using BCPs capable of self-assembly at the polymer surface. Toluen or THF were used as solvents to obtain the micellar structures or “donut-like” morphologies.

6.3

Compatibilization of PVC Macro, Micro, and Nano Blends

Due to thermodynamic incompatibility, in most cases, in polymer blends interfaces occur between phases. Inorganic fillers and fibers for reinforcement have the superficial energy high, this leading to incapability of dispersing in the polymeric matrix. Achieving homogeneity is one of the main problems when blends with thermoplastics are made. A miscible polymer blend is defined as homogenous to the molecular level, having negative free energy of mixing. In these kinds of blends the dispersed phase size is approximatively 2–4 nm, therefore smaller than the macromolecular radius of gyration. A polymer alloy is defined as an immiscible, compatibilized polymer blend with interface and morphology modification. Compatibilization is the process of modifying the interfacial properties in an immiscible polymer blend, leading to a decrease of the interfacial tension coefficient, and the formation of the desired stabilized morphology. Hence, compatibilization is an important process that transforms a mixture of polymers into an alloy, whit desired performance characteristics. Compatibilization methods are divided into two categories:

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1. By addition of: • a small quantity of copolymer whose one part is miscible with one phase and another with another phase (e.g., 0.5–2 wt% of tapered block copolymer); • a small quantity of a third component that is miscible with both phases (cosolvent, e.g., Phenoxy); • a large amount of a core-shell, multi-purpose compatibilizer-cum-impact modifier. 2. By reactive compatibilization, which uses such strategies as: • mechano-chemical blending that may lead to chains’ breakage and recombination, thus generation of copolymers (even at liquid nitrogen temperature); • reactive formation of graft, block or lightly crosslinked copolymer; • formation of ionically bonded structures; • trans-reactions; etc.

6.3.1

Thermodynamics of PVC Blends

Maurer has theoretically determined the influence of the interface on behavior linear viscoelastic elastics of the glass beaded polymer by extension Van der Poel model, core shell, with an elastic interface. Conformable the elastic interface and the cracks leaving it are responsible for energy dissipation. Resistance and modulus of elasticity are also correlated with these interactions interface. In general, a composite material consists of two phases: a continuous phase and a dispersed phase. If adhesion to the interface between the polymer matrix and the filler material is null, the properties of the material will look a lot like those of the polymer with voids, because the filler contributes very little to the overall strength. Therefore, a good adhesion is desirable between the components of the blend, in order to strengthen its structure. With all these, an appreciated quality of polymer-based composite materials is the ability to withstand cracking and fatigue. A crack in the mass of an elastic solid, under the influence of some forces traction, is surrounded by a strong tension field. The radius the curvature of the crack face is smaller, the higher the stresses which causes crack propagation. If the crack propagating encounters its inclusion and local adhesion is good, crack propagation is stopped. Into certain circumstances, the adhesion between the filler material and the polymer must be good, but not very high, and adhesion is desirable optimal interface. Characterization of this optimal value is a problem that must take into account a multitude of factors: the modules elasticity and Poisson coefficients of the two phases, size and the geometry of the two phases, the rheological properties of the polymer, and its effects of aging [35]. The total surface energy of an adhesive is composed of energy the interactions inside the phase volume and the energy due to asymmetry field strength field. The

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first component is determined by the nature of molecules that interact, being proportionate to mechanical work necessary to separate the molecules. Total energy of interaction resulting from the intermolecular contact between a solid and a liquid encompasses the energy the attraction interactions in the volume of each phase and the energy of interaction governed by the symmetry gradient of the field of force in the interphase area [36, 37]. The first component is measured by the required mechanical work separating the adhesive molecule from its own volume. Second component is measured as the mechanical work that would be done for separating the molecules of the two phases, considering that their interaction is due only to field strength asymmetry at the separation surface. The interfacial layer resulting from the adhesive interaction is characterized by its own field of force and the total energy of interaction at solid-liquid contact, whose value may exceed cohesive energies specific of each of the elements of the system, or may have a value intermediate. The energy spectrum of an adhesive joint is shown schematically in [38]. The diagram, as presented, allows a comparison of the energies corresponding to the constituent elements of system. Resistance of the adhesive bond can be quantified in terms of superficial energy of the substrate and the adhesive, or in terms of electrodynamic and microscopic properties. This theory is easily applicable to the polymer matrix-filler matrix interface. It has been shown that the mechanical strength of the composite material can be calculated with precision knowing the superficial energies of the material filler and polymer matrices [38].

6.3.2

Physical Compatibilization

PVC is the third worldwide produced polymer, and hence the interest in the study of compatibilization techniques with other compounds in order to satisfy the very wide and growing palette of applications. Physical compatibilization refers to reducing the size of particles used as (nano/ micro/macro) filler, especially for thermoplastic polymers and physical modification of interface by increasing adhesion. By adding block copolymers and random copolymers an effective approach is found to stabilize immiscible polymers, because the copolymers are absorbed at the interfaces and reduce the interfacial tension and hence the driving force toward the macrophase separation.

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Reactive Polymer Synthesis

Unwanted cross-linking and polymer degradation reactions can be avoided by applying polymerization techniques such as atomic transfer radical polymerization [43] and reversible-addition fragmentation chain transfer. For instance, these polymerization techniques offer interesting new possibilities to obtain the polymer blends and, such as initiating polymerization on the hydroxyl groups on the surface of a clay sheet. The monomers used could be methyl methacrylate, styrene, or vinyl acetate [44]. Also, developments in catalyst technology enable production of an excellent controlled comonomer distribution and stereospecificity along the polymer backbone or chain end [45]. If chemical treatment of the matrix polymer blend or the filler needs to be avoided or the interaction between the components is insufficient, then a third component, such as a polymer compatibilizer [20], can be added to the composite. Compatibilizers are added particularly to polyolefin/nanoclay composites prepared by melt blending because the organo-modification of the clay is seldom sufficient to create a favorable interaction between polymer chains and the clay sheets [46]. The interfacial adhesion between the clay galleries and compatibilizer is influenced by the mass ratio of the compatibilizer to the clay the molecular weight and the compatibilizers molecular weight distribution, functionality, and its concentration. Modern coupling agents are silane derivatives and organic titanates, and they offer the most general destination. They improve the hydrophobicity, the adhesion between the matrix and the filler material, shielding the filler surfaces against microfluids, which can lead to cracking, reinstalling the interface layer, improving the dispersion conditions, and watering of the filler. There are different ways to add silanes to the matrix polymerization including: • dry blending at room temperature or at high temperatures, • dispersion in water or solvation in alcohols or other organic solvents. The most used coupling agent is silane but organic titans are becoming competitive reaching the same volume of production. The effectiveness of coupling agents was demonstrated by the fact that most manufacturers of dispersed fillers in the US are already delivering their products treated with one or more of these coupling agents. The effect that can be achieved by chemical surface modification of the filler is strongly dependent on its nature. A common feature of many types of such materials is the presence of the hydroxyl groups on the surface. The hydrophilic properties of the surfaces are also determined by the presence or absence of acidic groups which also allow treatment of the organic amine filler particles.

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6.4

Analytic Methods for the Study of Interface and Compatibilization of PVC Blends

There are many ways of investigating the interface modification and compatibilization of PVC blends, seeing how they are dependent on the structural, textural, and morphological properties of the blends, which can be determined by many analytical methods. • Chemical structure: The chemical structure of PVC blends, or any other polymer blends for that matter, is generally identified by Fourier transform infrared (FTIR) and solid-state spectroscopy. In a study by Asadinezhad et al. [47], for medical-grade PVC, a coating of polysaccharides was added to observe the surface characteristics and the extent of bacterial adhesion. Surface chemistry is the main factor that determines most of the polymer surface properties. It basically refers to the molecular structure and organization on the surface that is also a measure of the tendency of the substance to undergo surface reactions. The surface chemistry of the blends can be altered by physicochemical interactions. In this study, the research team used different polysaccharides such as chitosan and pectin for the coating of medical-grade PVC. A new absorption at 1630 cm−1 was shown in ATR-FTIR spectra, presented in Fig. 6.1, which refers to the C=C stretching vibration due to the dehydrochlorination phenomenon. From all the surface chemistry modification of the blends, it was concluded that all presented polysaccharides assemblies onto the surface. • Microstructure and morphology: Crystallization behaviors of the PVC blends are usually studied by differential scanning calorimetry (DSC). The morphology is usually determined by scanning electron microscope (SEM) for surface morphology and by transmission electron microscopy (TEM) for details about internal composition. The formation of co-crosslinked product at the PVC/PE interface was confirmed to be very important for the final product properties. Xu and his team [48] studied the influence of NBR (content of acrylonitrile 33.5–36.5 wt%) on the properties of PVC/LDPE blends and also the synergism with cross-liking agent. A 60/40 (w/w) PVC/LDPE blend was obtained by melt mixing at 155 °C. The well-mixed blend was pressed into sheets at 170 °C under 20 MPa for 15 min. From SEM analysis the team observed that in the binary PVC/LDPE blends the interface is clear and the domain size is large, thus revealing its poor phase dispersion and interfacial adhesion. For the PVC/LDPE/DCP blend the domains were also large but the interface was blurred, in comparison with the PVC/LDPE/NBR/ DCP blend, which presents smaller domains and an indistinct interface, revealing good synergism between the two agents. In conclusion, NBR can promote phase dispersion between PVC and LDPE and also the interfacial adhesion. The probability of DCP existing at the interface will increase and more co-crosslinked products will form.

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Fig. 6.1 ATR-FTIR spectra of samples 1–5 split over three wavenumber ranges [47]

Novel PVC/Silica–Lignin blends were synthesized and characterized by Klapiszewski et al. [49] by means of thermal analysis (TGA), morphology (optical microscopy and SEM), and mechanical properties. It is well-known that the structure of blended materials determines their properties, especially such structural

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factors like bonding strength on the interface between the dispersed phase and polymer matrix, shape of dispersed phase inclusions, and homogeneity of filler particle distribution in the polymer matrix. The SEM images of the PVC/silica-lignin sample, presented in Fig. 6.2 [49], with 7.5% filler content showed a layered structure characteristic for gelated PVC, where the individual particles of filler are visible. It is safe to assume from this analysis that good interfacial adhesion took place between the silica-lignin filler and PVC matrix. From the SEM analysis by Wang et al. [34] of PVC/PA11 with and without EVA-g-MAH compatibilizer, it was observed that in the case of samples without the presence of EVA-g-MAH, voids are present that are attributed to PVC phase, which is less uniformly dispersed in PA11 phase and has a bad interface adhesion. The addition of EVA-g-MAH leads to a uniform distribution, reduction of the PVC phase size, and improved interface interaction with the PA11 phase. • Mechanical properties: The primary reason for interface modification of PVC blends is to improve the mechanical performance, thus the mechanical properties are vastly studied to ensure this. One of the major musts of PVC blends is to enhance as much as possible the equilibrium between the strength/stiffness and the toughness. Thus, it is necessary to characterize the mechanical properties of PVC blends, properties like flexural strength, impact strength, tensile strength, hardness, fracture toughness, etc. The most extensively used method to determine the mechanical properties of the PVC blends is tensile test and the main parameters obtained are tensile strength, Young’s modulus, and elongation at break. Xu and his team [48] studied the influence of NBR on the properties of PVC/LDPE blends and also the synergism with cross-linking agent. A 60/40 (w/w) PVC/LDPE blend was obtained by melt mixing at 155 °C. The well-mixed blend was pressed into sheets at 170 °C under 20 MPa for 15 min. The 60/40 (w/w) PVC/LDPE blend presented poor mechanical properties, but they found that with addition of NBR to the blends the mechanical properties improve, especially tensile strength and elongation at break are improved. This not only

Fig. 6.2 SEM images of PVC/silica-lignin blends, with 7.5% filler content [49]

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proved that NBR promotes the phase dispersion but also that it enhances the interfacial adhesion in the PVC/LDPE blends. Although NBR acts as a compatibilizer in the PVC/LDPE blend and improves the mechanical properties, the contact area between components remains small due to the insufficient phase dispersion. With addition of dicumyl peroxide (DCP) together with NBR to the PVC/LDPE blend, the mechanical properties are dramatically improved and also good synergism is obtained. More co-crosslinked products will form, and this will induce the modification of interfacial adhesion. Thus, compatibilization and crosslinking are both exerted sufficiently. In a study done by Ghani et al. [50] studied PVC/PEO/CB blends with and without PEGDE and found that the modulus of elasticity is higher in the case of blends with PEGDE than in the blends without PEDGE. This is because with the incorporation of PEDGE on the surface of PVC/PEO/CB blends the interfacial adhesion between blend components is improved. Jin et al. [51] studied the compatibilizing effect of SAN25 has in PVC/ABS blends, where the matrix of ABS is SAN35, by investigating Notched Izod impact strength and Vicat softening temperature, which was determined according to ASTM D256 and D1525. They observed the impact strength of unmodified PVC/ ABS blend, and found that it had a negative deviation from the simple additive values of PVC and ABS (18.0 kg cm/cm notch), due to the incompatibility between PVC and SAN35. The next two blends had different amount of SAN35 replaced with SAN25 and an improvement in impact strength was observed, thus proving the compatibilizing effect that SAN25 has. Zhang et al. [52] studied how mica, calcium carbonate (CaCO3), and alumina oxide (Al2O3) modify poly (vinyl chloride) (PVC)/a-methylstyrene-acrylonitrile copolymer (a-MSAN)/chlorinated polyethylene (CPE) blends. To determine what mineral filler presents the best interfacial interaction, the PVC/aMSAN/CPE blends where characterized by determined the mechanical properties, glass transition temperature, heat distortion temperature (HDT), and thermal stability. Notched Izod impact strength was conducted at room temperature using an Izod impact tester, following ISO 180) Tensile and flexural properties were carried out in a universal testing machine with a specific testing speed of 5 mm/min and 2 mm/ min, respectively, according to ISO527 and ISO 868. They found that with increase in filler amount, the Notched Izod impact strength, the elongation at break,tensile, and flexural strength exhibit a decreasing trend because of poor dispersion of the filler within the polymer matrix. But between the mineral fillers used, mica presented the highest interfacial interaction, Al2O3 is in the middle and CaCO3 has the lowest interfacial interaction, even though they are surface-treated under the same conditions. Grafting reaction by reactive monomers [acrylic acid (AA), vinyl silane, or maleic anhydride (MAH)] on the main chain of a polymer, in the presence of peroxide, could be achieved. When a graft copolymer possessing functional groups reacts with a polymer containing on the chain end –OH, –COOH, or –NH2 groups, desired compatibilizer between two different polymers is produced, due to the in situ reaction that occurs under high temperature and shearing conditions. Thus,

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the compatibilizer produced by reactive compatibilization exhibits improvement in interfacial adhesion in blends than a common physical compatibilizer. In a study performed by Wang et al. [34], ethylene vinyl acetate (EVA) was grafted with maleic anhydride (MAH), EVA-g-MAH, to investigate the compatibilization effect it has on PVC/PA11 blends by determining the morphology, mechanical and thermal properties of the blends. From the mechanical studies it was observed that with increase to 15 wt% of EVA-g-MAH concentration, the PVC/PA11 blends achieve maximum values for tensile modulus, tensile strength, elongation at break, and impact strength. Above 15 wt%, the EVA-g-MAH excess is immiscible with PA11, leading to a decrease in compatibilization and mechanical properties. The anhydride functionality of EVA-g-MAH reacts at the interface with the amine end of PA11 and forms in situ copolymer at the interface, which reduces the interfacial tension, promoting a better dispersion of the PVC and adhesion between phases. A study of in situ compatibilization of PVC/PS (polystyrene) blends catalysed by anhydrous aluminum chloride was done by Niu and Li [35]. They investigated the structure of PVC/PS blends by means of FTIR and the properties by means of test of mechanical properties, SEM, and DSC analysis. Their results showed that by adding the appropriate amounts of PS, anhydrous aluminum chloride, and styrene (6%, 0.6%, and 9%, respectively), the interface adhesion of PVC/PS blends increased. Also, the mechanical properties like tensile strength and notched impact strength of PVC/PS blends were improved. It was shown that with the increase of PS content when AlCl3 is added the tensile strength of PVC/PS increases first and then decreases. This phenomenon may occur because with the increase of PS content, more compatibility agent (graft copolymer), is produced and increases the compatibility of PVC/PS. But with the further increase of PS content, the excessive PS makes the systems’ compatibility worse, leading to the decrease of mechanical properties of PVC/PS blends. The compatibilization of PVC/PS blends was also studied by Caneba et al. [36] who used a PS-PMMA block copolymer system and found that effective compatibilization occurs when compatibilizer content is 1–5 wt% in a 50/50 PVC/PS blend. • Hardness: Hardness refers to the properties of a material that is resistant to different types of shape changes when applying force. For many applications, it is an essential and an important mechanical parameter of materials. There are three main types of hardness: scratch hardness (fracture resistance or plastic deformation due to sharp object friction), indentation hardness (plastic deformation resistance due to sharp object impact), and rebound hardness (An object’s bounce height dropped on the material). • Fracture toughness: fracture toughness is a property that describes a crack-containing material’s ability to withstand fractures. It is also one of the most important material properties. A stress intensity factor parameter is used to determine the fracture toughness of most blended materials. When the stress intensity factor reaches a critical value (KIc) or fracture toughness, unstable

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fracture occurs. The fracture toughness can be measured using different methods, such as single-edge notch bend and indentation fracture toughness. • Friction and wear: Friction and wear are part of the tribology discipline. Friction is the force of two contact surfaces or the force of a medium acting on a moving object, and wear is the material erosion from a solid surface by contact with another solid. The friction and wear properties of polymer blends are influenced by the particle size, morphology, and concentration of the filler. • Thermal properties: Thermal properties refer to the material properties that change with temperature. They are studied by thermal analysis techniques, which include thermogravimetric analysis (TGA), DSC, thermo-mechanical analysis (TMA), differential thermal analysis (DTA), dielectric thermal analysis, dynamic mechanical analysis (DMA)/dynamic mechanical thermal analysis (DMTA), etc. TGA/DTA and DSC are known to be the two most commonly used methods for determining the thermal properties of polymer blends. The thermal stability, onset of degradation, and the percentage of filler included in the polymer matrix can be demonstrated by TGA. The thermal analysis of PVC/aMSAN/CPE blends with mineral fillers was studied by Zhang et al. [52] by means of DSC analysis and the pure PVC/aMSAN/CPE (70/30/15) blends exhibit a single Tg at 91 °C, corresponding with the Tg of PVC/ a-MSAN (70/30) component. With the addition of different mineral fillers, there was no major changes in the Tg of PVC/aMSAN/CPE blends, except for the blend with Mica50 filler where the Tg is lower, fact attributed to the DOP plasticizer used. This proves that with addition of mineral fillers the compatibility between PVC and a-MSAN does not change (otherwise low shift of Tg will be observed). The HDTs were determined on a Vicat/HDT equipment at a heating rate of 120 ° C/h, and flexural pressure of 1.80 MPa, following ISO 75-1. From the analyses, they concluded that the mineral fillers do not have a negative impact on the HDTs of the blends, again except for the blends with Mica50, these trends being in agreement with the DSC analysis. With further increase in filler content, the Tg and HDS values decrease, in fact due to the poor interfacial adhesion between the polymeric matrix and fillers, which becomes more obvious as more amount of fillers are used. The DSC curves of PVC, PS, and PVC/PS blends were investigated by Niu And Li [35] and it was found that the PVC/PS blends present a single Tg at 89 °C, which is between 83 °C of PVC and 106 °C of PS. This indicates the formation of a homogenous blend between the PVC and PS when AlCl3 is used. Eastwood and Dadmun [53] studied multiblock or blocky distributed chlorinated polyethylene (bCPEs) ability to strengthen PVC/POE interface in comparison to that of randomly distributed chlorinated polyethylene (rCPE), by means of asymmetric double cantilever beam, peel test experiments, XRD, DSC analysis. In addition, they evaluated the dependence of molecular weight and chlorine content of bCPE to see how these parameters influence the compatibilization process. They found that the bare samples of PVC/POE blends exhibit very weak interfaces, with interfacial fracture toughness of 1.8 J/m2. Much more stronger interfaces are given

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by the addition of chlorinated polyethylenes to the PVC/POE blends, by creating a trilayer. Effect of molecular weight on the ability of the bCPE to strengthen the PVC/ POE interface was studied and the results indicated that improvement in the interfacial adhesion between PVC and POE is more pronounced with bCPEs than with rCPE. The optimum bCPE composition was determined to be 20% chlorine, and the interfacial adhesion force increases with increasing molecular weight. By comparing the PVC/CPE/POE trilayer and POE/CPE bilayer data it was found that the POE/bCPE interfaces are essentially as strong as the compatibilized PVC/POE interfaces. This implies that the strength of compatibilized PVC/POE interfaces is governed by the POE/CPE interaction. The extent of the compatibility was evaluated by DSC and XRD analysis, and the studies performed on pure components and blend samples indicate the presence of co-crystallization. The DSC analysis of 50:50 POE/bCPE blends presented melting peaks between the melting peaks of the individual polymers. From this combination of data, it is suggested that the POE will co-crystallized with each of the bCPE, giving a possible mechanism for strengthening of PVC/POE interfaces with the blocky copolymers. In their study, Jin et al. [51] investigated the compatibilizing effect of SAN25 has in PVC/ABS blends, where the matrix of ABS is SAN35. In a 50/50(w/w) PVC/ ABS blend some of the SAN35 was replaced with SAN25, leading to improved mechanical properties and compatibilization between polymers. From the DSC analysis, it was showed that all blends present two Tg, attributed to the PVC-rich phase (Tg1) and the ABS-rich phase (Tg2). In the case of the blends where some of the SAN35 was replaced with SAN25, the Tg2, DCp1 and DCp1 values decreased while Tg1 value increased compared to the unmodified PVC/ABS blend, indicating that the mixed-phase at the interface between PVC and SAN is thickened by the compatibilizing effect that SAN25 has in the blends. • Flame-retardant properties: A fire retardant is used to make it harder for materials to ignite, by increasing the ignition temperature and slowing decomposition. It works by different methods like absorbing energy from the fire or preventing oxygen from reaching the fuel. Polymer nanocomposites are attractive for flame retardant applications and nanoscale silica particles are a new type of flame-retardant nanocomposites. Polymer nanocomposites are attractive for flame retardant applications and nanoscale silica particles are a new type of flame-retardant nanocomposites. • Optical properties: transparency and refractive index are the most important optical properties of a material. Transparency is the physical property that allows light to be transmitted through a material. It is important for many uses in polymer blend applications. The refractive index is the ratio of the light speed in the vacuum to the light speed in the medium. It is the main property of optical systems using refraction and can be measured using a refractometer.

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• Rheological properties: Rheology is the study of the material deformation and flow under the influence of stress. Rheological properties measurement is helpful in predicting the physical properties of polymer nanocomposites during and after treatment. • Electrical properties: The electrical properties of polymers include several electrical properties commonly associated with dielectric properties and conductivity. When the fillers reach the nanoscale for several reasons, the electrical properties of nano-filled polymers are expected to differ. • Other characterization techniques: The distribution of the particle size of colloidal nanocomposites can be evaluated using two techniques: disk centrifuge photo- sedimentometry (DCP) and dynamic light dispersion (DLS). The first technique reports a weight-average diameter and the second reports an intensity-average diameter (Stokes–Einstein equation. Due to the different biases of these two techniques, DLS diameters are always expected to exceed the DCP diameters.

6.5

Conclusions

PVC interface modification and compatibilization can be achieved in many ways, some of the most effecting being given by: • physical modifications at the interface of the polymers in the PVC blends; • chemical modifications of the surface of polymer matrix and compatibilizer used; • a combination of the two; • stimuli-responsive interfaces. Good compatibilization in the PVC blends was observed when adding a small quantity of copolymer whose one part is miscible with one phase and another with another phase (e.g., 0.5–2 wt% of tapered block copolymer), but also when adding a small quantity of a third component that is miscible with both phases (cosolvent, e.g., Phenoxy); reactive formation of graft, block or lightly crosslinked copolymer also proved to be good compatibilizers in the PVC blends. The interface modification of the blends were studied by means of FTIR for surface chemistry, SEM and TEM for morphology studies, DSC and TGA to investigate the glass transition temperatures where one value was obtained in the PVC blends studied, thus proving the compatibilization effect.

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Chapter 7

Bio-Based Plasticizers for Polyvinylchloride (PVC) Maria Râpă, Raluca Nicoleta Darie-Nita, Ecaterina Matei, and Andra Mihaela Predescu

Abstract Polyvinylchloride (PVC) is a thermoplastic polymer widely used in large applications due to the excellent balance between cost and properties. Due to the environmental and human health concerns of consumption of petrochemical-based plasticizers, the use of bio-based plasticizers has been increasing. The new blends of PVC made with green plasticizers show attractive properties in terms of thermal stability, migration resistance, mechanical properties, etc. making them appropriate for the medical and industrial applications. This chapter reports the most recent and relevant studies concerning the synthesis and evaluation of bio-based plasticizers for PVC, with low toxicity and low migration levels.







Keywords Polyvinylchloride (PVC) DEHP Bio-based plasticizers resistance Mechanical properties Compatibility




7.1





Migration

Introduction

Polyvinylchloride (PVC) is a thermoplastic polymer showing low cost and excellent general properties [1]. PVC is one of the six most commonly used plastics (PE, PP, PS, PVC, PET, and PUR) accounted for 80.2% of the overall demand [2]. Global polyvinylchloride (PVC) market size was estimated at over 38 million tons in 2015 and is likely to reach more than 58 million tons by 2023, with CAGR gains

M. Râpă (&) Centre for Research and Eco—Metallurgical Expertise, University Politehnica of Bucharest, 313 Splaiul Independentei, 060042 Bucharest, Romania R. N. Darie-Nita Physical Chemistry of Polymers Department, Petru Poni Institute of Macromolecular Chemistry, 41A Gr. Ghica Voda Alley, Iasi, Romania E. Matei
A. M. Predescu Faculty of Material Sciences and Engineering, University Politehnica of Bucharest, 313 Splaiul Independentei, 060042 Bucharest, Romania © Springer Nature Switzerland AG 2022 V. P. M. and R. N. Darie-Nita (eds.), Polyvinylchloride-based Blends, Springer Series on Polymer and Composite Materials, https://doi.org/10.1007/978-3-030-78455-3_7

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of over 5%. Polyvinylchloride market revenue is anticipated to exceed USD 80 million by 2023 [https://www.gminsights.com/industry-analysis/synthetic-and-biopolyvinyl-chloride-pvc-market, Global Market Insights, 2018, Report ID: GMI321, last accessed 14.10.2018]. It is currently used in applications such as windows, tubes, pipes, etc. owing to flexibility, inherent flame retardation, and easy processing. It can be also used for manufacturing cables for electronics and electrical industry, automotive industry, healthcare, sports and packaging, etc. The neat polymer shows a high glass transition temperature and low thermal stability, which makes PVC to be rigid. The main disadvantages of this thermoplastic polymer are due to the dipole–dipole interactions of C(d+)–Cl(d−) bond. One way to remove these disadvantages is to add proper plasticizers, heat stabilizers, and lubricants during melt processing of PVC. These additives minimize changes in molecular weight by blocking the adverse effects of the tertiary and allylic chlorine atoms [3]. Thereby, the PVC products become flexible, with improved processability and decreased glass transition temperature (Tg), allowing their use in a variety of applications. The council of the IUPAC (International Union of Pure and Applied Chemistry) defined a plasticizer as “a substance or material incorporated in a material (usually a plastic or elastomer) to increase its flexibility, workability or distensibility” [4]. Over 95% of all of the medical PVC is used to manufacture bags for storage of blood and blood components, endotracheal tubes, catheters, drains, connectors used in hemodialysis, hemofiltration, auto-transfusion, surgery, anaesthesia, and intensive care [5]. The merits of PVC for use in medical applications are related to (i) flexibility; (ii) chemical stability and possibility of sterilization; (iii) low cost and availability; (iv) biocompatibility with the human body. The conventional petroleum-derived plasticizers used in many flexible PVC products are phthalate esters (also known as “phthalates”). The literature reported that phthalates represent more than 85% of world plasticizers production, of which 90% is annually used in PVC manufacturing [6]. They are used in amount of maxim 40% from the overall material. Among phthalate esters, di-(2-ethylhexyl) phthalate (DEHP) is the widely used plasticizer in order to give the necessary flexibility for PVC compounds from medical devices such as medical tubing and blood bags [7, 8], to footwear, electrical cables, packaging, and flooring. DEHP is low cost, processes well, and has provided good end-use performance. Approximately three billion kilograms DEHP are produced annually [9]. The main characteristics of DEHP are shown in Table 7.1. However, the application of DEHP as plasticizer was found to have adverse effects on the biocompatibility of the PVC materials used in medical devices as well on the surrounding environment. Concerns related to the potential hazards to environment and health associated with the release of DEHP from food packaging and medical devices made of PVC have been the subject of a very substantial amount of research. The European Food Directive 2002/72/EC has restricted the use of DEHP in food contact applications. This directive regulates the manufacture and distribution of plastic products intended to come in contact with food. Also, the Directive 2005/84/EC has limited the use of short-chained and low molecular weight phthalates such as bis

Bis(2-ethylhexyl) phthalate, (di-2-ethylhexyl phthalate, di-ethyl hexyl phthalate, dioctyl phthalate (DOP)

Sinonime for DEHP

Table 7.1 Characteristics of di-ethyl-hexyl phtalate Structural formula (C6H4(C8H17COO)2

Chemical formula

390.56

Molecular mass, g/mol

117-81-7

CAS

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(2-ethylhexyl) phthalate (DEHP), di-butyl phthalate (DBP), and benzyl butyl phthalate (BBP), as substance or as constituents of preparations, at concentrations of greater than 0.1% by mass of the plasticized material and banned their use in toys and childcare articles, and di-isononyl phthalate (DINP), di-isodecyl phthalate (DIDP) and dioctyl phthalate (DNOP) at concentrations of greater than 0.1% by mass of the plasticized material in toys and childcare articles which can be placed in the mouth by children. The European Directive 2007/47/EC stated that medical devices containing phthalates classified as Carcinogenic, Mutagenic, and Toxic for Reproduction (CMR 1a or 1b) must be clearly labeled as devices containing phthalates. DEHP has a low vapor pressure, and the temperatures for processing PVC articles are often high, leading to release of plasticizers, raising concerns about health risks. DEHP and its metabolites are known to affect the fertility of male rodents, and therefore, it is presumed that this may affect human fertility, significantly increasing the potential biohazards of this toxicant [10]. The main problems associated to the leached of DEHP in the healthcare applications are related to the induction of an acute inflammatory reaction, increased polymer stiffness/brittleness, and an increased failure rate due to breakage when compared to other biomaterials [11]. Upon contact with blood, albumin followed by globulin is instantly absorbed on the polymer surface [12]. In addition, the transparency of the polymer decreases, making it unsuitable for medical applications. There are studies related to the exposure of patients, especially those requiring extensive infusions, e.g. newborns in intensive care nursery settings, haemophiliacs, and kidney dialysis patients of DEHP. The detrimental dose for humans has been estimated at 69 mg/kg per day whereas the average daily exposure to DEHP is much lower (2.3–2.8 mg/kg in Europe and 4 mg/kg in the USA). The leachability of DEHP from PVC hemodialysis tubing was examined during maintenance hemodialysis of 10 patients with chronic renal failure [13, 14]. It was found that from an average DEHP quantity of 123 mg extracted from tubing during a single dialysis session, approximately 27 mg was retained in the patient’s body. In other study, it was found a leaching of di(2-ethylhexyl) phthalate (DEHP) and mono (2-ethylhexyl) phthalate (MEHP) from an irrigator and catheter containing DEHP (9.1–31.8%, w/w) as a plasticizer designed to enteral nutrition (EN) for neonatal patients at a level of 148 and 3.72 lg/(kg day) [15]. In vitro study conducted on intracellular calcium concentration (Ca2+)i, the di(2-ethylhexyl) phthalate (DEHP) stimulated both cell chemotaxis and reactive oxygen species production, contributing to inappropriate cell activation [16]. Nevertheless, the migration of DEHP is controversial issue. A Blue-ribbon panel examined the health effects of two commonly used plasticizers present in medical devices on hospitalized patients while receiving respiratory therapy or during haemodialysis [5]. The authors suggest that there was not enough evidence of harmful health effects to remove the plasticizers from use in medical tubing.

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In the last years, there have been several attempts to reduce the negative effects of plasticizers used for PVC products. The most effective approaches to reduce the leaching of plasticizers into physiological fluids are related to: (i) surface cross-linking, (ii) modification of hydrophilic/lipophilic surface, (iii) surface coating, and (iv) surface extraction. The surface modification of biomaterials is an economical and effective method by which biocompatibility and bio-functionality can be achieved while preserving the favorable bulk characteristics of the biomaterial, such as strength and inertness [17]. The control of surface properties is crucial in the design of biomaterials. Polyethylene glycol grafting on PVC surface by well-known Williamson reaction significantly improved the surface hydrophilicity compared with unmodified PVC [18]. Nevertheless, it is known that hydrophilic surfaces reduce bacterial adhesion [17]. In other paper, the flexible PVC tubes were coated with a, x-triethoxysilane terminated poly (ethylene oxide) (PEO-Si) [19]. In this way, it was shown that the leaching of di-ethyl hexyl phthalate was strongly reduced. The high silica content at the coating–extraction medium interface were evidenced by XPS analysis. Also, as a potential inhibitor for DEHP migration, poly(b-cyclodextrin-ester) network (b-CDP) via reaction of b-cyclodextrin with 3,3’,4,4’-benzophenone tetracarboxylic dianhydride was synthesized [20]. A stable hemocompatible coating was designed by consecutive alternating adsorption of iron (III) and heparin (Hep) and dextran sulphate (DS), onto PVC surfaces via electrostatic interaction [21]. Compared with the unmodified PVC surfaces, iron–polysaccharide multilayer coating presented a drastically reduced adhesion in vitro of platelets, polymorphonuclear neutrophil leukocytes (PMN), and peripheral blood mononuclear cells (PBMC). Another way to stop the DEHP leaching from PVC bags is to infuse miconazole solutions immediately after their preparation in PVC bags [22]. In addition, PVC materials containing DEHP represent a problem also from the perspective of environmental protection. They are slowly biodegraded in the environment, so it is impossible to be recycled and during combustion of the PVC waste, dioxin is produced. However, eco-friendly bioremediation of phthalates from medical devices has been large studied. Thereby, three mycelial fungi, Aspergillus parasiticus, Fusarium subglutinans and Penicillium funiculosum were found able to completely consumed intact DEHP physically bound to blood storage bags made from PVC [23]. These considerations together with the continuous interest among researchers to find alternatives to the petroleum plasticizers have been conducted to the investigation of bio-based plasticizers characterized by low toxicity, good mechanical properties, and biocompatibility with PVC.

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Recent Progress in Performance of PVC Plasticizers as Alternative to DEHP

7.2.1

Petroleum-Derived PVC Plasticizers

Many attempts have been made in the purpose to replace the DEHP with ecological plasticizers so that the new PVC compounds to have the same processability and similar technical properties as DEHP and present no health and environment risk. Manufacturers of flexible PVC articles can choose among several alternative plasticizers: other phthalates such as diisononyl phthalate (DINP), di-2 propyl heptyl phthalate (DPHP), diisodecyl phthalate (DIDP), and non-phthalates, e.g. 1,2-cyclohexane dicarboxylic acid diisononyl ester (DINCH), dioctyl terephthalate bis(2-ethylhexyl) benzene-1,4-dicarboxylate (DOTP/DEHT), and citrates. The main alternative petroleum-derived PVC plasticizers to DEHP are summarized in Table 7.2. The price of citrates is about three times higher than that of phthalates, and their application is limited to small-niche markets [24]. Other petroleum-derived plasticizers also include trimellitates and adipic polyesters, both typically used in high-temperature applications, tris(2-ethylhexyl) trimellitate (TOTM), etc. A method for the determination of TOTM released from PVC medical devices was investigated by liquid chromatography-tandem mass spectrometry (LC–MS/MS) [25]. An impressive amount of research work on alternative plasticizers to DEHP has been published; most of these studies have investigated the migration of the plasticizers, exudation, glass transition (Tg) evaluated by differential scanning calorimetry (DSC) or dynamic mechanical analyzer (DMA) analysis and mechanical properties (tensile stress, elongation at break and Young’s modulus, hardness), etc. Migration of DEHP, DINCH, DEHT and TOTM plasticizers from the PVC was studied into lipid emulsions [26]. The authors observed that, compared with DEHP, the TOTM migration was more than 100 times smaller, DEHT migration was 18 times smaller and DINCH migration was 8 times smaller, respectively. In other study performed by the exposure of 61 Norwegian participants to the phthalates and DINCH in air, dust, food, and hand wipes, during a 24 h period, it was concluded that, in general, the risk of phthalates to the human health remains low [27].

7.2.2

Green Plasticizers for PVC

7.2.2.1

External Plasticizers

Due to the depletion of petroleum resources and fluctuation of petroleum oil prices, renewable resources have received much attention over the past decade. PVC has been mixed with non-toxic plasticizers obtained from renewable resources to

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Table 7.2 The characteristics of some common plasticizers studied as alternatives to DEHP, as safe plasticizers Plasticizer name

Structural formula

Chemical formula

Molecular mass, g/mol

Diisononyl phthalate (DINP)

C26H42O4

418.62

Diisobutyl phthalate (DIBP)

C16H22O4

278.35

Dibutyl phthalate (DBP)

C16H22O4

278.35

Diisodecyl phthalate (DIDP)

C28H46O4

446.67

Di (2-ethyl- hexyl)terephthalate (DEHT)

C24H38O4

387

Butyryl-tri-n-hexyl-citrate (BTHC)

C28H50O8

514.7

Tris(2-ethylhexyl) trimellitate (TOTM)

C33H54O6

546.789

(continued)

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Table 7.2 (continued) Plasticizer name

Structural formula

Chemical formula

Molecular mass, g/mol

Acetyl-tri-n-butyl-citrate (ATBC)

C20H34O8

402.484

Di-isononyl-1,2-cyclohexane)di-carboxylate (hexamoll) (DINCH)

C26H48O4

424.67

Di-(2-ethylhexyl)-adipate (DEHA)

C22H42O4

370.57

prevent leaching of plasticizers, minimize deterioration of properties, and respond to environmental concerns. Natural–based PVC plasticizers increased over the last few years owing to the following advantages: 1. 2. 3. 4. 5. 6. 7.

Increase the workability Low toxicity Low migration Good compatibility with PVC Provided from renewable and biodegradable resources Increase the polymer chain flexibility Reduce greenhouse gas emissions.

The increased interest in the development of bio-based plasticizers for PVC is related to the plasticizers synthesized from biorenewable plant oils (for example, rice fatty acid [4], soybean oil [28], hydrogenated castor oil, camphor [29], etc.), agricultural by-products (for example, sugar cane [30], glucose [31], etc.) and waste (for example, cooking oil [32, 33]). Mechanical performance and properties of PVC/bio-based plasticizers are summarized in Table 7.3.

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Table 7.3 Mechanical performance and other properties of PVC/bio-based plasticizers blends Plasticizer

PVC blend formulation

Mechanical performance and other properties

References

Lactat derived plasticizer (ALCH) synthesized from L-lactic acid prepared by corn fermentation

PVC/ 1,4-cyclohexanedimethyl ester (ALCH)/ Thermal stabilizers 100 phr/60 phr/3phr The plasticized PVC films were obtained using a mechanical mixer, a double-roll mill, and a hot press

Migration tests performed at 30 ± 1 °C showed a reduction in cyclohexane (94.08%) and petroleum ether (84.66%) Migration rate of plasticized PVC film in difference food simulants showed a good migration resistance in distilled water and 3% (v/v) acetic acid (*0.8% and *0.9%, respectively) and poorer migration resistance in 50% (v/v) and 95% (v/v) ethanol (*6% and *23%, respectively) The mechanical tests showed: elongation at break 638.5 ± 6.5%; tensile strength 28.3 ± 0.3 MPa, Young’s modulus 4.4 ± 0.0 MPa and Shore A hardness 97.1 ± 1.0°ShA. The plasticizer made a stronger adhesion among the PVC chains The flexibility is improved (Tg 55 °C) attributed to the non-polar 1,4-cyclohexanedimethanol that can disrupt the interactions between PVC chains and create more free volume in the polymer

[30]

Aconitic esters (1,2,3-tri-carboxylic propylene) and tri-butyl aconitic acid (TBA) obtained from sugar cane

Rigid and soft PVC blends contain: plasticizer in quantities of 15 phr., 30 phr., and 40 phr., respectively, heat stabilizers, lubricants, and filler. They were processed in torque rheometer and the films were obtained by pressing

The authors found that the solubility parameters and dielectric constant of TBA plasticizer have the same values as those provided by PVC containing DINP plasticizer. This proved the compatibility of TBA plasticizer with PVC. Changes in Tg at 1 Hz as a result of PVC aging for 6 months at ambient temperature revealed an increase in Tg values by up to 20 °C. Tensile strength at break decreased with increase in plasticizer content, from 33 to 20 MPa. In the same way, Young’s modulus decreased from 455 to 12 MPa

[24]

(continued)

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Table 7.3 (continued) Plasticizer

PVC blend formulation

Mechanical performance and other properties

References

1’,7’,7’-trimethyldispiro-4,4″diyl) bis (methylene) dioctanoate (CDO) synthesized by reacting octanoyl chloride with camphorquinone diketal glycerol

Films containing up to 20 wt% plasticizer related to PVC were obtained by casting

The solubility parameter (d) of CDO (25.4 (J/cm3)1/2) is closed to that of PVC (21.2 (J/ cm3)1/2) proving a good compatibility With incorporation of plasticizer into PVC matrix, the Tg decreased from 85.3 °C (neat PVC) to 77.6 °C and 59.3 °C (in the PVC/CDO10 sample and PVC/CDO20 sample, respectively). The norbornene ring structure of CDO led to improve both tensile strength at break and flexibility of plasticized PVC. 10% CDO led to an increased tensile strength with 22% than neat PVC, while the elongation at break increased more than 32% compared with neat PVC 20% CDO led to a decreased tensile strength with 0.8% than neat PVC, while the elongation at break increased with 186% than neat PVC The PVC/CDO20 film showed a good migration resistance at a temperature of 25 ± 1 °C for 24 h to distilled water (0.8%), 10% ethanol (v/v) (0.3%) and 30% acetic acid (w/v) (0%)

[29]

Methyl 10(2-methoxy-2-oxoethansulfonyl) octadecanoate (MDA) and ethyl 10(2-ethoxy-2-oxoethanesulfonyl) octadecanoate (EDA) were synthesized from oleic acid and thioglycolic acid

100 g of PVC powder, 40 g plasticizer, and 2 g thermal stabilizer (Ca/Zn)

Increased thermal stability of PVC blends was explained due to two ester bonds, long fatty acid chain and sulfone group in structure of MDA and EDA Tg decreased toward 36.26 °C for EDA and 44.46 °C for MDA. Three polar groups had the ability to reduce the interaction between PVC chains MDA and EDA plasticizers reduced the tensile strength and tensile modulus and increased the elongation at break

[34]

(continued)

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Table 7.3 (continued) Plasticizer

PVC blend formulation

Mechanical performance and other properties

References

Shore A hardness recorded 88°ShA value for PVC/EDA compounds and 86°ShA for PVC/MDA compound. The prepared PVC films showed similar water migration than PVC/DEHP; Synthesized plasticizers are promising for food packing, children toys, and medical devices Natural polymeric plasticizer through polyesterification of rice fatty acid and polyols (octanol, diethylene glycol, and monopropylene glycol) in the presence of a catalyst

- 30 wt% plasticizer in relation to PVC - natural plasticizer modified with epichlorhydrine Films prepared by casting solution

Plasticized PVC showed a tensile strength at break *26 MPa and an elongation at break *104% Epoxidized plasticized PVC showed a tensile strength at break *22 MPa, an elongation at break *127% Plasticized PVC samples did not show any mass loss by evaluation at 40 °C for 48 h Low migration resistance by immersion into gasoline and petroleum ether was registered Tg was found to be: 65.8 °C for natural polymeric plasticizer and 62.5 °C for modified plasticizer

[4]

Linseed oil epoxy (LOE)

PVC/LOE films prepared by casting solution

Maximum stress of 33 MPa and 216% elongation at break were obtained by PVC/LOE blend (15/85 wt%). This blend showed the highest biodegradation (68%) by exposure 6 months in the soil burial test The potential applications could include packaging materials

[35]

Epoxidized linseed oil (ELO) and triethylene glycol ester of gum rosin (TEGR) as natural viscosity increasing agent

100 phr PVC and the adequate amounts of each additive, ELO, TEGR, or a mixture of ELO-TEGR, to reach 50 phr were mixed in a rotative mixer

Mixture of ELO and TEGR assured a good compatibility with PVC resin. Optimal ELO/TEGR blends to be used for the development of vinyl plastisols was found in the range of 80:20–60:40 PVC/ELO30-TEGR20 blend showed: Young’s modulus *1000 MPa, tensile strength at break 20 MPa,

[36]

(continued)

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Table 7.3 (continued) Plasticizer

PVC blend formulation

Mechanical performance and other properties

References

elongation at break *220% and hardness *50°ShD. The formulations were recommended for agricultural mulch films Epoxidized dicarboxylic acid dimethyl ester (epoxidized-C21-DAE) synthesized from tung oil

100 g of PVC powder, 40 g of plasticizer (epoxidized-C21-DAE), 2.4 g of CaSt2, and 0.6 g of ZnSt2 were compounded PVC films (*0.4 mm thick) were subsequently obtained

Thermal stability evaluated by discoloration test showed 290 min before epoxidixed-C21-DAE plasticizer beginning to become black. This result was in good agreement with thermal stability evaluated by TGA analysis The volatile mass performed at 70 °C ± 2 °C for 24 h showed 3.94% and it vas comparable with this property recorded by DOTP New synthesized plasticizer exhibited low exudation losses in distilled water and 50% (w/w) ethanol Tg value measured by DMA analysis showed 36.6 °C Tensile strength was 29.2 MPa and elongation at break was 308%. Long alkyl chain structures of epoxidized C21-DAE had a shielding effect and provided lubricity of PVC blend Exudation test was 0.08% and it was comparable to that of DOTP The epoxidized-C21-DAE plasticizer is introduced into polymeric matrix as both primary plasticizer and a high efficiency auxiliary thermal stabilizer for PVC

[37]

Epoxidized soybean oil (ESO) synthesized from waste cooking oils using citric acid

PVC films prepared with 25% ESO by casting solution

Tensile strength 25.3 ± 1.3 MPa was similar to a commercial wrap The film recorded the Tg value of 16.8 °C Plasticized PVC presented the same thermal stability like the

[33]

(continued)

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Table 7.3 (continued) Plasticizer

PVC blend formulation

Mechanical performance and other properties

References

commercial PVC wrap. The authors did that the addition of metallic salts or stearates to increase the thermal stability is not necessary Acetylated-fatty acid methyl ester-citric acid ester plasticizer (AC-FAME-CAE) was synthesized by using waste cooking oil and citric acid

PVC films containing up to 50 phr. plasticizer were obtained by casting solution

The films were immersed in 95% ethanol (v/v), at a temperature of 20 ± 2 °C for 96 h and showed 8% weight loss; in petroleum ether recorded 13% weight loss, while in distilled water only 1.5% weight loss was noted PVC films containing 50% AC-FAME-CAE showed a tensile strength at break 22 MPa; an elongation at break of 430% and a Young’s modulus 21 MPa AC-FAME-CAE with high molecular weight and polar structure (10 ester groups) showed a good miscibility with PVC, a reduced volatility (3%), and extraction loss. It was indicated to be used as auxiliary plasticizers

[32]

Isosorbide esters with different alkyl chain (R) length derived from glucose R = C3H7 (SDB); C5H11 (SDH); C7H15 (SDO); C9H19 (SDD)

100 phr. PVC/40 phr. plasticizer/4 phr. Calcium-zinc heat stabilizer films were prepared by solution casting

A large shift of the carbonyl group absorption band indicated good miscibility in the order: SDB˃SDH˃SDO˃SDD The plasticizers with increased alkyl chain length led to the decreased miscibility between the isosorbide diester and PVC Tg values, tensile modulus, and tensile strength increased and the hardness of PVC blends increased with the alkyl chain length while the elongation at break decreased

[38]

Three glucose hexanoate esters (GHs) synthesized at different

PVC/GH films were prepared by solution casting

IR spotlight technique displayed a good miscibility of all GHs plasticizers

[31]

(continued)

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Table 7.3 (continued) Plasticizer

PVC blend formulation

Mechanical performance and other properties

reaction times, produced by glucose

Blends with 20 wt% and 40 wt% GHs were prepared by solution casting

The studied films exhibited the following tensile properties: - Stress at break in the range of *17–35 MPa for 20 wt% GHs and *10–22 MPa for 40 wt% GHs - Strain at break in the range of *250–300% for 20 wt% GHs and *380–420% for 40 wt% GHs - E-modulus in the range of *780–1290 MPa for 20 wt% GHs and *180– 620 MPa for 40 wt% GHs

References

To demonstrate the advantages of using bio-based plasticizers for PVC, the results were compared with the data referring to conventional plasticizers. The presented data revealed that the introduction of bio-based plasticizers into PVC matrix led to lower stress and modulus, but the increased flexibility of PVC material, extending its application area. The degree of plasticizer migration depends on the compatibility of the plasticizers with PVC, the polarity and structure of the plasticizer, temperature, and the surrounding media, and other conditions. A good miscibility was found in the case of isosorbide esters with different alkyl chain length derived from glucose [38]. These plasticizers led to improved tensile properties, Shore A hardness and Tg. The authors attribute these improved properties to the dipole–dipole interactions between C =O and H–C–Cl bonds. PVC modified with bio-based plasticizers showed excellent thermal properties, as well as low values of exudation test, migration, and volatility. Low migration of PVC film was exhibited at the bio-based plasticizer modified with epichlorhydrin [4]. The links created between plasticizer with the epoxy groups of the epichlorohydrin improved the incorporation of plasticizer into the polymeric matrix. Other potential alternative plasticizers to DEHP could be monohexyl 2-methylsuccinate (MH2MS) and monohexyl 3-methylsuccinate (MH3MS) saturated diester compounds [39]. The authors tested the influence of succinate structure on biodegradation rate. It was found that the common soil bacterium Rhodococcus rhodocrous could rapidly break down all unsubstituted succinates, without the appearance of stable metabolites. Glass transition temperature (Tg) measurements showed the same reduction compared with Tg recorded by DEHP.

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The structure of some succinate and maleate diesters blended into poly (vinyl chloride) (PVC) and their side chains were studied regarding the plasticizing properties by Erythropel et al. [40]. The PVC blends were obtained with a conical intermeshing twin-screw extruder, at a rotation speed of the screws set to 60 rpm and the operating temperature in the range of 110–130 °C. Firstly, a master-batch containing 20 parts per hundred (phr) from each plasticizer, lubricant, and thermal stabilizer was compounded. Then, an additional 20 phr of the plasticizer was introduced into prepared master batch. This procedure assured no higher differences between nonplasticized PVC’s viscosity and that of used plasticizers. The authors concluded that an improvement in plasticizing effectiveness is obtained by increasing the length of the alcohol used in the esterification reaction, while a negative effect is obtained in the case of the increasing size of alkyl substituents added to the middle part of the succinate compounds. This was explained by the contribution of nonpolar groups (alkyl chains) to disrupt more PVC chain-chain interactions, allowing for more chain movement within the compound, and the improvement of flexibility. These PVC compounds showed lower Tg, stress at break, apparent modulus, and comparable strain at break than DEHP. Similarly, the improvement in plasticity by the long alkyl chain structures was met in the case of epoxidized dicarboxylic acid dimethyl ester synthesized from tung oil. This bio-based plasticizer showed a reduction in Tg value of PVC blend by 36.6 °C [37]. The authors explained this behavior due to the increase of free volume of the PVC amorphous region. Better mechanical results were obtained in the case of acetylated lactate ester bio-based plasticizer, in comparison with acetyl tributyl citrate commercial plasticizer [30]. These results were assigned to a large number of polar parts of lactic acid and carbonyl groups that assure a strong interaction with PVC chains, including the formation of hydrogen bonds between C=O and Cl–C–H.

7.2.2.2

PVC Plasticized with Two Bio-Based Plasticizers

In an attempt to replace the DOP from PVC, which cause changes in PVC properties and reduces the service life of materials, due to the loss of plasticizer with the extent of time, the combination of two plasticizers has been investigated. Recently, the effect of the cardanol acetate (CA), epoxidized cardanol acetate (ECA) in content of 30 phr and 50 phr, respectively, and the mixture between 50 phr cardanol-based plasticizers and 5% epoxidized soybean oil (ESBO) on the properties of PVC films prepared by solution casting was investigated [41]. Tensile properties and Tg of PVC-based bioplasticizers were plotted in Fig. 7.1. Cardanol is a renewable plasticizer to replace a traditional phthalate-based plasticizer, a by-product of cashew nut shell industry [42]. It is considered that the increased aromaticity in plasticizers improves their compatibility and reduces their volatility. The evidence showed that acetylation of cardanol hydroxyl group improves the compatibility with PVC. Epoxidized vegetable oils (ESBO) originating from soybean oil, is known as secondary plasticizer and a secondary

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Fig. 7.1 Mechanical properties and Tg of neat PVC and PVC compounds containing DOP, CA, ECA, or ESBO plasticizers (adapted from Lee et al. [41])

stabilizer in PVC. It showed limited compatibility with PVC and low plasticization efficiency, due to the unreacted double bonds and hydroxide groups formed during the epoxidation [37, 38]. The tensile strength at break of the PVC containing 30 phr CA and ECA, respectively, recorded higher values than those of PVC containing DOP (Fig. 7.1a). Incorporation of 5 phr ESBO to cardanol-based plasticizers led to improve the tensile strength at break and glass transition temperature for PVC/CA and PVC/ECA compounds. The authors explained that this behavior is attributed to the improved compatibility between ESBO and PVC, proved by Fourier transform infrared spectroscopy (FT-IR/ATR) and dynamic mechanical analysis (DMA). Furthermore, ECA was found to pass the leaching tests. In the case of plasticized PVC with cardanol acetate exposed to age at 105 °C for 5 weeks, a higher diffusivity of plasticizer together with low mechanical properties were observed [43]. The poor properties were explained by the lower molecular weight of cardanol acetate (*342 g/mol) and the low compatibility of the PVC-based cardanol acetate plasticizer.

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The synergetic effect of epoxidized soybean oil (ESBO) on hydrogenated castor oil plasticizer was demonstrated by investigating the plasticizer migration, tensile properties, and dynamic friction of plasticized PVC films [28]. The main application of these materials is for the wire and cable manufacturing industry.

7.2.2.3

Chemical Modification of PVC/Bio-Based Plasticizers

The bio-based plasticizers discussed above act as external plasticizers and they can leach from the PVC matrix because they are not covalently bonded to the polymer. In order to avoid the leaching of plasticizer with the increasing of time, the internal plasticizers have been developed. Internal plasticizers can be prepared via chemical modification of polymer matrix. For example, the azide-functionalized PVC (PVC-N3) was prepared by dissolving 2.0 g of PVC and 2.0 g of NaN3 in 100 mL of DMF (yield 95%) [1]. Then, propargyl ether bio-based triethyl citrate was added to PVC-N3 to obtain modified PVC (yield 92%). The plasticizing efficiency of the internal plasticizer showed a decrease of Tg to 35.7 °C compared with neat PVC that exhibit a Tg value of 87.6 °C. Lower glass transition temperature of PVC-N3 can be correlated with the covalently bond triazole which increases the distance between PVC chains. Thermal stability of azide-functionalized PVC carried out by thermogravimetric analysis (TGA) was enhanced than PVC modified with DEHP. The migration test for modified PVC, in four different solvents, was found to be near-zero (Fig. 7.2). The elongation at break was found to be 360.7% and the tensile strength at break was 16.2 MPa. All results demonstrate that the PVC plasticized by chemical reaction could be used for applications with durability requirements.

Fig. 7.2 The degree of migration of plasticizers in different solvents. Test conditions: temperature 23 ± 2 °C, humidity 50 ± 5%, time 24 h (adapted from Jia et al. [1])

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Industrial Scale of PVC-Bio-Based Plasticizers

While design of bio-based for PVC has been extensively studied and implemented at laboratory scale, there is a growing interest in industrial field. Growing environmental concerns owing to release of carbon footprints into the atmosphere is likely to challenge industry participant’s growth. Investments in research to develop bioproducts are likely to open up opportunities for PVC market growth. There are known recent developments of renewable modifiers and bio plasticizers market, which are phthalate-free flexible vinyl compounds and help in reducing carbon footprints. Therefore, METABOLIX has developed renewable modifier based on bio PHA (polyhydroxyalkanoate) copolymers offering enhanced processing and toughening. Traditional plasticizers decrease the low-temperature performance of PVC compounds [44]. Introduction of poly-3-hydroxybutyrate or copolymers of poly(hydroxybutyrate) into PVC led to improve the processing windows [US 20140088233A1]. Companies such as BioVinyl, Galata Chemicals, and Tecknor Apex Co. have developed plasticizers which are phthalate free based on renewable content [https:// www.gminsights.com/industry-analysis/synthetic-and-bio-polyvinyl-chloride-pvcmarket]. Evonik, an industrial group from Germany, one of the world leaders in specialty chemical, has been developed a phthalate-free plasticizer 1,2-Cyclohexane dicarboxylic acid diisononyl ester [https://docplayer.net/65511310-Play-it-safe-with-thelatest-plasticizers-degradable-additives-the-big-debate-adding-value-withfunctional-fillers.html.]. Dow Wire & Cable has introduced DOW ECOLIBRIUM™ Bio-Based Plasticizers, a new family of phthalate-free plasticizers for use in wire insulation and jacketing that are made from nearly 100% renewable feedstocks. PolyOne, in conjunction with ADM, has commercialized a soy-based plasticizer that can directly replace butyl benzyl phthalate (BBP), which has issues concerning toxicity and price volatility. Based on the chemistry, PolyOne’s bio-based plasticizer is very compatible with PVC resin and has been applied to flooring and caulk, and sealant products that can be used in sustainable building projects [http://news.bio-based.eu/ developments-in-bio-based-plasticizers/]. POLYSORB ID 37 containing isosorbide diesters produced from fatty acids of vegetable origin and isosorbide obtained by simple modification (dehydration) of a derivative of glucose, sorbitol was developed by ROQUETTE for soft PVC [www. roquette.com]. Proviron (Germany) commercializes different high-quality non-phthalate plasticizers and bio-based green plasticizers for PVC film applications, general-purpose plasticizer for PVC [www.proviron.com].

7 Bio-Based Plasticizers for Polyvinylchloride (PVC)

7.3

155

Conclusions and Future Trends

Currently, the most widely used commercial plasticizers for flexible PVC materials are phthalate compounds, for example, dioctyl phthalate (DEHP); however, these phthalates easily migrate to external media causing deterioration of PVC products. In addition, the use of phthalate plasticizers has been banned due to suspected endocrine-disruption activity caused by their leaching out of medical plastics, toys, and children’s articles. In order to replace the conventional plasticizers, the new plasticizers synthesized from renewable resources have received much attention over the past decade. The challenge in the finding of proper plasticizers for PVC at industrial scale is to synthesize plasticizers from economical and sustainable and availability materials, which do not affect the environment. Also, the PVC modified with bio-based plasticizers should have excellent thermal and mechanical properties, as well as low values of exudation test, migration, and volatility. The presented data in this paper revealed that the bio-based plasticizers led to lower stress and modulus, but the increased flexibility of PVC material, extending its application area. The degree of plasticizer migration depends on the compatibility of the plasticizers with PVC, the polarity and structure of the plasticizer, temperature, and the surrounding media, and other conditions. Development of various applications and competent price for obtaining and validation of bio-based plasticizers will be critical to PVC market penetration. However, the use of renewable resources for production of green plasticizers for PVC represents a promising option to overcome the environmental problems caused by phthalate plasticizers. Potential substitution of PVC with bio-PVC or other biodegradable polymers should be taken into consideration.

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Chapter 8

Polyvinylchloride (PVC)/ Polysaccharides Blends Andrzej Iwanczuk and Joanna Ludwiczak

Abstract Polyvinylchloride (PVC) is on top of the three mostly produced synthetic polymers. Although PVC presents many benefits such as high impact resistance, light weight, temperature capability, etc., it cannot be easily recycled and therefore its wastes may be landfiled for ages. These factors made scientists looking for capable biodegradable additives that would lead to faster degradation of PVC matrix. Several of the most popular polysaccharides materials used in blends with PVC are presented in this chapter. The most known are cellulose, chitin/chitosan, starch and glycogen. The influences of polysaccharides on PVC blends mechanical properties, as well as its biodegradation have been described. One part of the chapter has been dedicated to PVC/polysaccharides compatibility.




Keywords PVC blends Chitosan Compatibility of PVC blends

8.1


Cellulose
Starch
Glycogen


Introduction

Polysaccharides are polymeric carbohydrate molecules made of long chains of monosaccharides that are bound together by glycosidic linkages. They are an important class of biological polymers. Their function in living organisms is either structure- or storage-related. The most known storage polysaccharides are starch and glycogen, while widely available are structural ones such cellulose and chitin/ chitosan.

A. Iwanczuk (&)
J. Ludwiczak Faculty of Environmental Engineering, Wrocław University of Science and Technology, Wrocław, Poland e-mail: [email protected] J. Ludwiczak e-mail: [email protected] © Springer Nature Switzerland AG 2022 V. P. M. and R. N. Darie-Nita (eds.), Polyvinylchloride-based Blends, Springer Series on Polymer and Composite Materials, https://doi.org/10.1007/978-3-030-78455-3_8

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Starch is a polymeric carbohydrate produced by most green plants. It consists of two types of molecules: the linear and helical amylose (75–80% by weight) and the branched amylopectin (20–25% by weight). Glycogen containing glucose is a form of energy storage for humans, animals, fungi and bacteria. In has a structure similar to amylopectin, however, it is more branched and compact than starch. Cellulose is an important organic and structural component of cell wall of green plants, some algae and oomycetes. It is considered as the most abundant organic polymer on Earth. Its content of cotton fiber is around 90%, of wood 40–50% and of hemp approximately 57% [1, 2]. Chitin as a derivative of glucose, on the other hand, may be described as cellulose with one hydroxyl group on each monomer replaced with an acetyl amine group. It is translucent, resilient and quite tough. It is the main component of cell walls in fungi, crabs, lobsters, shrimps, insects, etc. Chitin is not soluble in water. Therefore, from the commercial point of view more important is chitosan (soluble in water), which is produced by deacetylation of chitin [3]. Due to their non-toxicity polysaccharides are mainly used in cosmetic and pharmaceutical applications. Nonetheless, as cellulose, starch, or chitin/chitosan can be obtained from renewable resources, there is an interest in using them as organic fillers in petroleum-based polymer composites. Among others, the main advantage of polysaccharides is their biodegradability which has been recently reviewed [4, 5].

8.2 8.2.1

PVC/Polysaccharides Blends PVC/Chitosan Blends

Chitosan (CS) is a biomaterial characterized by its biodegradability, biocompatibility with human tissues, antimicrobial and antifungal activities. Therefore has been found to be a useful and proposed in many different fields. Because of its excellent mechanical strength, nontoxicity, film forming ability, high permeability and low cost highlights the potentiality of chitosan as additive for PVC-based composites. Moreover, chemical modification of the amino groups of chitosan led it to change for a hydrophilic structure and enhanced compatibility with nanoparticles and other polymers [6–8]. CS was found as a novel coupling agent for PVC composites with wood flour (WF/PVC) that improved interfacial adhesion. In their study Xu et al. [4] aimed at investigating the effects of adding CS of varied addition amounts and particle sizes on thermal and rheological properties of PVC/WF composites. They have analyzed Vicat softening temperature (VST), differential scanning calorimetry (DCS), thermogravimetry (TGA) and torque rheometry. Main formulations of WF/PVC have been shown in Table 8.1.

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Table 8.1 Main formulation of WF/PVC composites [9] Sample codes

WF (phr)

CS (phr)

Size distribution of CS (mesh)

Silane coupling agent (phr)

WF/PVC WF/PVC/CS-10 WF/PVC/CS-20 WF/PVC/CS-30 WF/PVC/CS-40 WF/PVC/SA-5 WF/PVC/CS-a WF/PVC/CS-b WF/PVC/CS-c WF/PVC/CS-d

40 40 40 40 40 40 40 40 40 40

0 10 20 30 40 0 25 25 25 25

0 80–100 80–100 80–100 80–100 80–100 100–140 140–180 180–220 >260

0 0 0 0 0 5 0 0 0 0

It has been found that functional amino-groups in the molecular chains of chitosan are able to engender so-called a “bridge” link between natural reinforcement and PVC matrix. That phenomenon has been verified by thermal analyses. Authors found that an optimum addition amount (30 phr) with the particle size (180–220 mesh) may increase heat resistance capacity, thermal stability as well as glass transition temperature. Regarding rheological properties, at higher addition level of CS, longer fusion time and higher heat capacity of compounds have been observed. While smaller particle size level of CS resulted in lower frictional forces and reduced heat by shearing. Additionally, it has been noted that torque decreased rapidly to approximately zero after processing stage passed its stability when the addition of CS exceeded 20 phr. The influence of CS on torque rheological behaviour of wood flour (WF) /CS/ PVC have been measured by a torque rheometer at various temperatures (175 and 185 °C) and rotation speed (30, 45, 60 and 75 rpm) [9]. The torque rheological parameters have been also calculated based on the Marquez model and Arrhenius equation. The natural amine presents in CS possess a similar function as well-known chemical coupling agents with amino-groups. Their main role is to strengthen the interfacial adhesion between matrix and natural reinforcements such WF in PVC composites. It has been found that the torque rheological curves of WF/CS/PVC composites have been similar to those without CS. Addition of CS to the composite resulted in higher equilibrium temperature and torque at a constant temperature and rotation speed. Moreover, the rheological properties of WF/CS/PVC composites have not shown significant enhancement compared to “pure” WF/PVC composites. Thus the process technology of WF/CS/PVC in industrial production could be controlled in the same way as WF/PVC except for relatively higher temperature.

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CS exhibits high antimicrobial activity against pathogenic micro-organisms and have been proposed in many different field, including medicine, food, pharmaceuticals, etc. [10–12]. In their work [8] Khan et al. studied the use and effect of CS on the properties of PVC prepared by thermo-mechanical mixing. Several compositions of the PVC/CS have been prepared with a CS content varied from 0 to 40 wt%. The results of tensile properties show that the addition of CS to PVC causes the slight increase of composite stiffness. It has been found that PVC/CS compounds exhibit a higher Young’s modulus comparing to pure PVC. Meanwhile, there has been no notable reduction in tensile strength observed. The presence of CS caused small increasement in the storage and loss moduli. SEM analysis of the specimen fracture surfaces has shown no bonding between CS and PVC. According to TGA analysis, the addition of CS has not resulted in any negative impact on thermal stability of PVC composites. Considering its good antimicrobial activity, CS seems to be highly promising filler for PVC-based composites. Antibacterial activity is another feature of CS that has been observed [13, 14]. Based on the results of FTIR, SEM and DMA analysis, the ability for interface self-reinforcement of CS has been revealed. Exposure of PVC/WF/CS composites to moisture for long term resulted in significant increase in water absorption. There has been sufficient antibacterial activity observed when adding the certain amount of CS to compound. As much as 30 phr of chitosan with the particle size of over 260 mesh has been considered as the best selection for preparing very good interfacial self-reinforcing and antibacterial composites of PVC with WF. Acid–amine CS derivative has been used as a modifier for ZnO particles that have been incorporated into PVC matrix in order to reinforce it. It has been found that thermal properties of PVC/ZnO nanocomposites have been improved comparing to neat PVC [15]. Addition of 1 mass% of CS and aliphatic–aromatic polyamide (PA) resulted in enhanced thermal stability. According to mechanical tests, it has been concluded that three-component PVC nanocomposite system exhibited a very good effect on the tensile strength and flexural modulus of PVC improvement. Results of the work indicated that the combination of CS and PA is promising in order to improve thermal, combustion and tensile properties of PVC.

8.2.2

PVC/Starch blend

Starch is well-known, low-cost, biodegradable and available polymer that can be used as reinforcement in polymer composites. Normally starch is used for the packaging industry as a blend with popular biodegradable aliphatic polyesters, such as Ecoflex (BASF, Germany) or Bionolle (Showa Highpolymers, Japan). Starch in composites can be used in a form of granules or so-called “thermoplastic starch”. With the addition of certain amount of plasticizier (15–30 wt%) starch granules can be plasticized (destructurized). The most popular starch plasticizers are water,

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glycerol, or sorbitol. Under shearing forces at 90–180 °C starch melts and creates an amorphous material known as destructurized starch or TPS (thermoplastic starch) [16].

8.2.2.1

Starch Influence on Mechanical Properties and Biodegradation of PVC Composites

The influence of potato starch on the properties of PVC plasticized with di (2-ethyl-hexyl) adipate (DOA) has been examined [17]. Authors have focused mainly on the mechanical properties, optical microscopy, infrared spectroscopy, etc. Degradation tests in simulated soil have been performed as well. Six mixtures have been prepared. Concerning mechanical properties, it has been found that in general, the greater the starch contents of the mixture, the lower the tensile strength at break is. Thus, the presence of starch granules decreased the flexibility of PVC composites. As has been shown, for instance, a starch content of 40 phr has reduced the tensile strength at break for as much as 44% in comparison to samples without starch. Addition of starch to PVC matrix has also influenced the elongation at break, meanwhile however increased Young’s modulus. Tensile properties results indicate that the addition of starch in the mixtures resulted in a more rigid material, probably due to the formation of new intermolecular interactions. PVC/DOA/starch composites have been stored in soil compost containing 25% loamy silt, 23% organic matter (cow manure), 23% sand and 31% distilled water (all w/w). Biodegradability has been monitored by the variation on mass after specified periods in the soil compost. The results of mass loss by PVC and their blends with starch after aging for 6 months in soil have been presented in the work. There has been observed a slow and gradual loss of weight during aging in simulated soil. The average mass loss in the first 2 months of aging was 1.67% and it has been slightly increased to 1.97% after 4 and 3.37% after 6 months. It has been concluded that the fact of relatively low rates of degradation in simulated soil may have been caused by starch granules encapsulation in the PVC resin. Considering the best set of mechanical properties and higher degradability a starch content of 10–20% is the most suitable for PVC composites with DOA.

8.2.2.2

Solution Blending PVC/starch Acetate

There has been one attempt of examination the compatibility of PVC/starch acetate (STAc) blends in solution through viscometric studies, ultrasonic and density measurements [18]. Authors have studied the compatibility of prepared blends in solid states through scanning electron microscopy (SEM) and FTIR of solution-cast films. There have

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been several polymer solution blends of PVC/STAc prepared: 20/80, 30/70, 50/50, 70/30 and 80/20. Theoretically, the blends of PVC with STAc are incompatible and unfortunately all test performed led to the same conclusion. Moreover, morphological studies also showed that the STAc particles distribution in the PVC matrix is uniform.

8.2.2.3

Biodegradation of PVC/starch Blended Films

PVC is the third most widely produced polymer is as well a huge source of pollution. Mostly physical and chemical methods for degradation and recycling are used. One of the proposed methods of PVC degradation is to isolate microorganisms from the soil that are able to degrade PVC films blended with starch [19]. In order to perform test of biodegradation PVC/starch blended film has been prepared by casting. Thin films have been buried in the garden soil for a period of 3 months. The results of the experiment showed that the fungal strain P.chrysosporium PV1 was able to not only change the polymer surface from smoother to rougher, but also to disrupt PVC/starch films. This is because by blending polymers with additives one can reduce the molecular weight of the polymer what makes it easier for microorganism to degrade.

8.2.3

PVC/Cellulose and Wood Flour Blends

A wide group of materials manufactured on the market are composites based on PVC with the addition of wood fibers/flour. Wood is classified as a lignocellulosic material, which consists of the main components (cellulose, hemicellulose and lignin) and minor components (ash and extract) [20]. Wood is composed about 60– 75% cellulose, 20–30% lignin, 1–10% extracts and 0–0.5% ash [21]. Composites of wood materials (WPC) are produced by dispersing wood fibers/flour (WF) in a molten polymer matrix using extrusion, thermoforming and injection molding process. Composites of PVC filled with wood show improved performance over wood in the following properties: termite resistance, weathering aging, less colour change, better dimensional stability, less moisture absorption. It can be nailed, screwed, sawed, cut and glued like wood by conventional tools without any special skills required. PVC/wood composites can be used for decorative applications, e.g., cornices, doors and siding [22]. However, due to the poor interactions between the hydrophilic polar properties of WF and the hydrophobic non-polar properties of PVC, PVC/WF composites are more fragile and have less impact resistance than pure PVC products. Djidjelli et al. [23] prepared composites using PVC as a polymer matrix and 10, 20, 30 wt.% of WF as a filler. The obtained results indicate that the mechanical properties of the composite deteriorate when the content of wood flour increases. On the other hand, this filler content has little effect on thermal properties. The

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authors stated that the PVC/WF composite can be produced by conventional techniques; however, the wood flour content should not exceed 20%. One of the research directions is to improve the mechanical properties of WPC composites, for example by adding carbon nanotubes (CNTs). CNT has an extremely high modulus of elasticity, good thermal, electrical and optical properties. Due to these characteristics, it is expected that when the polymer is reinforced with CNT, the resulting polymer/CNT composites will exhibit better properties than the unfilled polymer. Faruk and Matuana [24] developed a novel method of obtaining a better dispersion of nanoparticles (CNTs) in PVC matrix using a melt mixing process. The rigid PVC reinforced with CNT was used as a matrix in the production of PVC/WF composites. The addition of CNT to PVC matrix significantly improved the strength and modulus, irrespective of the amount of filler were used (1, 3, 5, 7.5, 10 wt.%). The optimal amount of CNT about 5 wt.% were obtained. A suitable CNT dispersion in PVC/CNT composites improved mechanical properties, however, a significant improvement when chitin (6.67 wt.%) as the coupling agent was obtained. Foamed PVC/WF blends The polymer foams made of PVC/WF composite in the foaming process are very popular in recent years. Rigid foams have good mechanical properties, low density, which allows reducing costs and improving the thermal insulation properties of materials. The polymer foams are obtained by means of physical and chemical blowing agents, in a continuous (extrusion) [25, 26] and batch process [27–30]. Depending on the type and process conditions, foams with large or micro-pores are obtained, thanks to lightweight materials with the desired properties can be produced in a controlled manner. A microcellular polymer is characterized by a cell-population density in the range of 109–1015 cells/cm3 and cell sizes in the range of 0.1–10 m. Mengeloglu and Matuana [31] investigated the effect of the type of chemical blowing agents (CBA) (endothermic and exothermic) and concentrations, as well as the influence of all-acrylic processing aids on cell density and morphology of foamed PVC/wood flour composites. The density of PVC/WF foams was reduced regardless of the amount of blowing agent. The size of the cells was dependent on the type of CBA. The smaller cells in foamed composites were produced using the exothermic compared to endothermic foaming agent. The experimental results indicate that the addition of all-acrylic processing aids ensures not only the ability to achieve densities comparable to that achieved in pure PVC foam, but also with the potential to produce rigid PVC/WF foams without the use of any foaming agents. The same authors [26] characterized the mechanical properties of extrusion foamed neat rigid PVC and rigid PVC/WF composites by using endothermic and exothermic CBA. Foaming process improved the specific elongation at break (ductility) of the samples. However, the tensile strength and modulus of the samples have deteriorated, irrespective of the chemical blowing agent type. In addition, experimental results indicated that foaming reduced the Izod impact resistance of both materials. A comparison between batch and extrusion processing was

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investigated. Polymer foams with very fine cellular structure obtained in batch process exhibit better impact strength than foams with larger cells obtained in extrusion process. Good mechanical properties can be obtained when polymer foams have evenly distributed cells of small dimensions. The addition to the composite of nanoparticles (clays or carbon nanotubes) inhibits cell growth in WPC. It was reported that the addition of clay improved the morphology of WPC foamed cells [32]. Despite the unique properties of individual carbon nanotubes (CNTs), their poor processability hindered their use as reinforcing and nucleating agents for WPC polymers and foams. Due to the very high surface energy, nanotubes tend to aggregate and are difficult to disperse in the polymer matrix [33]. Ghasemi et al. [34] presented an analysis of the morphology and mechanical properties of poly(vinyl chloride)/(wood flour)/(multi-wall carbon nanotubes) (PVC/WF/MWCNTs) foams. The nanocomposites were prepared in an internal mixer and foamed using a batch process. Nanoparticles were functionalized by sodium hypochlorite solution, foaming was carried out by using azodicarbonamide as a chemical blowing agent. SEM micrographs showed that the cell size decreased and the cell density was increased when MWCNTs were added. Lower densities of nanocomposite foams with functionalized MWCNTs were obtained in comparison with the other materials. Functionalized MWCNTs affected improve interaction with the polymeric matrix, therefore PVC/MWCNTs foams characterized by good mechanical properties.

8.3

Compatibility of PVC/Polysaccharides Blend

High degree of moisture absorption by the filler, its poor wettability, poor interfacial adhesion of fillers and polymer matrix is a common problem for PVC blends, including those with polysaccharides. The interactions between matrix and filler are crucial for the properties of polymer composites. It is known that good interfacial adhesion allows for efficient transfer of stresses between the matrix and fillers, which is helpful for the composites to absorb more energy and improve its mechanical properties. Therefore, in the case of PVC/polysaccharides blends, compatibility is important and there are many methods available for this purpose, such as graft polymerization, addition of a compatibilizer or coupling agent. However, various control conditions should be considered in the reactions, such as the content of compatibilizers or initiators, temperature and time of reaction. In the literature, many compatibilizers and coupling agents are described to improve the compatibility of PVC blends with polysaccharides.

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PVC/Wood Blends

In order to promote the interfacial adhesion between the hydrophobic PVC and hydrophilic wood flour (WF), the chemical coupling agents, such as isocyanate, polymethylenepolyphenyl isocyanate, maleated polypropylene, silane, aminosilane were used [35–39]. Ali et al. [40] investigated the high-volume composite to reduce costs of materials. In order to obtain WPC composites, PVC and wood fibers with a content of 20–60% by weight were used. Improved mechanical properties for the high wood content were possible due to the strengthening of the low impacts of hydrophobic PVC and hydrophilic wood. A new coupling agent has been developed that includes polystyrene, poly(methyl methacrylate) and maleic anhydride. It has been found that it is possible to obtain a highly filled composite using a coupling agent and other additives. In conclusion, thanks to appropriate modifications, the most economical and efficient wood-PVC composite can be formulated. Matuana et al. [41] investigated aminosilane as adhesion promoter, improving significantly the tensile strength of the PVC/wood composites. Authors suggested that treated cellulosic fibers can react with PVC to form chemical bonds. Other treatments (dichlorodiethylsilane, phthalic anhydride and maleated polypropylene) were found to be ineffective, giving strengths similar to those of composites with untreated cellulosic fibers. Shah et al. [42] proposed chitin and chitosan, two natural polymers, as novel coupling agents for PVC/WF composites. It was reported, that the natural amine in chitosan, the most abundant naturally occurring amino-polysaccharide, has similar effects to chemical coupling agents with amino groups. The improvement of PVC/WF composite properties was achieved by adding small amounts of chitosan (0.5 wt%) and chitin (6.67 wt%). Addition of natural polymers improved the mechanical properties (flexural strength about 20%, flexural modulus about 16% and storage modulus about 33–74%) compared to PVC/WF composite without coupling agent. In another work [43], various amounts and particle sizes of chitosan as a coupling agent were tested. It was found that an appropriate amount of CS can cause a “bridge” link between PVC matrix and wood flour. The optimum amount of additive (30 phr) with particle size (180–220 mesh) can increase thermal efficiency, glass transition temperature of composites and thermal stability at an early stage of degradation. Due to the large amount, non-toxicity, environmentally friendly feature and low cost compared to many other synthetic coupling agents, CS can find application as biopolymer coupling agent. Xu et al. [44] studied the effect of adding CS to the PVC/WF blend to improved compatibility and thermal stability of material. The thermal degradation temperature of PVC/WF composites increased after adding CS. It was explained that the thermal stability of PVC/WF/CS blends was effectively promoted because the interfacial blocking ability was enhanced by the autocatalytic action of HCl in the weakening of the dehydrochlorination of PVC chains. Yue et al. [45] found that the lignin amine treatment improved the mechanical properties of the PVC/WF composite, as in the case of the aminosilane. The tensile

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and impact strength of composites obtained using 30 phr of wood flour treated with 2 wt% of lignin amine increased by 21.0% and 43.9% compared to composites with untreated wood flour. Improvement was also achieved in the dispersion of WF in the polymer matrix and the reduced water absorption of composites. SEM images of the selected materials have been presented in Fig. 8.1. Jiang and Kamdem [46] proposed a copper ethanolamine solution (Cu-EA) for the WF treatment to improve PVC/WF interfacial adhesion. Mechanical properties (impact strength, flexural strength and flexural toughness) were significantly improved by the WF copper amine treatment. The impact strength was increased up to around 45% when 0.2 wt% Cu was used. Improvement of about 36% for the flexural strength and about 40% for flexural toughness were also achieved. The optimum Cu concentration range in terms of the mechanical properties was 0.2–0.6 wt% of WF. Microscopic images showed that Cu-amine treatments improved interfacial adhesion between PVC and WF.

Fig. 8.1 SEM images of PVC/wood-flour (WF) composites: a Rigid PVC; b PVC-30UWF; c PVC-30LWF (2 wt% lignin amine treated); d PVC-30KWF (1 wt% aminosilane treated) [45]

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Organomodified montmorillonite (OMMT) and WF surface-modified by silane coupling agent were prepared by Zhao et al. [47]. OMMT was modified using cetylalkyl trimethyl amine bromide. PVC/WF/OMMT composites were obtained using melt-blending and extrusion process. Addition of organically intercalated MMT improved the mechanical properties and the fire retardancy of the composites. The impact strength and the tensile strength of PVC/WF composite were increased by 14.8% and 18.5%, respectively. Addition of silane as a coupling agent effectively improved the interfacial compatibility between components.

8.3.2

PVC/Chitosan Blends

Another field of research, widely described in the literature, is the compatibility of the PVC/CS mixture. Sobahi et al. [48] focused on the compatibility of PVC/CS blend using a graft polymerization. First, the authors mixed PVC with CS using simultaneous casting of separate solvents in various proportions. In the next step, PVC and CS solutions were mixed at the room temperature. After evaporation of the solvents, the blend were obtained. A similar procedure was performed in PVC/ CS blends with an addition of dithizone, as a carrier-mediating material for different metal ions. The results showed that the described method allows obtaining a proper dispersion between components; however, it depends on the conditions in which they were mixed. Liu et al. [49] proposed the possibility of MA grafting on CS using Cu (III) CS as a redox initiator. The results showed that, compared to other initiators, Cu (III) was both an efficient, as well as a cheap initiation system. They suggested that Cu (III) obtained from CuSO4 • 5H2O is cheaper and more efficient than other initiators. The graft copolymer was used as compatibilizer in blends of PVC/CS. The SEM images and DSC thermograms showed that the graft co-polymer improved the compatibility of the blend. Another initiator, described by Liu et al. [50], diperiodatoargentate [Ag(III)]-chitosan was used to initiate the graft copolymerization of methyl acrylate (MA) onto chitosan. Authors obtained a low energy of the activation of the reaction using the Ag (III) chitosan, carried out the graft copolymerization at a mild temperature (35 °C). Chitosan-g-PMA improved the compatibility of the two chitosan and PVC phases. Microscopic examination confirmed that Ag(III)-chitosan can be an effective compatibilizer for PVC/CS blend. Cui et al. [51] prepared a calcium sulfate whisker (CSW) coated with glutaraldehyde crosslinked chitosan (GACS) to reinforce PVC matrix. The optimum concentration of both CS and glutaraldehyde (GA) about 0.05 wt% were obtained. The mechanical analysis confirmed that the modified CSW/PVC composite exhibits much better mechanical properties than those of unmodified CSW/PVC composite and pure PVC. In addition, microscopic images show that the modified CSW has a strong interfacial adhesion with PVC matrix.

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Compatibilization of PVC/Starch Blends

Starch addition to polymer matrices usually leads to enhanced brittleness. In many cases, the incorporation of core–shell rubber (CSR) particles has become popular aiming their toughness enhancement [52, 53]. There has been some work done in order to improve compatibilization of PVC/starch composites using cellulose acetate (CA) and the subsequent toughness with addition of CSR particles [54]. Hybrid system toughness has been compared with the neat PVC at equal CRS number densities. The starch content to the PVC system varied from 0 to 25 phr. Among the other resulted is has been found that comparison of toughening efficacy between pure PVC and PVC/starch/CA-compatibilized system with 20 phr of the CSR particles of methyl methacrylate-butadiene-styrene (MBS) showed much higher impact strength and lower brittle-ductile transition.

8.4

Conclusions

As described in the chapter, polysaccharides such as chitosan, cellulose, wood flour and starch are mixed with PVC. Polysaccharides have many benefits; in particular, they are natural and cheap components. Unfortunately, the properties of PVC/ polysaccharide blends are not always satisfactory because of poor interfacial adhesion of fillers and polymer matrix. For this purpose, compatibility is used, including by addition of silane, aminosilane, isocyanate and others, as well as grafted copolymers. It was also reported that chitosan and chitin can act as a coupling agent to improve the interfacial compatibility between PVC and wood flour. Compatibility affects the improvement of mechanical, thermal properties and the reduced water absorption of composites. Polystyrene, poly (methyl methacrylate) and maleic anhydride were also used as a compatibilizer. Thanks to such a modification it is possible to obtain highly filled PVC composites with the addition of even 20–60% wood fibers. The addition of a large amount of filler to the polymer matrix allows reducing the cost of the composite. It was also shown that the addition of polysaccharides positively affects the degradation of the composite with the PVC matrix. The molecular weight of the polymer is reduced by mixing polymers with additives, which facilitates degradation by microorganisms.

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3. Bedian L, Villalba-Rodríguez AM, Hernández-Vargas G, Parra-Saldivar R, Iqbal HMN (2017) Bio-based materials with novel characteristics for tissue engineering applications—a review. Int J Biol Macromol 98:837–846 4. Pushpamalar J, Veeramachineni AK, Owh C, Loh XJ (2016) Biodegradable Polysaccharides for controlled drug delivery. ChemPlusChem 81(6):504–514 5. Tokura S, Nishimura S-I, Sakairi N, Nishi N (1996) Biological activities of biodegradable polysaccharide. Macromol Symp 101(1):389–396 6. Liao J-D, Lin S-P, Wu Y-T (2005) Dual properties of the deacetylated sites in chitosan for molecular immobilization and biofunctional effects. Biomacromol 6(1):392–399 7. Salehi R, Arami M, Mahmoodi NM, Bahrami H, Khorramfar S (2010) Novel biocompatible composite (Chitosan–zinc oxide nanoparticle): preparation, characterization and dye adsorption properties. Colloids Surf, B 80(1):86–93 8. Khan R, Kaushik A, Solanki PR, Ansari AA, Pandey MK, Malhotra BD (2008) Zinc oxide nanoparticles-chitosan composite film for cholesterol biosensor. Anal Chim Acta 616(2):207– 213 9. Xu K, Zheng Z, Chen T, Li K, Zhong T (2015) Study on the torque rheological behavior of wood flour/chitosan/polyvinyl chloride composites. BioResources [Internet] [cited 2018 Nov 5] 10(2). Available from: http://ojs.cnr.ncsu.edu/index.php/BioRes/article/view/6759 10. Wei D, Sun W, Qian W, Ye Y, Ma X (2009) The synthesis of chitosan-based silver nanoparticles and their antibacterial activity. Carbohyd Res 344(17):2375–2382 11. dos Santos DS, Goulet PJG, Pieczonka NPW, Oliveira Osvaldo N, Aroca RF (2004) Gold nanoparticle embedded, self-sustained chitosan films as substrates for surface-enhanced raman scattering. Langmuir 20(23):10273–10277 12. Liu X, Hu Q, Fang Z, Zhang X, Zhang B (2009) Magnetic chitosan nanocomposites: a useful recyclable tool for heavy metal ion removal. Langmuir 25(1):3–8 13. Xu K, Li K, Zhong T, Xie C (2014) Interface self-reinforcing ability and antibacterial effect of natural chitosan modified polyvinyl chloride-based wood flour composites. J Appl Polym Sci [Internet] [cited 2018 Oct 31] 131(3). Available from: https://doi.org/10.1002/app.39854 14. Xu K, Li K, Tu D, Zhong T, Xie C (2014) Reinforcement on the mechanical-, thermal-, and water-resistance properties of the wood flour/chitosan/poly(vinyl chloride) composites by physical and chemical modification. J Appl Polym Sci [Internet] [cited 2018 Oct 31] 131(18). Available from: https://doi.org/10.1002/app.40757 15. Hajibeygi M, Maleki M, Shabanian M, Ducos F, Vahabi H (2018) New polyvinyl chloride (PVC) nanocomposite consisting of aromatic polyamide and chitosan modified ZnO nanoparticles with enhanced thermal stability, low heat release rate and improved mechanical properties. Appl Surf Sci 1(439):1163–1179 16. Tanzi MC, Farè S (eds) (2017) Characterization of polymeric biomaterials. Woodhead Publishing, an imprint of Elsevier, Duxford, United Kingdom, 486 p (Woodhead Publishing series in biomaterials) 17. Rosa DS, Rios AR, Viana HM, Tavares MIB (2016) Characterization of poly(vinyl chloride) compounds containing different levels of starch. J Vinyl Add Tech 22(4):396–404 18. Thakore IM, Desai S, Sarwade BD, Devi S (1999) Evaluation of compatibility of poly(vinyl chloride)/starch acetate blends using simple techniques. J Appl Polym Sci 71(11):1851–1861 19. Ali MI, Ahmed S, Javed I, Ali N, Atiq N, Hameed A et al (2014) Biodegradation of starch blended polyvinyl chloride films by isolated Phanerochaete chrysosporium PV1. Int J Environ Sci Technol 11(2):339–348 20. Hon DN-S, Shiraishi N (2000) Wood and cellulosic chemistry, Second edn, Revised, and Expanded. CRC Press, 930 p 21. Marra AA (1992) Technology of wood bonding: principles in practice. Van Nostrand Reinhold, New York 22. Chetanachan W, Sookkho D, Sutthitavil W, Chantasatrasamy N, Sinsermsuksakul R (2001) PVC wood: a new look in construction. J Vinyl Addit Technol [Internet] [cited 2018 Oct 23] 7(3):134–137. Available from: https://doi.org/10.1002/vnl.10280

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23. Djidjelli H, Martinez‐Vega J-J, Farenc J, Benachour D (2002) Effect of wood flour content on the thermal, mechanical and dielectric properties of Poly(vinyl chloride). Macromol Mater Eng [Internet] [cited 2018 Oct 17] 287(9):611–618. Available from: https://doi.org/10.1002/ 1439-2054(20020901)287:93.0.CO;2-L 24. Faruk O, Matuana LM (2008) Reinforcement of rigid PVC/wood-flour composites with multi-walled carbon nanotubes. J Vinyl Addit Technol [Internet] [cited 2018 Oct 18] 14 (2):60–64. Available from: https://doi.org/10.1002/vnl.20145 25. Foam Extrusion: principles and practice, Second edn—Google Książki [Internet] [cited 2018 Oct 19]. Available from: https://books.google.pl/books?id=l0TOBQAAQBAJ&pg= PA487&lpg=PA487&dq=matuana,+park,+cellular+1997&source=bl&ots= ZBjEsmIdag&sig=1VRv_RI3jnyG3qJ8cXumSpY6b30&hl=pl&sa=X&ved= 2ahUKEwiesPCSrJLeAhXrtIsKHWukAPIQ6AEwAHoECAkQAQ#v=onepage&q=matuana %2C%20park%2C%20cellular%201997&f=false 26. Mengeloglu (2003) Mechanical properties of extrusion‐foamed rigid PVC/wood‐flour composites. J Vinyl Addit Technol. Wiley Online Library [Internet] [cited 2018 Oct 19]. Available from: https://doi.org/10.1002/vnl.10058 27. Matuana-Malanda L, Park CB, Balatinecz JJ (1996) Characterization of microcellular foamed pvc/cellulosic-fibre composites [Internet] [cited 2018 Oct 19]. Available from: https://doi.org/ 10.1177/0021955X9603200503 28. Processing and cell morphology relationships for microcellular foamed PVC/wood‐fiber composites|request PDF [Internet] [cited 2018 Oct 19]. Available from: https://www. researchgate.net/publication/227810526_Processing_and_cell_morphology_relationships_ for_microcellular_foamed_PVCwood-fiber_composites 29. Structures and mechanical properties of microcellular foamed polyvinyl chloride|request PDF [Internet] [cited 2018 Oct 19]. Available from: https://www.researchgate.net/publication/ 261986822_Structures_and_Mechanical_Properties_of_Microcellular_Foamed_Polyvinyl_ Chloride 30. Matuana (2001) Microcellular foaming of impact‐modified rigid PVC/wood‐flour composites. J Vinyl Addit Technol. Wiley Online Library [Internet] [cited 2018 Oct 19]. Available from: https://doi.org/10.1002/vnl.10269 31. Mengeloglu (2001) Foaming of rigid PVC/wood‐flour composites through a continuous extrusion process. J Vinyl Addit Technol. Wiley Online Library [Internet] [cited 2018 Oct 19]. Available from: https://doi.org/10.1002/vnl.10282 32. Guo G, Wang KH, Park CB, Kim YS, Li G (2007) Effects of nanoparticles on the density reduction and cell morphology of extruded metallocene polyethylene/wood fiber nanocomposites. J Appl Polym Sci [Internet] [cited 2018 Oct 23] 104(2):1058–1063. Available from: https://doi.org/10.1002/app.25778 33. Bag DS, Dubey R, Zhang N, Xie J, Varadan VK, Lal D et al (2004) Chemical functionalization of carbon nanotubes with 3-methacryloxypropyltriniethoxysilane (3-MPTS). Smart Mater Struct 13(5):1263–1267 34. Ghasemi I, Farsheh AT, Masoomi Z (2012) Effects of multi-walled carbon nanotube functionalization on the morphological and mechanical properties of nanocomposite foams based on poly(vinyl chloride)/(wood flour)/(multi-walled carbon nanotubes). J Vinyl Addit Technol [Internet] [cited 2018 Oct 23] 18(3):161–167. Available from: https://doi.org/10. 1002/vnl.20299 35. Kokta B, Maldas D, Daneault C, Beland P (1990) Composites of polyvinyl chloride-wood fibers. I. Effect of isocyanate as a bonding agent. Polym Plast Technol Eng 29:87–118 36. Kokta BV, Maldas D, Daneault C, Béland P (1990) Composites of polyvinyl chloride–wood fibers. III: Effect of silane as coupling agent. J Vinyl Technol [Internet] [cited 2018 Oct 8] 12 (3):146–153. Available from: https://doi.org/10.1002/vnl.730120306 37. Bledzki AK, Reihmane S, Gassan J (1998) Thermoplastics reinforced with wood fillers: a literature review. Polym Plast Technol Eng [Internet] [cited 2018 Oct 8] 37(4):451–468. Available from: https://doi.org/10.1080/03602559808001373

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54. Pourrahimi AM, Mohammadi N, Javadi A (2011) The toughness amplification map of poly (vinyl chloride) and its cellulose acetate-compatibilized starch alloys containing core/shell rubber particles: Possible transition to super-toughening. J Polym Sci Part B Polym Phys 49 (5):327–332

Chapter 9

Preparation of Polyvinylchloride (PVC) Membranes, Characterization, Modification, Applications, and Mathematical Model Heba Abdallah and Ayman El-Gendi

Abstract Nowadays, polymers blending technique is used to prepare membranes to produce modified membranes in performance and characterization. A mathematical model for membrane preparation in a ternary and quaternary systems for blending between polyvinylchloride (PVC) and other polymers is presented in this chapter. An extended modified Flory–Huggins theory was applied as a source for the model of blend polymers. The diffusion model is studied to discuss the immersion/precipitation step during membrane formation. Most researches indicated that the solvent volume fraction increased during the coagulation time, while the polymer solution volume fraction reduced leading to solvent removal from polymer solution during membrane formation. Keywords Mathematical model Polyvinylchloride membranes


Polymer blend
Immersion precipitation


Nomenclature Dij Binary diffusion coefficient between i and j (m2/s) DG Gibbs free energy of mixing (J/mol) Jk Flux of species k into the coagulation bath at the interface between polymer solution and coagulation bath at (y = 0) L Total film thickness (m) Mi Molecular weight of component i (kg/kmol) R Universal gas constant (J/mol/K) T Temperature (K)

H. Abdallah (&)
A. El-Gendi Chemical Engineering and Pilot Plant Department, Engineering Research Division, National Research Centre, Giza, Egypt A. El-Gendi Chemical Engineering, Faculty of Engineering, King Abdelaziz University, Jeddah, Saudi Arabia © Springer Nature Switzerland AG 2022 V. P. M. and R. N. Darie-Nita (eds.), Polyvinylchloride-based Blends, Springer Series on Polymer and Composite Materials, https://doi.org/10.1007/978-3-030-78455-3_9

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Time (s) Molar volume of component i (m3/mol)

Greek Symbols Dli /i : ni di

Change in chemical potential of component i (J/mol) Volume fraction of component i Number of moles of component I (mole) Solubility parameter (kJ1/2/m3/2)

Subscripts DSI MD MF UF NF RO FO PV GS HF NMP SEM DMF TFC TGA EA CA PMDA PASA PEAH PEG PI PEI PPSS PES PS PTMSP PVA PVDF PA PA-6 PABH

Desalination Systems, Inc. Membrane distillation Microfiltration Ultrafiltration Nanofiltration Reverse osmosis Forward osmosis Pervaporation Gas separation Hollow fiber N-methyl-2-pyrrolidone Scanning electron microscopy N,N-dimethylformamide Thin-film composite Thermogravimetric analysis Ethyl acrylate Cellulose acetate Pyromellic dianhydride Poly(amidesulfonamide) Polyetheramide hydrazide Polyethylene glycol Aromatic polyimides Polyetherimide Poly(phenylene sulfide sulfone) Polyether sulfone Polysulfone Poly(1-trimethylsilyl-1-propyne) Polyvinyl alcohol Polyvinylidenedifluoride Propionic acid Polyamide-6 p-amino benzhydrazide

9 Preparation of Polyvinylchloride (PVC) Membranes …

PAH PAN PC PP PPO PTFE PVAC PVC PVDC PVF PBS GO NP ZrO2 DMAc HA BSA NOM NIPS IP AN-MMA SEIP

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Polyamide-hydrazides Polyacrylonitrile Polycarbonate Polypropylene Polyphenyleneoxide Teflon (polytetrafluoro ethylene) Poly(vinyl acetate) Poly(vinyl chloride) Poly(vinylidene chloride) Polyvinyl formal Phosphate buffer solution Graphene oxide Neodymium phosphate Zirconium oxide N,N-dimethylacetamide Humic acid Bovine serum albumin Natural organic matter Non-solvent induced phase separation Interfacial polymerization Acrylonitrile-methyl methacrylate Solvent exchange immersion precipitation

Introduction

Polyvinylchloride (PVC) has involved not only for an unlimited consideration of its remarkable properties as mechanical and chemical resistance (to acids, halogens, or oxidants), un-expensive and good stability at elevated temperatures. But also, PVC is soluble in numerous solvents such as dimethylformamide (DMF), Nmethyl-pyrrolidinone (NMP), tetrahydrofuran (THF), and N,N dimethylacetamide (DMAc). Moreover, the hydrophobicity of PVC is high, this cause high membrane fouling during membrane performance test such as ultrafiltration (UF). For that issue, several researchers tried to adapt the drawbacks of PVC membrane. For that challenge, several modifications such as blending, grafting, and coating have been done which resulted in hydrophilic and fouling resistant membranes.

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Polyvinylchloride (PVC) Membrane Preparation Methods

Polyvinylchloride (PVC) is used in the preparation of membranes, owing to its acceptable characteristics as good mechanical strength, abrasion resistance, chemical stabilization, thermal properties, low cost, and corrosion resistance [1–3]. PVC membrane preparation is discussed in that part [4–6]. Mostly, the membranes preparation methods include phase inversion process (PI) [4], track-etching (for capillary pore membranes-MF), stretching process (for preparing MF), sintering (for preparing MF), interfacial polymerization (IP), and electro-spinning. The PVC membrane is mainly prepared by phase inversion method.

9.2.1

Phase Inversion (PI) Method

PVC membrane is mainly prepared via phase inversion method. Phase inversion (PI) process can be defined as a de-mixing process in it the initially homogeneous polymer solution is changed in a limited approach from a liquid state to a solid-state [7, 8]. Phase inversion is formed of several methods, namely: non-solvent induced phase separation (NIPS), thermally induced phase separation (TIPS), evaporation-induced phase separation (EIPS), and vapor-induced phase separation (VIPS) as shown in Fig. 9.1 [9–11]. These methods will discuss as follow. Non-solvent Induced Phase Separation (NIPS) This process is called also immersion precipitation, the casting process, and wet phase inversion [12]. Through that method, PVC membrane is prepared by several steps namely; mixing step, casting step, immersion step, and drying step as shown in Fig. 9.2. Initially, PVC is dissolved in a suitable liquid solvent. Then, the PVC polymer solution is causing a casting knife on a substrate. The cast PVC is immersed into the immersion bath as shown in Fig. 9.2. Bhran et al. [13] prepared PVC membrane using NIPS method. The PVC polymer was dissolved in tetrahydrofuran (THF) and N-Methyl-2-pyrrolidone (NMP) at room temperature. Then, the polymer solution was cast on glass using

PI

NIPS

TIPS

Fig. 9.1 PVC membrane preparation using PI

EIPS

VIPS

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Fig. 9.2 Schematic presentation of NIPS process

Fig. 9.3 Process flow sheet for preparation of PVC membranes for desalination by direct contact membrane distillation

doctor blade. After that, the casted films were immersed in water to remove any residual solvent and produce a thin film of the polymeric membrane as shown in Fig. 9.3. Polyvinylchloride/polycarbonate (PVC/PC) blend ultrafiltration membranes for water treatment were prepared via NIPS method by Behboudi et al. [2]. The polymer solution was prepared from PEG, PVC, and PC in NMP. The homogeneous solution was degassed overnight then cast onto a glass plate using an automatic casting knife. The cast membranes were immediately immersed in distilled water as non-solvent. Lastly, the membrane was dried and stored at 5 °C as presented in Fig. 9.4. The polyvinylchloride (PVC) blend ultrafiltration membranes are prepared by several authors for different application [14–16].

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Fig. 9.4 Process flow sheet for preparation of PVC membranes for water treatment

Thermally Induced Phase Separation (TIPS) [12] TIPS is based on the fact that the solvent feature usually changed (decreased) once the temperature is changed (decreased). Consequent, the de-mixing process is detected [17, 18]. Doubé and Walsh [19] studied the behavior of mixtures of poly (vinyl chloride) (PVC) with solution chlorinated polyethylene as a function of temperature and investigated the TIPS by optical, dynamic mechanical, and electron microscope techniques. PVC membrane was prepared by TIPS through studied the polymer solution in different weight ratios using tetrahydrofuran (THF) as a solvent. Evaporation-Induced Phase Separation (EIPS) PVC membranes are prepared using EIPS in different steps as follow: mixing step, casting step, and drying step. Vapor-Induced Phase Separation (VIPS) A non-solvent (as water) vapor penetrates in the polymer solution causes de-mixing/precipitation. To the best of our knowledge, no data has previously been available regarding the preparation of PVC membrane via the other methods (track-etching, stretching process, sintering and electro-spinning, interfacial polymerization). Only one study by Xu and Xu [20] Investigated the preparation of PVC hollow fiber membrane using the dry/wet-spinning technique.

9 Preparation of Polyvinylchloride (PVC) Membranes …

9.2.2

181

Modification of PVC Membrane

The limit of using for PVC polymer in membrane preparation is due to the high hydrophobicity of PVC. For that challenge, several modifications [3] such as blending [21], grafting [22] and coating have been done to improve hydrophilicity and fouling resistant membranes. Polymer blending process is not only low cost but also an effortless way for polymeric membrane preparation with amended properties [1]. For example, PVC was blended with poly(vinyl chloride-co-polyethylene glycol methyl ether methacrylate) copolymer (poly(VC-co-PEGMA)) by Zhou et al. [23], and found that the prepared membranes had improvement in hydrophilicity and antifouling properties in comparison with neat PVC membranes. In another study, PVC/CA blend ultrafiltration (UF) membranes investigated by Krishnamoorthy et al. [14], and noticed that the water flux of membranes increased whereas rejection decreased with increasing of PVC concentration in the dope solution. In other work, Peng and Sui [24] developed that preparation of PVC/PVB (polyvinyl butyral) blend membranes and reported that the water flux and hydrophilicity of the PVC/PVB membranes enhanced by the addition of PVB but rejection of egg white protein decreased slightly. In another study, Fang et al. [25] studied blending of PVC/poly(methyl methacrylate-g-polyethylene glycol methacrylate) membranes in water and ethanol immersion baths, where the observation was the hydrophilicity and antifouling properties of blended membranes were higher than that of neat PVC membrane. Alsalhy et al. [15] studied the preparation of PVC/Polystyrene blend membranes and reported that the rejection of blend membranes was higher than that of neat PVC membrane while pure water flux decreased. The effect of PVC membrane preparation parameters such as PVC molecular weight, casting solution compositions, polymer concentrations, solvents types, co-solvents, and additives was studied [26, 27]. Bodzek and Konieczny [28] studied the effect of PVC molecular weight on flat membrane structure and performance using N,N-dimethyl formamide (DMF) as a solvent and water as a non-solvent, and reported that the low casting solution concentration was preferred for preparing ultrafiltration PVC membranes. Also, the effect of the addition of filler materials as inorganic nanoparticles such as SiO2 [16], ZnO [29], and TiO2 [2] into PVC membranes have been reported. The performance of prepared PVC membrane was enhanced and antifouling properties in comparison with blank PVC membrane. The preparation offlat PVC ultrafiltration (UF) and microfiltration (MF) membrane has been investigated by numerous researchers [16, 23–28, 30] via phase inversion method. Furthermore, the preparation and structures of PVC membranes have been studied through finding the relationship between membrane structure and phase separation process [31, 32]. The preparation, structure, and transport properties of ultrafiltration membranes from PVC/carboxylated poly(vinyl chloride) (CPVC) blends and PVC/poly(vinyl pyrrolidone) (PVP) blends are reported [33, 34].

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PVC Membrane Characterization [20, 30] Polymer Solution Properties

The viscosity of polymer solution can be tested using rotational viscometer to study the effect of polymer solution concentration on PVC membrane performance and membrane properties.

9.3.2

Mechanical Properties

Tensile strength and elongation-at-break of the PVC membranes should be measured to evaluate the mechanical strength of the PVC membranes. Each sample should be tested at least three times to ensure the results in a high confidence level.

9.3.3

PVC Membrane Thickness

Before measuring the membrane thickness, it should be dried at room temperature, then using a micrometer to measure the thickness. Each membrane sample should be analyzed several times at different positions.

9.3.4

Pore Size and Porosity

Membrane porosity and mean pore size can be measured according to their dry–wet weight [35, 36]. The inner surface of the prepared blend membranes can be determined using the Brunauer–Emmett–Teller (BET) method. The Samples of known weights of the membrane are cut into long strips and placed in a glass column of the apparatus, dried, and degassed by heating at 80 °C for 3 h. The average area is determined using the BET single point.

9.3.5

Scanning Electron Microscopy (SEM) Analysis

Scanning electron microscopy (SEM) apparatus are used for detecting the surface (top, bottom) and cross-sectional morphology of PVC membrane. For SEM images, the PVC membrane membranes are cut into small slices, and then they are submerged into liquid nitrogen and fractured. The PVC membrane samples are coated with a gold layer and are observed at different magnifications.

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9.3.6

183

Atomic Force Microscopy (AFM)

PVC membrane surface morphology in terms of the mean surface roughness is determined using AFM. It is a non-optical surface imaging technique that moves towards atomic resolution. The mean roughness is defined as the value of surface, relative to the center plane. Some researchers studied the relationship between roughness and membrane performance depending on the membrane surface.

9.3.7

Contact Angles

Surface contact angles of PVC membranes are measured using contact angle apparatus (goniometer) to evaluate the surface hydrophilicity of the PVC membranes. The sessile drop technique is used to apply the water drop on the membrane surface, the membranes are air dried before measurements and contact angles between water and PVC membrane surface are measured at ambient temperature.

9.3.8

Differential Scanning Calorimetry (DSC)

The compatibility between PVC membrane compositions is studied using DSC (such as; DSC 204 F1 Pheonix, Netzsch) in nitrogen atmosphere [37]. The PVC membrane is heated from 25 to 160 °C and held at 160 °C for 5 min, followed by cooling back to 25 °C at 10 °C/min.

9.3.9

X-Ray Diffraction (XRD)

X-ray diffraction study of the prepared PVC membranes is conducted by using such as a diffractometer (D8 Advance, Bruker) equipped with monochromatic Cu-Ka radiation (k = 0.154 nm). All PVC membranes samples are analyzed in continuous scan mode with the 2h ranging from 10° to 80°.

9.3.10 Energy-Dispersive X-Ray Spectroscopy (EDX) EDX is an analytical technique, which is used for the elemental analysis or chemical characterization of the sample. The EDX analysis is performed by using a Quanta FENG 200 (FEI Company) microscope.

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9.3.11 Fourier Transform Infrared Spectroscopy (FTIR) Fourier Transform Infrared Spectroscopy (FTIR) is used to analyze organic materials and inorganic materials since; it can provide specific information about chemical bonding and molecular structure. The FTIR spectrum of PVC appears at peaks 2920 and 2840 cm−1 corresponds to C–H stretching.

9.3.12 Thermogravimetric Analysis (TGA) The thermal stability of the PVC membranes is measured using the thermal gravimetric analyzer. 5–10 mg of the sample is loaded in an Alumina pan and heated in a flow of inert atmosphere to 450 °C using a heating rate of 10 °C/min.

9.3.13 Abrasion Resistance Test To examine abrasion resistance of the prepared membranes, an accelerated testing setup is designed like the method described in [38], where 220 g of abrasive slurry containing 10 wt% of silicon carbides in deionized water was placed in a beaker. A 4 cm  4 cm piece of each type of membrane is secured in the beaker and immersed into a slurry. The slurry is then stirred slowly at least 7 days to allow the membrane to be in contact with abrasive silicon carbide. Weights of the membranes are measured before and after abrasion test to determine weight loss during the test. Table 9.1 presented the summary of membrane property and characterized apparatus.

9.4

Application of PVC Membrane

Attributable to the low price and chemical stability of Polyvinylchloride (PVC) polymer, that is appropriate for the manufacture of ultrafiltration (UF) membrane [39]. Owing to the low hydrophilicity of PVC membrane, its application in water treatment purposes is restricted since it is fouled. For that challenge, numerous modification methods have been explored to decrease hydrophobicity and to improve antifouling properties of PVC membrane. For that issue, PVC membrane properties were adapted by several techniques such as blending, grafting, and coating, a consequence of the hydrophilic and fouling [16] resistant of membranes could be enhanced [16, 22, 29] as discussed in Sect. 9.2.1 after the modification processes, the PVC membranes are applied in several applications.

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Table 9.1 Summary of membrane property and characterized apparatus or method Characterization property

Apparatus

Tensile strength and elongation of membranes The viscosity of polymer solution The membrane thicknesses Morphology and pore size Surface roughness Hydrophilicity Mass degradation Oxygen content Compatibility of membrane compositions Chemical bonding and molecular structure Elemental analysis or chemical characterization of the sample X-ray diffraction

Mechanical testing system

Abrasion resistance of prepared membrane Permeability/separation

Rotational viscometer Micrometer Scanning electron microscopy (SEM) Atomic force microscopy (AFM) Contact angle measurement Thermogravimetric analysis (TGA) X-ray photoelectron spectroscopy (XPS) DSC; 204 F1 Pheonix, Netzsch Fourier transform infrared spectroscopy (FTIR) EDX; Quanta FENG 200 (FEI Company) microscope XRD; diffractometer (D8 Advance, Bruker) equipped with monochromatic Cu–Ka radiation (k = 0.154 nm) Abrasion resistance test SET-UP Flux measurements/rejection by permeation test

The membrane is a semipermeable selective barrier between two phases or environments. It can be classified according to driving force as for shown in Table 9.2. Also, membranes can be classified according to pores size as shown in Fig. 9.5. The PVC membrane is applied in the different application as follow. Table 9.2 Membrane driving force Driving force

Process

Pressure driving processes

Microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), gas separation (GS) Pervaporation (PV)

Partial pressure driving processes Concentration gradient driving processes Temperature driving processes Electrical potential driving processes

Dialysis Membrane distillation (MD) Electrodialysis (ED)

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Fig. 9.5 Membrane processes according to membrane pore size

9.4.1

Microfiltration

Microfiltration is a process in which fine impurities with a molecular weight greater than 100 kDa such as colloids, emulsions, and bacteria are separated from liquid and gases. The pore size of this membrane is greater than 100 nm. On the bases of sieving effect, the mechanism of separation occurred according to pores dimension. Sometimes adsorptive or charge separation occurs. Compared with other separation processes, microfiltration is achieved by applying a relatively low pressure (2– 4 bar) [40]. Blending of Poly(vinyl chloride) (PVC) with poly(methyl methacrylate-co-methacrylic acid) (PM) provided high porous microfiltration membrane with high flux [41].

9.4.2

Ultrafiltration (UF)

Ultrafiltration is a separation process in which particles and species with a molecular weight ranging from 1000 to 10.000 are separated. The pore size is ranging from 2 to 100 nm. In ultrafiltration the osmotic pressure can be produced by particles and species equal few bars, thus the driving force is the hydrostatic pressure difference and ranging from 6 to 8 bars. Also, UF is achieved by sieving mechanism and the selectivity is based on the physical and chemical properties of the membrane, hydrodynamic conditions, as well as the charges and size difference of the components to be separated [42]. Blending of PVC with different percentage

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of polycarbonate produced high-performance ultrafiltration membrane, where rejection of Bovine serum albumin from synthetic solution was 98.9% using 50% of polycarbonate blending with PVC with high permeate flux [2]. Using a combination of non-solvent induced phase separation (NIPS) and thermally induced phase separation (TIPS) in PVC membrane preparation can produce ultrafiltration membranes with sponge-like/bi-continuous structures with 60% porosity and rejection of dextran solution more than 90% [43]. Other cases, polyvinylchloride (PVC) membrane was developed using graphene oxide (GO) with phase inversion method to improve membrane hydrophilicity and mechanical properties, where the addition of 0.1 wt% improved permeate flux of GO/PVC membrane from 232.6 to 430.0 L/(m2 h bar) [44].

9.4.3

Nanofiltration (NF)

Nanofiltration is a process in which the molecules have a molecular weight ranging from 300 to 1000 are separated. NF membrane has features between reverse osmosis (RO) and ultrafiltration (UF) membranes because it is performing as “loose” RO and “'tight” UF membrane. Therefore, NF is achieved by both diffusion transport and sieving mechanism. Nanofiltration membrane can be used in solute rejection but for divalent and multivalent ions such as Mg+2 and Ca+2. Rejection of salts in NF membrane is achieved by the valances of ions. The pore size of the membrane is ranging from 0.5 to 2 nm. The applied pressure is ranging from 15 to 25 bars [45]. Nanofiltration membrane was prepared using blending between poly-ether-sulfone and sulfonated polyvinylchloride, where polymers were dissolved with different ratios in solvent dimethylacetamide and provide high flux due to increase in hydrophilicity of membrane [46].

9.4.4

Reverse Osmosis (RO) Process

Reverse Osmosis membranes are used to separate salts ions under very high pressure (greater than 25 bars). Osmosis is a diffusion of fluid, water, from the region that has the low solute concentration to the region of high solute concentration through a semipermeable membrane until reaching the equilibrium fluid concentration, where the pressure difference equals the osmotic pressure of the solution, and driving force is the chemical potential gradient across the membrane. By using the external pressure greater than the osmotic pressure, the fluid will transport from the place of high solute concentration to the place of low solute concentration, and the separation of liquid from the solute is achieved. This reverse in the normal osmosis process is called reverse osmosis. Reverse osmosis or RO described also as hyperfiltration. The RO membrane pore size is less than 0.5 nm; Therefore, the main application of RO membrane is the desalination of water. As an

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example, blending of PVC polymer with different ratios of cellulose acetate to provide various kinds of RO membranes can desalinate from brackish to seawater [47, 48].

9.4.5

Pervaporation (PV)

Pervaporation (PV) is a new process used to separate mixtures of liquids. During the transport process, the liquid phase change to the vapor phase, therefore PV process is based on a solution-diffusion mechanism. PV driving force depends on the vapor pressure difference between the feed components and the permeate vapor. The maintaining of vapor pressure difference laboratory occurred by introducing permeate vacuum by using a vacuum pump. Blending PVC polymer with polyacrylonitrile provided the composite membrane with dense top layer and porous support layer of polyacrylonitrile, this membrane used for dehydration of highly concentrated acetic acid as a case of pervaporation process [49]. PVC membranes are prepared using tetrahydrofuran as the solvent can be used for separation of mixtures of binary alcohols or Benzene from cyclohexane [26, 50].

9.4.6

Membrane Distillation (MD)

Membrane Distillation (MD) is a process used in both membrane and thermal distillation. The membrane here is neither a selective barrier nor responsible for the rate transport of the components, it is an interface between two phases. The driving force is achieved by the vapor pressure difference results from the temperature difference between liquid–vapor interface [7]. Scientifically and industrially MD has a great interest because it can remove impurities from solution and produce highly pure permeate, as well as lower operating temperature. Grafted PVC with poly(ethyl acrylate) and dissolving this copolymer in dimethylformamide produced hydrophobic membrane used in vacuum membrane distillation, where the maximum permeate flux (37.5 kg/m2 h) was obtained at 60 °C with the 14 wt% PVC-g-PEA membrane [51].

9.4.7

Electrodialysis (ED)

Electrodialysis (ED) used ion-exchange membranes and the electrical field in the separation process. In case of ion exchange membrane, the charged group is attached to the material backbone of the membrane. The ions which have the same charge of the fixed charged group are partially or completely retained by the membrane, i.e., the anionic membranes which have fixed positive charge groups retained positive ions but allow the passage of negatively charged ions.

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Heterogeneous cation exchange PVC/CA blend membranes were fabricated by polymeric solution had cation exchange resin (Ion exchanger Amberlyst 15) with the treatment of prepared membrane by a solution of HCl and NaCl [52]. The produced membrane exhibited that ionic permeability and flux were initially increased with the increasing ratio of CA to 20 wt% in the polymeric solution and the membrane areal electrical resistance provided decreasing trends after cellulose acetate ratio increased in prepared PVC/CA membranes [53]. The application of PVC membrane is presented in Table 9.3.

9.5

Mathematical Model for PVC Membrane Preparation

Thermodynamics Background Thermodynamic performance is a key to the achievement of any application especially in polymeric membrane preparation depending on the phase behavior of polymers blending. The miscibility or phase separation or partial miscibility of polymers depends on the molecular weight of using polymers due to the appearance of various levels of mixing in between the boundaries [64]. The combinatorial entropy contribution is the main factor effect on the miscibility, where low molecular weight materials entropy is larger than high molecular weight polymers. Also, it is the reason that solvent–solvent mixtures offer a wider range of miscibility compared to polymer–solvent combinations. Upon the mixing of two macromolecules together the mutual immiscibility produced and the combinatorial entropy decreases in the absence of enthalpic interaction between two unlike segments [65]. Changing temperature or polymer compositions as the thermodynamic properties of the system can develop in membrane preparation using phase separation method [66]. Thus, the miscibility gap in the system at a given temperature and polymer composition will initiate the phase separation depending on the heat and mass transfer phenomena [67]. Accordingly, the miscible or immiscible of the polymer depends on the thermodynamics of polymer–polymer interactions [68, 69] and the kinetics of the mixing process [70].

9.5.1

Flory–Huggins Model for Polymeric Solution

The Flory–Huggins theory is the most common theory used in the thermodynamic analysis of mixtures of components as in a polymeric solution system. It is a mathematical model for polymeric mixtures which depends on the great dissimilarity in molecular weights of polymers according to the entropy of mixing. Mixtures of polymers are expediently divided into polymeric solutions contain one or more low molecular weight such as solvents and different polymers blends have macromolecular species. Solubility parameter, d; is the most important parameter

Ion-exchange membrane (IEM) Blend heterogeneous cation exchange membranes (CEM) Reverse osmosis (RO) Reverse osmosis (RO)

Polyvinylchloride (PVC)/ PVP

PVC/neodymium phosphate (NP) (PVC)/cellulose acetate (CA)

Ultrafiltration membranes

Ultrafiltration membranes

PVC/graphene oxide (GO)

(PVC)/polyvinyl formal (PVF) blend

Ultrafiltration membranes

Membrane distillation (MD)

PVC/ethyl acrylate (EA)

(PVC)/cellulose acetate (CA) Polyurethane/ polyvinylchloride-co-vinyl acetate (PU/PVCA) PVC/polycarbonate (PC) blend

Membrane type

Vacuum membrane distillation (VMD)

Membrane material

SEM, FTIR, tensile testing, thermogravimetric analysis (TGA) FESEM, XRD, DSC, contact angle measurement, mechanical properties, abrasion test, stability test, pure water flux SEM, FTIR, contact angle

Dry phase inversion

NIPS

Phase inversion method

NIPS methods

(FT-IR), X-ray photoelectron spectroscopy (XPS), water contact angle

Water content, contact angle, scanning optical microscopy (SOM) SEM, FTIR, and mechanical

Casting solution technique and phase inversion method Phase inversion

SEM, FTIR

(FTIR)—dispersive X-ray spectroscopy (EDX). SEM— contact angle, pore size, and porosity measurements SEM, FTIR, mechanical, porosity

Characterization methods

Sol–gel and die casting method

Phase inversion

Immersion precipitation process

Preparation method

Table 9.3 Summary of previous work for application of PVC membrane

[56]

[44]

[2]

[55]

[48]

[53]

[54]

[13]

(continued)

Water treatment, filtration of BSA solution Wastewater treatment, BSA rejection BSA rejection

Desalination

Desalination

Desalination

Desalination (salt rejection) Desalination

Ref. [51]

Application – Pure water flux

190 H. Abdallah and A. El-Gendi

PVC/PEG

PVC

PVC

PVC/zinc oxide (ZnO)— PEG 6 kDa as a pore former PVC/Pluronic F 127

PVC/acrylonitrile-methyl methacrylate (AN-MMA) PVC/hydrophilic surfactant additives: Tween-20 and Tween-80 PVC/TiO2

Preparation method

Characterization methods

Suzhou Litree Technology Co. Ltd., China Manufacturer

Hollow fiber Ultrafiltration membrane Hollow fiber Ultrafiltration membrane Hollow fiber Dry/wet-spinning technique

Litree, China Manufacturer

Phase inversion method

Phase inversion method

SEM, mechanical

SEM, AFM

SEM, dispersive X-ray analysis (EDAX), pore size and porosity, contact angle X-ray photoelectron spectroscopy (XPS), (SEM), (AFM), contact angle, and flux measurements SEM, AFM

SEM, contact angle, viscosity, porosity and pore size, mechanical properties SEM, abrasion resistance test

Immersion precipitation phase inversion method NIPS method

SEM, performance test

Performance test

SEM, EDX spectrum

Phase inversion

Manufacturer: Scottsdale Water Campus Phase inversion

Ultrafiltration membrane

Ultrafiltration membranes Ultrafiltration membranes

Ultrafiltration membrane Ultrafiltration membranes

Ultrafiltration membrane Ultrafiltration membrane

PVC

PVC/polyacrylonitrile (PAN)

Membrane type

Membrane material

Table 9.3 (continued) Application

Ref.

[61]

[60]

[39]

[29]

[2]

[29]

[59]

[58]

[57]

Rejection of [20] protein (continued)

Algal-rich water

River water

Performance test

Filtration of BSA solution BSA rejection

Wastewater treatment Treatment of anaphoretic emulsion paint Wastewater treatment Pure water, BSA

9 Preparation of Polyvinylchloride (PVC) Membranes … 191

Membrane type

TFC hollow fiber (HF) nanofiltration (NF) membranes

Low-pressure-driven nanofiltration (LPDNF) membranes

PVC/poly(methyl methacrylate-codimethylaminoethyl methacrylate) (P(MMAco-DMA))

Ultrafiltration membrane

Thin film composite (TFC) polyamide (PA)/ PVC

Membrane material

Table 9.3 (continued)

IP between piperazine and trimesoyl chloride on PVC hollow fiber substrates (Hainan Litree., Haikou, China) Non-solvent induced phase separation (NIPS)

Preparation method

X-ray photoelectron spectroscopy and SEM

FTIR—SEM—contact angle-porosity and pore size

Characterization methods

Application

Salt rejection and permeate flux

solution in deionized water Salt rejection and permeate flux

[63]

[62]

Ref.

192 H. Abdallah and A. El-Gendi

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that the polymers in many technological applications are critically dependent on it. However, the performance of prepared membranes using polymeric mixture has solvents and additives depending on the interaction of polymers with solvents and additives, that can determine the kind of produced membrane such as reverse osmosis, ultrafiltration, microfiltration, nanofiltration or others can be used in desalination, water treatment, kidney dialysis, … etc. [71]. Solubility parameter; d is used in Flory–Huggins solution theory to determine the miscibility of two polymers (i and j) by Eq. 9.1

Xij ¼

h
2 i Vr di  dj RT


di  dj gij ¼ RT

ð9:1Þ

2 ð9:2Þ

Xij; is Flory–Huggins interaction parameter depends on temperature; mole fraction of each polymer, and the degree of polymerization. Vr; is a reference volume. R; is the gas constant. d; is the solubility parameter of each component in the polymeric solution. Generally, miscibility of the polymer blend is supposed to reduce with increasing Xij. The strong interactions between two polymers blend mostly be according to hydrogen bonds found between structural units on two polymers. The model of Flory–Huggins has many modifications to facilitate using concentration and temperature-dependent interaction parameters gij especially in ternary system, where the thermo-dynamical properties can be described easily by this model at fixed temperature and pressure when concentration-dependent interaction parameters are used [66–68]. The solubility parameters can be determined by calculation of the cohesive energy of materials. The cohesive energy, E; means that the increasing in the internal energy per mole of the component if all of the intermolecular forces are eliminated. The energy required to break all intermolecular physical links in a unit volume of the material is called the cohesive energy density (CED) [64, 71]. CED ¼

E V

E ¼ DHv  RT

ð9:3Þ ð9:4Þ

where, DHv; is the enthalpy of vaporization. The Hildebrand solubility parameter is determined as the square root of the cohesive energy density: d¼

pffiffiffiffiffiffiffiffiffiffi CED

rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ðDHv  RT Þ d¼ V

ð9:5Þ ð9:6Þ

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The Hildebrand solubility parameters depend on the hydrogen bond especially at materials with similar polarities, where the solubility of them is very high. Three specific molecular interactions to develop solubility parameters [42, 71]: • The first one is dispersive interactions (non-polar), that depends on the forces occur due to negatively charged electrons orbiting around a central positively charged nucleus of each atom, where the motion of charges provides an electromagnetic field show the way to the attraction of the atoms to one another regardless of direction [42]. This attraction is found in all molecules. • Polar cohesive forces are the second type of interaction produced by enduring dipole–dipole interactions. These forces have a correlation between dipole moment of the molecule with the contribution to the dipole moment [64, 71]. These intrinsically molecular interactions are found in the most molecules to the one extent or another. • A hydrogen bond is considered the third type of interaction and these bonds are weaker than covalent bonds but are much stronger than ordinary dipole–dipole interactions. Accordingly, the total cohesive energy can be calculated corresponding to the three types of interactions [42, 71]: E ¼ ED þ EP þ EH

ð9:7Þ

Also, the total square of the Hildebrand solubility parameter can be calculated by dividing the cohesive energy by the molar volume as the sum of the squares of the Hansen dispersion (D), polar (P), and hydrogen bonding (H) components: d2 ¼ d2D þ d2P þ d2H

ð9:8Þ

The solubility of any polymer in various solvents is largely determined by the chemical structure of this polymer. Free energy of mixing controls the dissolution of an amorphous polymer in a solvent [71, 72]. DGm ¼ DHm  TDSm

ð9:9Þ

DGm is a free energy of mixing, DHm is an enthalpy change or (heat of mixing) and DSm is an entropy change of mixing. DGm must be smaller than zero to provide miscibility of the mixture. Increasing temperature leads to increase in the miscibility for low molecular weight materials. If TDSm term increases, DGm has negative value. Higher molecular weight components provide a small term of TDSm, also the other factors such as non-combinatorial entropy contributions and temperature according to DHm values can dominate and guide to the reverse behavior, means, decreasing miscibility with increasing temperature. Accordingly, a very small positive entropy change means the dissolution of a high molecular weight polymer happens, but the crucial factor in determining the sign of the Gibbs free energy change is the enthalpy change term [71].

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The homogeneity of the polymer blends miscibility depends on the molecular structure, where the domain size is similar to the macromolecular dimension that provided the negative value of the free energy of mixing, DGm  DHm  0, and within the phase stability condition ∂2DG/∂2/ > 0. Immiscible of polymer blends will occur when the free energy increases upon mixing, by the mean DG  DH > 0. The important term of the polymer blend is compatibilization, that means the modification process for the interphase of immiscible polymer blends, leads to a reduction in the interfacial energy, development, and stabilization of a needed morphology, which leads to the formation of a new polymer alloy with improved performance. The most relevant theory for mathematical modeling for polymer blends which is employed for solvent–solvent and polymer–solvent mixtures was independently derived by Flory [67, 68] and Huggins [69, 70]. The key equation of this model for binary systems is [1, 2]: DGm ¼ RTV½/1 =v1 ln/1 þ /2 =v2 ln/2 þ ð/1 /2 X1 2Þ=vr 

ð9:10Þ

where, V; is total volume, R; is gas constant, ui; is volume fraction of component i, Vi; is molecular volume, vi; is the molar volume of polymer chain i, or; is molecular or molar volume of a specific segment, X12; is Flory–Huggins interaction parameter. vr can be calculated as the square root of the product of the individual segmental unit molecular or molar volumes of the polymeric components as shown in Eq. 9.11. vr ¼

pffiffiffiffiffiffiffiffiffi v1 v2

ð9:11Þ

The general expression of the model was modified and extended for a model of ternary and quaternary polymer solutions to be. For ternary solutions: ðDGm Þ=RT ¼ n1 ln/1 þ n2 ln/2 þ n3 ln/3 þ ðv1 Þn1 /2 g1 2 þ ðv1 Þn1 /3 g1 3 þ ðv2 Þn2 /3 g2 3

ð9:12Þ For quaternary solutions: X X DGm ¼ RT½ ði ¼ 1; 2; 3; 4Þni  ln/i þ n1  /2  X12 þ n1 ði X X X ¼ 1; 2; 3Þ/i ði ¼ 1; j ¼ 2; 3; 4ÞXij þ n2 ði ¼ 3; 4Þ/i ði ¼ 2; j X X ¼ 3; 4ÞXij þ n3 ði ¼ 4Þ/i ði ¼ 3; j ¼ 4ÞXij  ð9:13Þ

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where; ni is a number of moles of component i (mole). /i is a volume fraction of component i. A mathematical model for ternary polymeric solution system consists of three components, like a case of solvent which is low molecular weight component as (NMP), and two high molecular weight polymers such as polyvinylchloride (PVC) and Cellulose acetate (CA). Polymer gel formation occurs depending on two separate interfaces. One of them is the glassy polymer and the gel layer and the other is between the gel layer and the solvent and after a certain time, the polymeric solution has complete solubility [67, 72]. The free energy of mixing controls this process. However, the free energy has a negative value, which means mixing of polymeric solution can occur impulsively. Using a high molecular weight polymer in a mixture means the dissolution of it will be with a very small positive entropy change. However, enthalpy term is the effect of the sign of the Gibbs free energy change. Increasing in polymers concentration provides reduce in dissolution rate and increase mixing time also the solubility parameters must be taken into consideration. Polymeric solution temperatures effect on the Gibbs free energy of mixing and chemical potential for each component, as shown in Fig. 9.6. Where, DGm  DHm  0 in the phase stability condition, providing negative value of DGm and (ϐ2DGm/ϐ2u) > 0, due to no limitation of the miscibility for two minimum compositions, while the constant line explains the phase separation of polymers in the mixtures doesn’t occur during mixing of these blend polymer (PVC/ CA) for all compositions [71, 72]. In case of the quaternary polymeric solution, the system has four components, thermodynamic model using two mixed solvents N-methyl-2-pyrrolidone (NMP) and tetrahydrofuran (THF) with two high molecular weight polymers cellulose acetate (CA) and polyvinylchloride (PVC) was studied by Abdallah et al. [73]. Figure 9.7a illustrates that the Gibbs free energy is approximately constant using low volume fraction of CA depending on polymeric solution homogeneity and due to the negative value of the free energy of mixing, DGm  DHm  0

deltaG Chem Pot

ϕP1

Δμ

ΔG

Fig. 9.6 DG and l as a function of volume fraction of the main polymer at room temperature [72]

9 Preparation of Polyvinylchloride (PVC) Membranes …

197

within phase stability condition (ϐ2DGm/ϐ2u) > 0. However, in case of the sspolymeric solution of PVC with using PVP (polyvinyl pyrrolidone) as a pore former, the Gibbs free energy varies slightly in this volume fraction of PVC. According to that the polymer and the additive have no limitation of miscibility and the solution was homogeneous as shown in Fig. 9.7b. For ternary polymer solutions, chemical potential for three components is calculated to draw the ternary coexistence curve. Chemical potential can be calculated by taking the first derivative of the free energy of mixing according to the mole fraction of each component using Eqs. 9.14, 9.15 and 9.16. Equations 9.17 and 9.18 indicate the independent factor of the Flory–Huggins model gij. The pseudo-binary compositions are exhibited in a different notation as in Eqs. 9.19 and 9.20 [68, 70].

Fig. 9.7 DG as a function of volume fraction at various temperatures, a DG as a function of /CA and b DG as a function of /PVC [73]

-150 -200 -250

ΔG

-300 -350 T=313K T=323K T=333K T=363K

-400 -450 -500

0

0.02

0.04

0.06 0.08 ϕCA

0.1

0.12

0.14

(a) -300 -350 -400

ΔG

-450 -500 -550

T=313K T=323K T=333K T=363K

-600 -650 -700 0.08

0.09

0.1

0.11 0.12 ϕPVC

(b)

0.13

0.14

0.15

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ðDl1 Þ=ððv1 ÞRTÞ ¼ ðln/1 Þ=ðv1 Þ  /1 =ðv1 Þ  /2 =ðv2 Þ  /3 =ðv3 Þ þ 1=ðv1 Þ þ ðg12/2 þ g13/3 Þð1  /1 Þ  g23/2 /3  g120 /2 ð9:14Þ ðDl2 Þ=ððv2 ÞRTÞ ¼ ðln/2 Þ=ðv2 Þ  /1 =ðv1 Þ  /2 =ðv2 Þ  /3 =ðv3 Þ þ 1=ðv2 þ ðg12/1 þ g23/3 Þð1  /2 Þ  g13/1 /3  g230 /3 ð9:15Þ ðDl3 Þ=ððv3 ÞRTÞ ¼ ðln/3 Þ=ðv3 Þ  /1 =ðv1 Þ  /2 =ðv2 Þ  /3 =ðv3 Þ þ 1=ðv3 Þ þ ðg13/1 þ g23/2 Þð1  /3 Þ  g12/1 /2  g230 /2 ð9:16Þ 0

dg12 du2

ð9:17Þ

0

dg23 dv2

ð9:18Þ

g12 ¼ u2 ð1  u2 Þ g23 ¼ v2 ð1  v2 Þ

ui ¼ /i =ð/i þ /1 Þ

ð9:19Þ

vi ¼ /i =ð/i þ /2 Þ

ð9:20Þ

where: Dli DGm /i ni

is the change in chemical potential of component I (J/mol). Change in Gibbs free energy of the mixture (J/mol). Volume fraction of component i. Number of moles of component I (mole).

While for Chemical potential, of components: 1-polymer (1), 2-polymer (2), 3-solvent (1), and 4-solvent (2), is used for calculating and drawing quaternary coexistence curve. It is calculated by taking the first derivative of the Gibbs free energy of mixing equation with respect to the mole fraction of each component, Eqs. 9.21–9.24.       Dl1 @X12 @X23 @X24 ¼ a þ bð1  /1 Þ  c  /2 u2 ð1  u2 Þ  /3 u3 ð1  u3 Þ  /4 u4 ð1  u4 Þ RT @u2 @u3 @u4

ð9:21Þ       sDl2 @X12 @X23 @X24 ¼ d þ eð1  /2 Þ  f  /1 u2 ð/1  u2 Þ  s/3 v3 ð1  v3 Þ  s/4 v4 ð1  v4 Þ RT @u2 @v3 @v4

ð9:22Þ

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199

      rDl3 @X13 @X23 @X34 ¼ g þ hð1  /3 Þ  k þ /1 u3 ð1  u3 Þ þ s/2 v3 ð1  v3 Þ þ r/4 w4 ð1  w4 Þ RT @u3 @v3 @w4

ð9:23Þ       tDl4 @X14 @X24 @X34 ¼ l þ mð1  /4 Þ  q þ /1 u4 ð1  u4 Þ þ s/2 v4 ð1  v4 Þ þ r/3 w4 ð1  w4 Þ RT @u4 @v4 @w4

ð9:24Þ The ratio between the various molar volumes Vi is illustrated in the variables; s, r and t. In addition, variables a, b, c, d, e, f, g, h, k, l, m and q are used to simplify the appearance of the formula in Table 9.4: s¼

V1 V2

ð9:25Þ

r¼

V1 V3

ð9:26Þ

t¼

V1 V4

ð9:27Þ

The pseudo-binary compositions are calculated using the following equations:

Table 9.4 Simplified variables list

ui ¼ /i =ð/i þ /1 Þ

ð9:28Þ

vi ¼ /i =ð/i þ /2 Þ

ð9:29Þ

wi ¼ /i =ð/i þ /3 Þ

ð9:30Þ

Variables

Related equation

A B C D E f g h k l m q

ln/1  s/2  r/3  t/4 1 þ X1 2/2 þ X1 3/3 þ X1 4/4 sX2 3/2 /3 þ sX2 4/2 /4 þ rX3 4/3 /4 ln/2  /1  r/3  t/4 s þ X1 2/1 þ sX2 3/3 þ sX2 4/4 X1 3/1 /3 þ X1 4/1 /4 þ rX3 4/3 /4 ln/3  /1  s/2  t/4 r þ X1 3/1 þ sX2 3/2 þ rX3 4/4 X1 2/1 /2 þ X1 4/1 /4 þ rX2 4/2 /4 X1 2/1 /2 þ X1 4/1 /4 þ rX2 4/2 /4 t þ X1 4/1 þ sX2 4/2 þ rX3 4/3 X1 2/1 /2 þ X1 3/1 /3 þ sX2 3/2 /3

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Figure 9.8a indicates that during mixing of polymeric solution from CA and PVC the chemical potential of CA at various temperatures decreases by increasing the composition of CA, that can lead to problems in blending between two polymers when the composition of CA increases. While, in case of using another polymer such as PVP the decreasing of chemical potential of PVC at various temperatures of polymer solution from PVP and PVC, that means complete mixing between PVP additive with PVC polymer in two solvents THF and NMP as shown in Fig. 9.8b.

-3.0E+06

Fig. 9.8 Chemical potential as a function of volume fraction at different temperatures, a lCA as a function of /CA and b lPVC as a function of /PVC [73]

T=313K T=323K T=333K T=363K

-3.1E+06 -3.2E+06 μCA

-3.3E+06 -3.4E+06 -3.5E+06 -3.6E+06 -3.7E+06

0

0.02 0.04 0.06 0.08 0.1 0.12 0.14 ϕCA

μPVC

(a) -6.0E+06 T=313K -6.2E+06 T=323K -6.4E+06 T=333K -6.6E+06 T=363 -6.8E+06 -7.0E+06 -7.2E+06 -7.4E+06 -7.6E+06 -7.8E+06 -8.0E+06 0.08 0.09 0.1 0.11 0.12 0.13 0.14 0.15 0.16 ϕPVC

(b)

9 Preparation of Polyvinylchloride (PVC) Membranes …

9.5.2

201

Diffusion Model of Immersion Precipitation

The membrane formation by immersion precipitation is expressed by many researchers model [67–78], which can describe the diffusion process during formation of a thin film polymer solution (formed membrane) in a gelation bath containing non-solvent (water) with a sequence of assumptions which are important to mention, Fig. 9.9: 1. The center of the interface can be selected to be a reference system between casting membrane on a glass plate and the coagulation bath. 2. The interface of the formed membrane in the bath has an initial composition as the original coagulation bath. 3. The membrane polymer film is considered as a matrix phase; accordingly, the low molecular weight components diffuse. 4. The volume of the polymeric solution on the glass plate is not constant. 5. One phase system is assumed depending on the diffusion path of solvent from polymer film until the spinodal reach. 6. Spinodal will be reached due to diffusion of solvent from polymer film to the coagulation bath. 7. The mobility of the high molecular weight components (polymer) is slower than the low molecular weight components. 8. The fluxes of components in diffusion process are independent of the formed membrane thickness. Equation 9.31 is used to explain the formula which describes diffusion in the polymer solution, where, component (i) illustrates polymer components.

Fig. 9.9 Schematic representation of the reference system to represent diffusion in the immersion precipitation process [73]

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  d

/i /n

dt

@ ¼ vi @m

(

X

/lj /n Lij @m j¼1:n1

) ð9:31Þ

where the coordinate transformation from the Cartesian reference system (x) to the polymer fixed reference system (m) can circumvent the volume of polymer change penalty. (x) in the polymer solution is converted in a polymer fixed reference system (m) and a reference system originating from the interface between polymer solution and coagulation bath (y) as shown in Fig. 9.9. The transformation is given by Eqs. 9.32 and 9.33: ZL m¼

/i dx

ð9:32Þ

y ¼ x  Dx

ð9:33Þ

0

where; L Total film thickness (m). Equation 9.34 indicates the diffusion of solvent during immersion process in the coagulation bath, where component (j) represents solvent. d/i @ ¼ vi @y dt

(

X

@lj Lij @y j¼1:n1 0

) 

@/i X Jk @y k¼1:n1

ð9:34Þ

where: i = 1: n − 1. t Time (s). vi Molar volume of component i (m3/mol). Jk Flux of species k into the coagulation bath at the interface between polymer solution and coagulation bath at (y = 0). 0

Lij and Lij are the matrix elements of the phenomenological coefficient matrix L 0

0

and L respectively. L and L are the inverse of the friction coefficient matrix R and 0 0 R respectively. The R and R can be calculated according to the following equations: X Ri i ¼ ð ðk 6¼ iÞck Ri kðRTðvi ÞÞ=ðMi Di kÞ þ cn ðRTðvi ÞÞ=ðMi Di nÞÞ ð9:35Þ 0

Rii ¼ 

X k6¼i

ck

RTvi Mi Dik

ð9:36Þ

9 Preparation of Polyvinylchloride (PVC) Membranes …

Rij ¼ cj 0

Rij ¼ cj

203

RTvi Mi Dij

for i 6¼ j

ð9:37Þ

RTvi Mi Dij

for i 6¼ j

ð9:38Þ

where: Dij R T Mi

Binary diffusion coefficient between i and j (m2/s). Universal gas constant (J/mol/K). Temperature (K). Molecular weight of component i (kg/kmol).

Initial Conditions The initial conditions for the polymer solutions and the coagulation bath are shown below, respectively: /i ðm; t ¼ 0Þ ¼ /ði; PolymersolutionÞ /i ðy; t ¼ 0Þ ¼ /ði; CoagulationbathÞ Boundary Conditions The boundary conditions for the polymer solutions and the coagulation bath are shown below, respectively: dð/i Þ ¼0 dt

for m ¼ 1

dð/i Þ ¼0 dt

for y ¼ 1

An additional requirement is that the fluxes and chemical potentials of different components are equal at both sides of the interface: Dlðm ¼ 0Þ ¼ Dlðy ¼ 0Þ for i ¼ 1: n  1 J i ð m ¼ 0Þ ¼ J i ð y ¼ 0Þ

for i ¼ 1: n  1

The effect of time during immersion precipitation process in the coagulation bath can be explained by solvent separation from the polymer solution by dissolving in the water bath. Where during the time the solvent concentration will increase in the bath providing phase separation process, where the polymer blend which contains high polymer concentration has been formed after solvent separation from polymer solution to coagulation bath to form membrane film, the model of the immersion precipitation is illustrated by Eqs. 9.31, 9.32, 9.33 and 9.34.

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Figure 9.10 shows the change in /polymer//solvent and /polymer during the formation process of the membrane as a function of time. The ratios of /P1//S and /P2//S increase due to coagulation process of the membrane and the polymer content increased and concentrated in the body of the membrane, while the solvent content outflows to the coagulation bath. Figure 9.10 illustrates the volume fraction of polymers in the coagulation bath (water). The volume fractions of polymer blend at the interface inside the coagulation bath are equal to the volume fraction at the beginning of the formation of the membrane. The polymer concentration will reduce in the water bath, while the solvent concentration will increase as a result of the separation of polymer material in the membrane during formation. However, the model indicates that the volume fraction of solvent increases in the water of coagulation bath. On the other hand, the volume fraction of polymer solution decreases with time; leading to the formation of coagulated polymer blend to form blend P1/P2 membrane as shown in 3DMATLAB surface solution with different initial concentrations, Fig. 9.11a, b. Figure 9.11a illustrates that the thickness of polymers increases with time due to the membrane formation, while the thickness can reach to around 225 lm after 500 min that also depends on the amount of polymer solution and the wet casting thickness. However, Fig. 9.11b illustrates that the diffusion of the polymer solution in the coagulation bath reduces with time due to the coagulation of polymer solution and outflow of solvent from the polymer solution to the bath [67–73]. Figure 9.12a shows the formed membrane structure after 500 min in the coagulation bath which indicates that the upper selective layer was formed from CA and the middle and bottom layer from PVC and the formed membrane thickness was 284 µm. By comparing the predicted composition with composition from experimental work, a similar shape of membrane cross-section was produced, where the dense top layer was CA and the bottom layer was PVC as shown in Fig. 9.12b.

Phi P2/ Phi S Phi P2

ϕpolymer

ϕPolymer/ϕsolvent

Fig. 9.10 /polymer//solvent and /polymer as a function of time [68]

Time, min

9 Preparation of Polyvinylchloride (PVC) Membranes …

205

Phi P/Phi S

400

300

200

100

0 1500 250

1000

200

Tim 500 e, m in

150 100 0

50 0

(a)

s k nes Thic

eter ic rom m , m

0.4

Phi P

0.3

0.2

0.1

0 1500 4

1000

Tim e, m 500 in

3 2 1 0

0

(b)

x nc e Dis ta

, in m

4

x 10

et er ic rom

Fig. 9.11 a /P//S as a function of time and thickness of membrane at T = 298 K, and b /P2 as a function of time [69]

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100% 80% 60% 40%

CA PVC

20% 0%

1 2 3 4 5 6 7 8 9 10 11 12 13 Membrane Thickness=284 μm

(a)

(b)

Fig. 9.12 a Representation of model solution of membrane constituents after 500 min of coagulation and b electron scan of blend membrane PVC/CA [73]

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55.

56.

57.

58. 59.

60.

61. 62.

63.

64. 65. 66. 67. 68. 69. 70. 71. 72. 73.

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76. Bouyera D, Weapon W, Pochat-Bohatiera C, Deratani A (2010) Morphological properties of membranes fabricated by VIPS process using PEI/NMP/water system: SEM analysis and mass transfer modeling. J Membr Sci 349:97–112 77. Khare VP, Greenberg AR, Krantz WB (2005) Vapor-induced phase separation effect of the humid air exposure step on membrane morphology Part I. Insights from mathematical modeling. J Membr Sci 258:140–156 78. Krantz WB, Greenberg AR, Hellman DJ (2010) Dry-casting: computer simulation, sensitivity analysis, experimental and phenomenological model studies. J Membr Sci 354:178–188

Chapter 10

Bio-Based Polyvinylchloride (PVC)-Related Blends Raluca Nicoleta Darie-Nita, Maria Râpă, and P. M. Visakh

Abstract Despite the fact that PVC is one of the most useful materials available to the plastic market, with properties as strong, durable, versatile and lightweight, low cost and chemical resistance, its inadequate disposal has contributed to strong noneconomic issues based on the negative effects of chlorine. The use of biodegradable polymers and their mixtures is an important solution for decreasing the environmental pollution caused by disposal of PVC non-degradable waste. Since sustainable chemistry and engineering require the production of materials and technologies based on degradable polymers, this chapter presents some possibilities of blending PVC with biodegradable additives and/or of natural origin, as well as their production techniques, enhancing the changes in the resulting properties. Blends of PVC with nanofillers, degradable polyesters (polyhydroxyalkanoates and poly(e-caprolactone)), polysaccharides (cellulose, starch, chitin, chitosan), natural fibers (derived from plants or wood), protein (collagen) and poly(vinyl alcohol) are some examples of PVC bio-related blends discussed in this chapter.








Keywords Polyvinylchloride (PVC) Natural fillers Nanocomposites Degradability Processing methods Physico-mechanical properties







R. N. Darie-Nita (&) Physical Chemistry of Polymers Department, “Petru Poni” Institute of Macromolecular Chemistry, 41A Gr. Ghica Voda Alley, Iași, Romania M. Râpă Centre for Research and Eco—Metallurgical Expertise, University Politehnica From Bucharest, 313 Splaiul Independentei, 060042 Bucharest, Romania P. M. Visakh Department of Physical Electronics, TUSUR University, Tomsk, Russia © Springer Nature Switzerland AG 2022 V. P. M. and R. N. Darie-Nita (eds.), Polyvinylchloride-based Blends, Springer Series on Polymer and Composite Materials, https://doi.org/10.1007/978-3-030-78455-3_10

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Introduction

Polyvinylchloride (PVC) is the second-largest thermoplastic commodity produced worldwide after polyethylene [1]. It is less costly when compared to other polymers, such as: ABS, LDPE and HDPE [2] and metals (i.e., aluminum powder, iron powder and magnesium). The global demand for PVC exceeded 30 million metric tons in 2009, and it is in constant growth (+5% on global average), especially in developing countries (http://www.pvc.org/en/). PVC shows excellent properties in terms of hardness, chemical resistance, lightweight, flame retardation and flexibility making PVC as an ideal candidate material for applications, such as: windows, tubes, pipes, cables and wires and fittings, sport articles and packaging. PVC is also used in biomedical applications, especially as a catheter material for the circulatory system [3]. An increasing interest in developing PVC-based materials with self-sterilizing and antibacterial properties appeared during last years in order to solve some serious issues in healthcare-associated infection like microbial colonization of medical device surfaces and the subsequent biofilm formation. Different types of PVC nanocomposites containing metals or metal oxides were proposed [4], but efforts were also turned to find natural antibacterial materials that could be easily incorporated in the PVC by the common techniques [5]. Among other commodity polymers, PVC materials present some drawbacks due to the use of non-renewable chemicals and non-biodegradable waste materials. Its poor thermal stability, stiffness and brittleness could be improved by compounding PVC with additives, such as heat stabilizers, plasticizers and impact modifiers. Despite the fact that PVC is one of the most useful materials available to the plastic market, its inadequate disposal has contributed to strong noneconomic issues based on the negative effects of chlorine. Ethylene and chlorine are the two main feedstocks needed to manufacture PVC. Due to concerns regarding the petroleum resources, environmental pollution and release of carbon footprints into the atmosphere, the new bio-PVC materials became interesting among researchers and industrial. Thus, bio-ethanol is considered a replacement source for ethylene in the bio-PVC production chain [6]. The studies revealed that bio-PVC material presents lower environmental impacts than fossil-based PVC. The use of ethylene partially derived from sugarcane and the chlorine content derived from brine could be a new route for production of bio-PVC, according to Solvay Indupa Company [7]. A plant of 120 kilo tons per year of bio-PVC capacity was envisioned with keeping in mind Latin America as the initial target market. However, due to the recent announcement of an increase in the costs of bio-polyethylene by Braskem, it gave rise to the uncertainty of starting the project. The use of biodegradable polymers and their mixtures is an important solution for decreasing the environmental pollution caused by disposal of PVC waste. Investments in research to develop bioproducts are likely to open up opportunities for PVC market growth.

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Materials with advantageous properties that may be successfully used in construction or in the automotive and furniture industries could be PVC biocomposites with different types of fillers resulted from renewable materials, such as wood fiber and lignin [8, 9], or natural plant fibers such as jute, bamboo, sisal and rice straw [10, 11]. The natural origin of the filler, its particle size and its aspect ratio, as well as its concentration and the homogeneity of its distribution in the polymer matrix, are important factors affecting the properties of PVC biocomposites [12]. Natural reinforcements have advantages over synthetic reinforcements as a result of the natural alignment of the carbon–carbon bonds and also its significant strength, stiffness, low density, low cost and biodegradability [13]. Since sustainable chemistry and engineering require the production of materials based on degradable polymers and development of technologies for their processing, this chapter presents some possibilities of blending PVC with natural additives, their characteristics and the future application for market.

10.2

PVC Bio-Related Nanoblends

Depending on the nanofiller type, the nanocomposites present several improved properties, namely: enhancement of the thermal, mechanical and barrier properties by increasing path length for gas diffusion and changes in surface wettability and hydrophobicity [14]. Among the most used nanofillers and nanoreinforcements, several should be mentioned: clay montmorillonite (MMT), kaolinite and silicate nanoplatelets, silica nanoparticles, carbon nanotubes, graphene nanosheets, silver, zinc oxide, titanium dioxide, copper and copper oxides, starch nanocrystals, cellulose nanofibers and nanowhiskers, chitosan and chitin whiskers and others. Mohamed A. T. showed that the dielectric properties of PVC cable insulation have a close relationship with the interfacial behavior between the nanofillers and the polymer matrix in such nanocomposites [15]. The solgel processing of the nanoparticles inside the polymer is the ideal procedure for the formation of interpenetrating networks between nano-clay and PVC at the milder temperature leading to enhance the compatibility and interfacial interaction between two phases. It was found that the electric resistivity of PVC/clay nanocomposites (up to 10 wt% clay) increased from 1013 Xm in the case of pure PVC to 1017–1020 Xm in the case of PVC/clay 10 wt% nanocomposite. Adding 1 wt% clay into PVC matrix decreased real relative permittivity, specially, at higher frequencies. The real relative permittivity increased with increasing thermal temperatures, specially, at low frequencies; then, increasing clay nanoparticles more than 1 wt% increased real relative permittivity gradually. PVC bionanocomposites can be also produced by using nanoelements resulted from different renewable resources, e.g., cellulose, starch, chitin [16]. Many researches are dedicated to cellulose whiskers as it is the polymer most abundant on Earth. As nanoparticles have a strong tendency to agglomerate, appropriate

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processing should be selected to obtain homogeneous dispersion of nanoparticles in the matrix. Cellulose nanocrystals characterized by high aspect ratio and a large interface area were used as reinforcing materials in PVC matrix. Blending PVC with biodegradable cellulose derivative is intended also to thermally support the polymer during the molding process, as well as to enhance the biodegradability of PVC waste products. Biodegradable nanocomposites of PVC and nanocellulose whiskers (in content of 0.1, 0.5, 1, 3, 5, 8%) isolated from rice straw were prepared by melt mixing [16]. TEM results showed a good dispersion of nanocellulose particles in PVC, with the size range of nanocrystals from 44 to 66 nm. Significant improvements of elongation at break and tensile strength were observed as a result of addition of nanoparticles to the PVC matrix especially at low nanoparticles loading (1%) due to strong interaction between nanocellulose fiber and matrix caused by large interfacial areas. It was found that nanoparticles above 1% content in PVC matrix led to decreased mechanical properties as the result of the aggregation effect of nanoparticles. Thermogravimetric analysis (TGA) of PVC/cellulose nanocomposites showed slightly lower onset degradation temperature (  250 °C) than neat PVC. The biodegradation of the PVC/nanocellulose composites increased with increase in the nanocellulose amount in the nanocomposites. Different theoretical predictions were proposed by Chazeau et al. [17] to describe the viscoelastic properties of PVC/cellulose whisker nanocomposite (up to 12.4 vol % filler) above and below its glass transition temperature (Tg). The small discrepancy between a model based on the Halpin–Kardos equation and the experimental modulus measured by dynamic mechanical analysis in the rubber plateau is discussed as a possible effect of a percolating whisker network whose cross-links are assured by chains adsorbed onto the whisker surface. A novel strategy has been published on producing organic and biodegradable nano-bioplastic (nanobiofilm) from corn leaf biomass by bioprocess technology without chemicals [18]. Acetic acid, PVC, starch powder and water were mixed with cellulose samples, followed by subsequent blending with PVC/glycerin. Pyrolysis method was applied until visual plasticity occurred in the oven for nano-bioplastic film material. The completely dried nano-bioplastic film showed negligible water absorbed, no odor, yellow–orange flame and slow speed of burning, while color dying, tensile properties, pH, cellulose content, shape and firmness followed the American Standard for Testing and Materials (ASTM). An Ag/chitosan (CS)-PVC nanomaterial with good biocompatibility and high antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, intended to be used as self-sterilizing catheter biomaterial especially for the cardiovascular system, has been developed by Dwivedi et al. [3]. SEM images show Ag nanoparticles dispersed in the homogeneous CS-PVC copolymer matrix with minimum aggregation explained by the interaction between the pair of electrons present at the amine groups of CS and the partial positive charge developed at the surface of the silver nanoparticles due to electron drift, which stabilizes the silver nanoparticles.

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New ternary nanocomposite systems containing PVC, chitosan-modified ZnO (CMZN) nanoparticles and new synthesized polyamide (PA) were prepared by solution casting method in an attempt to improve the PVC stability against de-hydro chlorination and eventually thermal stability [19]. The XRD pattern results revealed an acceptable distribution of ZnO nanoparticles and compatibility of PA in the PVC matrix. Thermal properties of PVC/ZnO–PA nanocomposites have been improved compared to the neat PVC. PA and CMZN have had good synergistic effect to improve the tensile strength and Young’s modulus properties of PVC. The results from Congo red tests exhibited a delay in the HCl release processing from PVC/ ZnO–PA nanocomposites compared to the neat PVC. The combustion properties of the all PVC systems were investigated by microscale combustion calorimeter (MCC). It was found that in the presence of CMZN, synthesized PA exhibited good synergistic effect to decrease peak heat release rate, the total heat release and the heat release capacity of the PVC nanocomposites. Innovative, functional, “green” and relatively cheap PVC filler was proposed in the form of an advanced SiO2-lignin hybrid material [10]. Amounts of 2.5, 5, 7.5 and 10 wt% of the amorphous silica, lignin and silica–lignin hybrid filler were introduced into the PVC matrix by melt mixing, resulting in composites with homogeneous structure and positive processing and functional properties, especially thermal stability and Vicat softening temperature. The microscopical analysis (optical and SEM) showed well-dispersed silica particles in the matrix polymer with a reduced tendency to aggregation for PVC/silica blends, while PVC/lignin system is characterized by a worse homogeneity with non-uniform agglomerations. When using SiO2-lignin combination as filler, particles of the silica–lignin hybrid filler are visible with good adhesion within PVC matrix. b-cyclodextrin (b-CD) is a cyclic oligosaccharide resulted from the enzymatic degradation of starch. Several studies showed that (b-CD) derivatives reduced the migration of di(2-ethylhexyl) phthalate (DEHP), probably due to the complexation of b-CD with DEHP via host–guest interaction [20]. An innovative nano-inhibitor was synthesized by grafting a cross-linked poly(b-cyclodextrin-ester) to Fe3O4 nanoparticles (MNP-CDP) and further incorporated to PVC (PVC/DMCPs) by ultrasonic technique—Fig. 10.1 [21]. Initially, poly(b-cyclodextrin-ester) network (b-CDP) was synthesized via reaction of b-cyclodextrin with 3,3′,4,4′-benzophenone tetracarboxylic dianhydride. Different amounts of PVC (54.6, 53.8 and 53 wt %), DMCPs, epoxidized soybean oil (ESO) (3 wt%) and a thermal stabilizer (2 wt %) were used to prepare plasticized PVC by solvent casting method. Following a complex investigation, the new nano-inhibitors were found to be effective on reducing the DEHP migration from studied PVC samples (about 65%), without affecting the mechanical and thermal properties of plasticized PVC. A better dispersion of nanoparticles was found when 0.4 and 1.2 wt% of MNP-CDP were incorporated into PVC matrix, and strong interaction with PVC matrix leads to better arrangement of the polymer chains.

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Fig. 10.1 Illustration of plasticized PVC films containing MNP-CDP nanoparticles (PVC/ DMCPs). Reprinted from [21] Copyright © 2017 with permission from Elsevier

10.3

PVC/Polyester Bio-Related Blends

Biopolyesters were investigated for the plasticizing and thermal effects in PVC.

10.3.1 PVC/Polyhydroxyalkanoate (PHA) Blends Due to the presence of high number of polar, as well as nonpolar groups in PHA, this polyester of bacterial origin has potential to be a natural-based plasticizer for PVC. By adding biodegradable components in PVC matrix, environmentally friendly materials were produced. From another point of view, as PHAs are biodegradable polymers, their blending with PVC might raise a concern of accelerating the loss of properties essential for durable PVC applications, especially in conditions supporting microbial activity.

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New renewable and very efficient multifunctional bio-based PHA modifiers for PVC have been developed at Metabolix Inc. (Massachusetts, USA). These three copolymers: I6001, a semicrystalline polyhydroxybutyrate (PHB) copolymer; I6002, an amorphous PHB copolymer; and a developmental, next-generation PHA grade for rigid PVC offer toughening, plasticization, good UV stability, transparency and improved processing of all types of PVC compounds. They can be added to PVC matrix up to 40 phr, present no processing problems and also significantly improve the mechanical and environmental performance characteristics of PVC (https://www.ptonline.com/articles/modifying-pvc-with-bio-based-pharubber [22]). PVC was used as an additive to crystalline polyhydroxybutyrate valerate (PHBV) to improve PHBV’s mechanical and processing properties, depending on the hydroxyvalerate (HV) content [23]. Miscible blends were obtained with PHB-HV containing 18% HV (PHB-18HV) and PVC, with a single Tg in the whole range of compositions, while blending PHB-HV containing 8% HV (PHB-8HV) with PVC, immiscibility was demonstrated by two separate Tg values in all compositions (Fig. 10.2). Tensile strength and Young’s modulus increased with increasing PVC component, except for elongation at break. The plasticizing effect in PVC of the polymeric and oligomeric medium chain length poly(3-hydroxyalkanoates) (mcl-PHAs) has been evaluated by Sin et al. [24]. mcl-PHA was synthesized by Pseudomonas putida PGA1 from two different carbon substrates: oleic acid (OA) and saponified palm kernel oil (SPKO). Compatibility of mcl-PHA with PVC was proven by a single Tg with lower values than PVC. This good miscibility could be explained by the presence of polar groups in PHA that could have dipole-induced dipole interaction with the PVC, while the long chains of nonpolar pendant groups in PHA can cause reduction in polar forces between the PVC chains, thus allowing the chains to glide past each other more easily. An increased amount of the PHA decreased the Tg of the blends. A lower plasticizing role for PVC has been recorded when using oleic acid-derived

Fig. 10.2 Dynamic loss modulus (E″) curves of various PHB-8HV/PVC blends: (open circle) pure PHB-PHV, (open triangle) 70:30 wt% PHB-8HV/PVC, (open square) 50/50, (filled circle) 30/70 and (filled square) pure PVC. Reprinted from [23] Copyright © 1995 with permission from Elsevier

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mcl-PHA, in either polymeric or oligomeric form, by reducing the Tg of the polymer blends less effectively, compared to SPKO-derived mcl-PHA. PHA copolymers could be considered as renewable and very efficient modifiers for plasticization, impact modification and processing of semirigid and flexible PVC.

10.3.2 PVC/Poly(e-Caprolactone) (PCL) Blends In order to facilitate its biodegradation, PVC can be blended also with biodegradable and biocompatible aliphatic polymers. The aliphatic polyesters, especially PCL, are of great interest among the plasticizers that may be used for PVC used in medical applications [25]. Studies dealing with the possibility of using PCL as a biodegradable, biocompatible and macromolecular plasticizer for PVC were reported in the 1960s [26]. Compared with PVC materials containing conventional plasticizers, the PVC/PCL blends are tougher and more extensible, with improved softness and higher resistance to extraction by oil and water [25, 27]. The glass transition temperature of compatible PCL/PVC blends was evaluated by Koleske and Lundberg from the dynamic mechanical tests (DMA) by means of a torsion pendulum [26]. The PVC/PCL blends containing less than 50 wt% PCL are transparent, flexible, plasticized products, despite the fact that PVC and PCL are two rigid polymers. The destruction of PCL crystallinity and plasticization of the PVC explain the softness of the resulting blend. DMA results showed that the PVC/ PCL blends display a single glass transition temperature, with values between the transitions of the blend components, over a wide range of composition. PCL is moderate polar, high-molecular-weight polyester, highly crystalline (50%), with a melting temperature around 60 °C. When blending over 40% PCL with PVC, crystallinity of PCL is reduced and two phases were observed: crystalline PCL and amorphous PVC/PCL blend, whereas only the amorphous PVC/PCL phase was noticed in blends containing up to 30% PCL [28]. PCL acts as a plasticizer for PVC in the amorphous phase, but “antiplasticization” occurred at very low concentration of PCL, explained by Sundben et al. as “pseudo-cross-linking” of the PVC [29]. PCL was investigated for its role as a processing aid and impact modifier in rigid PVC, as well as a permanent plasticizer in flexible PVC. The results showed that use of PCL at moderate level in rigid PVC significantly improved the melt processing, as well as modulus, tensile strength and kerosene resistance, with no effect over impact strength, but decrease of heat distortion temperature. When blended with flexible PVC, PCL induced crystallization over 35% and contributed to superior strength, ultimate elongation, resistance to kerosene and reduced volatility. Compared with conventional liquid polymeric plasticizers, PCL similarly reduced modulus and flex temperature in blends with PVC, but the melt processability was inferior to lower-molecular-weight plasticizers [30]. The possibility of partial/total replacement of the low molecular plasticizer di (2-ethylhexyl) phthalate (DEHP) from PVC medical devices with PCL was

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investigated by Rusu et al. [27]. Thermal and mechanical properties, the plasticizer loss and extraction behavior in different medical media, of different PVC compositions plasticized with PCL and PCL-DEHP mixture, were analyzed and compared with the data from the literature. The results suggest that PCL and the PCL-DEHP mixture are better plasticizers for PVC, with decreased extraction risk and similar or even improved thermal and mechanical properties. The decrease of Tg onset and Tg values in presence of PCL proves its role as macromolecular plasticizer for the PVC. A melting temperature was registered for PVC/PCL blends with 40 and 50% macromolecular plasticizer, indicating biphasic blends with distinct PCL crystalline regions. The PVC-PCL-DEHP ternary blends presented a single-phase structure, without a melting point. By increasing the amount of PCL plasticizer in PVC, a continuous decrease of Tg is observed also from DMA results, except for blend containing equal parts of PVC and PCL. Changes from brittle to tough plastics occur when PCL, DEHP or PCL-DEHP mixture is incorporated in PVC matrix.

10.4

PVC/Polysaccharide Bio-Related Blends

Polysaccharides are active biopolymers which offer real potential due to their physicochemical properties, short time biodegradability, non-toxicity, etc., and could be easily incorporated in the polymeric matrix by common techniques. Bigot et al. [7] developed a method for grafting of polysaccharides onto PVC surfaces. First, isothiocyanate groups (NCS) were introduced onto PVC surfaces using potassium isothiocyanate in a water/DMSO mixture. Then, unmodified seaweed antibacterial polysaccharides were directly grafted onto PVC–NCS surfaces using ionic liquid which played a concomitant role of solvent and catalyst.

10.4.1 PVC/Starch Blends The availability, low cost and high biodegradability of starch have made this polymer a desired material for producing bio-related materials for different applications, especially packaging. Studies dealing with various techniques of starch incorporation as filler in PVC formulations to produce potentially biodegradable plastics were started in the 1974. Co-precipitation of cross-linked starch xanthate with PVC latex, co-concentration of a starch and PVC latex, and dry mixing of starch and PVC were used to incorporate three levels of DOP and different amounts of starch in PVC matrix [31]. The first two methods and the use of pregelatinized starch led to obtaining of the most uniform and transparent plastics. Filler separation from the PVC resin was observed for plastics produced by dry mixing. The resulted tensile strengths were higher than those for the controls for blends with 50% DOP and up to 30% starch.

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The starch-filled plastics absorb water and could be biodegraded by a mixture of microorganisms commonly occurring in soil. The influence of starch incorporation into PVC plasticized with di(2-ethylhexyl) adipate (which is susceptible to fungal attack) was assessed by Rosa et al. [32]. Tensile strength at break and elongation at break reduced, while Young’s modulus increased with raising the starch contents of the mixture, indicating that the incorporation of starch decreased the plasticized PVC/starch blend flexibility; therefore, a more rigid material resulted due to the formation of new intermolecular interactions probably owing to hydrogen bonds. FTIR results showed that plasticizers interact with amorphous regions of PVC but do not interact with starch. The increase of the starch amount led to a higher absorbance in the stretching C–Cl for PVC. Regarding the spectra for the C–OH band related to starch, the variation of recorded vibration values indicates there is an interaction between hydroxyl groups of starch and C–Cl groups of PVC. The encapsulation of starch by PVC matrix could explain the slow, gradual loss of weight during aging in simulated soil for mixtures with larger starch content. The mechanical properties of PVC/starch blends are also influenced by the domain size and the interfacial adhesion between components. Nakamura et al. found out that both the dispersibility of starch and the yield stress of the blends obtained by the solution method were superior to those by the powder method [33]. Prior to melt blending, powders of PVC and starch were mixed in the powder method, whereas the starch aqueous solution was initially prepared, and then the PVC powders were added to the solution and finally dried in the solution method. Synthetic films are particularly effective to protect food products against mechanical damage. The extend of the shelf life of refrigerated Brussels sprouts coated with PVC combined with starch-based coatings formulated using glycerol (G-PVC), sorbitol (S-PVC) or glycerol plus sunflower oil (O-PVC) was evaluated at 0 °C for 42 days [34]. The optimum quality conditions were maintained for all sprouts treatments in the first 14 days. Browning of cut zones and losses in weight and firmness were minimized in PVC-packaged sprouts, especially in G-PVC, while ascorbic acid and total flavonoid contents remained almost constant and radical scavenging activity increased after 42 days of storage.

10.4.2 PVC/Chitosan (CS) Blends Chitosan is the deacetylated form of chitin, the second most abundant natural polymer after cellulose, extracted from the shells of crustaceans. Chitosan is a natural polysaccharide used in different fields due to its special properties, antimicrobial and antifungal activities, biocompatibility, biodegradability and non-toxicity. Modification of CS with PVC can lead to promising materials for a variety of applications. The possibility of blending CS with PVC through simultaneous

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casting of their separate solutions in suitable solvents was presented previously in this chapter [3]. Carrier-mediated blends of CS with PVC for different metal ions have been prepared by casting method in suitable solvents, in the presence or not of dithizone nanoparticles [35]. Inter-chain distribution of PVC and CS chains was proved by FTIR, while thermal analysis showed that blending with CS retards the decomposition of PVC due to the homogeneity or compatibility between CS and PVC. CS/PVC blends exhibit enhanced ability to uptake metal ions from their FeCl3 and CuSO4 aqueous solutions compared with PVC, increasing directly with the content of CS in the blend. Active PVC-based composites were prepared by thermo-mechanical process, with good mechanical–physical properties and antimicrobial activity [5]. PVC/ chitosan composites containing up to 40 wt% chitosan were manufactured by using an internal mixer at 150 °C for 10 min, at a mixing rate of 100 rpm. The specimens for characterizations were obtained by compression molding. The data showed that the elastic modulus increased 2 times over neat PVC, as the chitosan content increased in the blends, while no significant variation in tensile strength was observed. The authors explained these mechanical properties by the activation of a stress transfer mechanism across the PVC/chitosan interface. At a concentration of 40 wt% chitosan, the elastic modulus increased by 150 MPa and the elongation at break drops by 170%. These results confirm that CS promoted the stiffening of PVC. The antibacterial activity of the PVC/chitosan 40 wt% showed a considerable inhibitory activity against S. Aureus ATCC 6538 activity (97% reduction) and a partial activity against E. coli ATCC 25,922 (35% reduction). The authors explained this by the partial reduction of polycationic chitosan amount available to bind to negative charged bacterial surface, due to dipole–dipole interaction between C–N bonds of CS and C–Cl bonds of PVC (Table 10.1).

10.5

PVC/Natural Filler Bio-Related Blends

In view of increasing demand for environmental protection, different fillers from renewable materials can be incorporated as reinforcements in PVC matrix in order to produce composites with low cost, overall lightweight and good mechanical properties successfully used as construction materials or in the automotive and Table 10.1 Composition of the PVC/CS composites and Tg values as determined by DMA analysis

PVC/CS blend (wt%) PVC PVC/15CS PVC/25CS PVC/30CS PVC/40CS Adapted from [5]

Tg (°C) 49 54 54 52 54

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Fig. 10.3 Possible mechanism of adhesion between PVC and aminosilane-treated newsprint fibers. Adapted from [43]

furniture industries. The natural fillers include wood fiber and lignin [36–38], as well as natural plant fibers such as jute, bamboo, rice straw and sisal [11, 39]. Many composites of PVC and natural fibers are incompatible due to the polarity difference, but in order to enhance the interfacial adhesion between natural fibers and PVC matrix and therefore the properties of their composites, several coupling agents were found to be effective, such as different types of isocyanates, maleic anhydride, silanes, etc. [40, 41]. The hydrophilic surface of fibers became more hydrophobic by treatment with coupling agents. In this case, the surface tension of wood fibers is reduced and approaches that of the molten polymer, improving wetting and adhesion via mechanisms such as diffusion and mechanical interlocking between treated fibers and the polymeric matrix [42]. A possible mechanism of adhesion between PVC and the primary amine of aminosilane-treated newsprint fibers was proposed by Matuana et al. [43]. This mechanism shown in Fig. 10.3 is supported by the bands at 1653 cm−1 due to the formation of amine salt. Ogunniyi reported as well the possibility that the amino group could also form cross-links by quarternizing the pendent chlorine groups [44]. Table 10.2 contains information referring to the materials, processing methods and most important changes in the properties of PVC bio-related blends containing some types of unmodified or treated natural fillers from renewable materials. Table 10.2 Several types of PVC bio-related blends containing natural fillers from renewable materials Material type

Materials/obtaining method

Properties

References

PVC/rubber-wood fiber (RWF)/ epoxidized natural rubber (ENR)

RWF loading: 0–30% 50/50 PVC/ENR; PVC stabilizer (4%): tribasic lead sulfate (TS-100 M); Haake mixer, 150 °C, 10 min, 50 rpm; compression molded into sheets (1-, 3- and 6-mm thickness): pressure of 14.7 MPa at 160 °C for 3 min

• Flexural modulus, Young’s modulus and hardness increased with the RWF loading • Impact strength, elongation at break and tensile strength decreased with the increase in RWF loading due to poor interfacial adhesion between the

[45]

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Table 10.2 (continued) Material type

Materials/obtaining method

Properties

References

hydrophobic PVC/ENR blend and hydrophilic RWF filler • SEM: Larger holes in 30 php RWF composite are a clear indication of pullout of agglomerated RWF of irregular shape PVC/jute fibers

Composites PVC/50 wt% jute fiber and PVC/50 wt% E-glass fiber prepared by compression molding Jute fiber contains lignin (12– 14%), hemicellulose (21– 24%), cellulose (58–63%), fats and waxes (0.4–0.8%), inorganic matter (0.6–1.2%), nitrogenous matter (0.8– 1.5%) and traces of pigment

• Mechanical properties such as (TS), (TM) and (BS) and of both types of composites were evaluated and compared. For jute fiber/PVC composite values of tensile strength (TS) = 45 MPa, tensile modulus (TM) = 802 MPa, bending strength (BS) = 46 MPa, bending modulus (BM) = 850 MPa and impact strength (IS) = 24 kJ/m2; TS, TM, BS, BM and IS of E-glass fiber/PVC composites were found to increase by 44, 80, 47, 92 and 37.5%, respectively • Thermal stability of E-glass fiber/PVC system was higher

[39]

PVC/Moso bamboo fibers

Moso bamboo particles were modified with potassium permanganate aqueous solutions and then filled in PVC matrix; mixing ratio of 7:3 (w/w) for pretreated Moso bamboo particles/granulated PVC; the mixture was molded in a hot press molding machine preheated at 170 °C for 3 min. and pressed at 180 °C by a pressure of 10 MPa for 5 min

• Maximum tensile strength of Moso bamboo particle-reinforced PVC composite (BPPC) of 13.79 MPa with 0.5% potassium permanganate treatment; modulus of rupture and modulus of elasticity reached their highest values of 30.36 MPa and 3261.89 MPa,

[10]

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Table 10.2 (continued) Material type

Materials/obtaining method

Properties

References

respectively, at 0.2% concentration • Potassium permanganate treatment led to uniform dispersion of Moso bamboo particles in PVC matrix (enhanced compatibility) and increased elongation at break and flexural deformation of BPPC • Melting temperature of 190.8 °C with 0.5% potassium permanganate treatment; the melting enthalpy of crystallization was reduced to 69.82 J/g with 0.2% potassium permanganate treatment • Water resistance for treated BPPC • Low concentration of potassium permanganate can oxidize OH groups of Moso bamboo cellulose; too high concentration would degrade Moso bamboo cellulose PVC/pineapple fibers

Pineapple leaf fiber: cellulose (70–82%) and lignin (5– 12%); 25–75 wt% fiber (10 cm long) in composites; compression molding technique (sandwiching 4 layers of fiber between 5 sheets of PVC), heated at 190 °C for 5 min between two steel molds under a pressure of 5 metric ton

• The best mechanical properties recorded for 55% fiber content: tensile strength (TS) of 48.8 MPa, tensile modulus (TM) of 773 MPa, bending strength (BS) of 75.6 MPa, bending modulus (BM) of 4.2 GPa, impact strength (IS) of 21.4 kJ/m2 • After exposure to different intensities of ultraviolet (UV) radiation (25–200 UV dose),

[46]

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Table 10.2 (continued) Material type

Materials/obtaining method

Properties

References

enhancements of mechanical properties were recorded. At 100 UV dose: TS = 57.3 MPa, TM = 932 MPa, BS = 87.5 MPa, BM = 5.2 GPa and IS = 26.3 kJ/m2 • Water uptake behaviors of the non-irradiated and UV-irradiated composites were observed • Good fiber–matrix adhesion (SEM) PVC/epoxidized natural rubber (PVC/ ENR)/oil palm empty fruit bunch (OPEFB) fiber and poly(methyl acrylate)-grafted OPEFB

OPEFB consists of 65% of cellulose and 19% of lignin; mixing the fiber (0–30%) and the PVC/ENR blends by means of Haake Rheomix at 50 rpm, mixing temperature 150 °C for 20 min

• Increasing of Young’s modulus, flexural modulus and hardness with the addition of grafted and ungrafted fiber to the PVC/ENR blends • Addition of PMA-g-OPEFB fiber led to increase in elongation at break and UTS and decrease in the flexural and Young’s modulus, compared to ungrafted fiber (grafting PMA onto OPEFB imparts some flexibility to the blend) • Grafting of the OPEFB fiber improved the adhesion between the fiber and the matrix (SEM)

[47]

PVC/flax fibers

45–55% continuous flax fibers in a PVC matrix (SolVin or NanoVin grades) • Flax fabrics are calendered with several layers of rigid PVC films, and then the “sandwich” is heat-compressed at 180 °C • Flax fabrics are coated with PVC latex and then heat-compressed

• Lightweight, thermal insulation, sound proofing and very good thermoformability, gluable, weldable and UV-resistant when suitably coated • Potential applications: automotive interior trim and rear shelves, building door panels,

(https://www. ptonline.com/ articles/firstpvc-long-fibercompositesdebut)

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Table 10.2 (continued) Material type

Materials/obtaining method

Properties

• FibroVin consists of sheets from 0.6 to 1.4 mm thick, made of 60% rigid SolVin PVC and 40% long glass fibers (5–10 cm or 1.95– 3.9 in.); production by two technologies, co-developed with Fibroline of Lyon, France: First, dispersion of PVC dry blend into the cut-glass fibers using an electrostatic field (Fibroline); then gelation of the PVC dry blend without shearing (SolVin)

ceiling panels, partition walls, furniture and marine applications (decorative panels and partition walls). The Autoflax line also could compete with epoxy/ flax composites in sporting goods like rackets, as well as furniture and luggage

References

PVC/newsprint cellulosic fibers

• Dioctyl phthalate (DOP) as plasticizer (7.5 phr); ground waste inked newsprint as the filler • Fibers were treated with c-aminopropyltriethoxysilane (A-1100), dichlorodiethylsilane, phthalic anhydride and maleated polypropylene • Solvent-free system (dry blending) by spraying and mechanically mixing 0.1% of silanes on the surface of fibers • Compounding of PVC and PVC/(45 phr) newsprint fiber composites—in a high-intensity turbine mixer; rotating speed: 22.8 m/s; initial mixing: 100 °C, the compounded materials were discharged from the mixer at the pre-set temperature of 190 °C

• The empirical acid and base characteristics (electron donor/ acceptor abilities) of untreated and treated fibers, as well as plasticized PVC, were determined by inverse gas chromatography (IGC) technique • Aminosilane—a suitable adhesion promoter for PVC/ wood composites, improving significantly tensile strength of the composites; aminosilane-treated cellulosic fibers can react with PVC to form chemical bonds (FTIR)

[43]

PVC/leather fibers

10, 20, 30, 40, 50 and 60 wt% of short leather fibers (2 mm); formulations with a fiber content >40 wt% were difficult to process Continuous extrusion at 180 ° C through a flat die to produce leather‐like sheets with highly plasticized PVC (45.8 wt% plasticizer (dioctyl phthalate)

• Composites thermally stable below 200 °C;– fibers are dispersed in the composite up to a fiber content of 30 wt% (no fiber orientation, as flexible fibers bend and coil during flow); Flexible and resistant composites that exhibit

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Table 10.2 (continued) Material type

Materials/obtaining method

Properties

and 0.5 wt% of commercial stabilizers and antioxidants)

sufficient water absorption to be suitable for several applications in the footwear and clothing industry • Composites can be formulated and processed at high productivity levels and at a low cost

References

PVC/wood flour

Amine-containing natural polymers (chitin and chitosan) —novel coupling agents (0– 10 wt% based on the weight of wood flour in the composites); wood flour: 75 phr; high-intensity mixer, room temperature, 10 min; extruded through a 32-mm conical counter-rotating twin-screw extruder with an L/D ratio of 13:1 (Brabender) into 10-mm diameter rods, at 190 °C for all zones; 40 rpm extrusion speed

• Cost‐effective; increased flexural strength by * 20 %, flexural modulus by * 16 %, and storage modulus by 33–74 % compared to PVC/ wood‐flour composite without the coupling agent;-significant improvement in performance was attained for 0.5 wt% of chitosan and 6.67 wt% of chitin used in composites;increased interfacial adhesion between the modified wood surface and the PVC matrix occurs through acid – base interactions between the chlorine-containing PVC and amino groups on the surface of wood flour

[42]

PVC/lignin

Five types of lignin and lignin derivative used: a partially water-soluble lignin (PWSL), softwood sodium lignosulfonate (SF NaLS), hardwood sodium lignosulfonate (HD NaLS), hardwood organosolv lignin (Alcell), softwood kraft lignin (Indulin); melt compounding in a Haake Rheomix 600; temperature of 195 °C; time

• An interaction occurring between OH groups of lignin and a hydrogen of PVC (changes in strength at yield and break of the polyblends and IR spectra); This interaction decreases: Indulin > Alcell > PWSL > SF and HD NaLS;-weathering

[37]

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Table 10.2 (continued) Material type

PVC/banana (stem) particulate

Materials/obtaining method

Properties

of mixing 8 min; 65 rpm; 67% filling coefficient (net chamber volume 60 cm3). A Q–U–V accelerated weathering tester was used (rain and dew simulated). Materials exposed to UV-A 340 lamps receive an irradiance of 0.72 W m at 340 nm. The UV irradiance from 295 to 400 nm is 39 W m−2 nm−1 (±10%)

stability of the blends is lower than of neat PVC (lignin decrease the impact strength of the blends);-thermal stability higher for the hydrolytic and organosolv lignins and lower for the lignosulfonates and kraft lignins;-softwood lignins could give better results than hardwood lignin; Composites containing softwood lignins require a lower processing temperature, which reduced lignin decomposition processes;-accelerated weathering yields to a certain degree of crosslinking within most blends; PVC – Indulin blends: reflect both a certain degree of crosslinking (increase of Tg) and some degree of chain scission (tan d increasing)

Alkali-treated Nigerian banana stem particulate (reinforcement): 0, 8, 16, 24, 32 and 40% Kankara kaolin clay (filler): 20%; compression molding (220 °C, compression pressure of 20.7 MPa for 20 min)

• Overall lightweight and good mechanical properties; composition with 8, 72 and 20% of banana stem particulates (reinforcement), PVC (matrix) and Kankara clay (filler) has optimum mechanical property of 42 MPa and is estimated to have a long-term stress value of 25 MPa (corresponding to 40% loss in strength over 32 years), water absorption of 0.79%, Young’s modulus of 1.3

References

[8]

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Table 10.2 (continued) Material type

Materials/obtaining method

Properties

References

GPa and density of 1.24 g/cm3 • Incorporation of reinforcement/filler in the composite increased the thermal stability of the composite by 38.6% over that of pure PVC (TGA) and improved creep stability at elevated temperatures • Composite satisfied Williams–Landel–Ferry (WLF) assumption with reduced stiffness to 0.65 GPa over an estimated period in excess of 100 years of usage indicating better long-term performance than PVC pipe material • Composite offered price savings per meter length of 84 and 42% when compared with carbon steel and neat PVC pipe PVC/ENR/kenaf core powder (KCP)

PVC initially premixed with 50 phr stabilizer dioctyl phthalate (DOP) and 3 phr plasticizer (Cd/Ba stearate); 70 PVC/30 ENR ratio; untreated or treated kenaf core powder with benzoyl chloride (5, 10, 15 and 20 phr); melt processing on Haake Rheomix Polydrive R 600/ 610 at 140 °C and 50 rpm

• Presence of benzoyl chloride grafting on kenaf core powder (FTIR) • Elongation at break reduced with the increase of KCP loading (increase in stiffness of the compound) • The enhancement of mechanical properties suggested that the treatment improved the interfacial adhesion between kenaf core powders with PVC/ ENR matrix (SEM)

[49]

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PVC/Protein (Collagen) Bio-Related Blends

Lungu et al. [50] prepared by rolling-pressing and extrusion new polymeric blends based on PVC and natural polymers (hydrolyzed collagen and a hydrolyzed collagen/elastin mixture) for medical use. The physical and mechanical properties and also in vitro biocompatibility studies performed on a primary culture of human dermal fibroblasts by the MTT test proved the use of hybrid materials in the manufacture of medical devices on the conventional processing equipments. By mixing PVC with collagen, relatively homogeneous systems were obtained and the surface polarity increases by hydrolyzed collagen (HC) incorporation. Results showed the improvement of hydrophilicity and thermal stability of PVC. Also, the rapid dissolution of the collagen-based materials is avoided when the PVC/collagen blend is in contact with biological fluids; thus, a better biological stability in terms of resistance to enzymatic digestion was achieved [51]. PVC/HC blends are degradable in active sewage sludge [52] or by burial in the soil of terrestrial plants [53]. The degradation effect increased with the content in the natural polymer. In the first case, more susceptible for the degradation are the UV-irradiated blends (30 h). After the migration of the components with a small molecular mass in the environment, the natural polymer was degraded. In the second case, following the growth of Triticum (wheat), Helianthus annus minimus (little sunflower), Pisum sativum (pea) and Vicia X hybrida hort, during a vegetation cycle in the presence of the plasticized PVC/HC blends, the authors found no morphological and physiological modifications of the plants, the products released in the culture soil being not toxic for the plant growth.

10.7

PVC/ Poly(Vinyl Alcohol) (PVA) Bio-Related Blends

PVA is a useful biodegradable polymer which can be blended with a synthetic polymer such as PVC to facilitate its biodegradation in the environment. Prepared by the hydrolysis of polyvinyl acetate, PVA is a water-soluble semicrystalline synthetic polymer, with crystallinity index dependent on the synthesis process and physical aging. Among PVA’s applications, one can mention adhesives, wood and furniture, paper-coating, tannery, paints, textiles, agro-industries and biodegradable polymer products. In order to study their biodegradation in soil, de Campos et al. prepared films of PVA/PVC and PVA/PCL [54]. Both blends were prepared similar to homopolymer films by mixing the two components (PVA/PVC 1:1, w/w) at 65 °C and vacuum evaporating the solvent. PVA and PVC were solubilized separately in the first 15 min, the solutions being further mixed and shaken for 30 min to prevent the phase separation. The PVA/ PVC film with thickness of 90–110 µm resulted by evaporation of the mixture at 65 °C and 100 mmHg. The respirometric results

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showed higher biodegradation of PVA/PVC blend in the soil compared with the other polymers. Pre-mixing methods and saponification degrees of PVA influence the resulting properties of PVA/PVC blends. Nakamura et al. employed two different pre-mixing methods, powder method and aqueous solution method for obtaining PVA/PVC blends [55]. In the first method, the powders of both components were blended before melt kneading by a mixing roll. In the aqueous solution method, the PVC powder was added to as-prepared PVA aqueous solution, followed by drying and then clashing before melt kneading. When using PVA with saponification degree of 98 mol% and powder method, the authors found PVA domains of several hundred lm dispersed in the PVC matrix, while the aqueous solution preparation method changed the PVA domain sizes from sub-lm to several lm. Morphological results showed no influence of pre-mixing method on the domain size for PVA with saponification degree of 88 mo1% and below, the domain size being of about several ten lm for both methods. The finest dispersion of PVA from about 5 to 10 lm resulted when poly(methyl methacrylate) (PMMA) was added into the PVC/ PVA blend, in both powder and solution methods.

10.8

Conclusions and Future Trends

This chapter presented some possibilities of blending PVC with natural additives/ biodegradable polymers in order to obtain eco-friendly materials. It is well established that PVC materials present some drawbacks due to the use of non-renewable chemicals and non-biodegradable waste materials. The PVC biomaterials are of great interest in view of the reduction of petroleum-based resources and, in general, in a more intelligent utilization of natural resources. Combined with nanofillers/nanofibers/biodegradable polymers and their mixture, PVC bio-related blends are definitely more environmentally friendly than pure PVC, which is suspected to create potential hazards in the environment because of its high chlorine component. It is obvious that manufacturing and development of PVC bio-related blends make a good contribution to solve the environmental problems. The natural additive/biodegradable polymers used to obtain PVC biocomposites, their particle size, as well as their concentration and the interfacial adhesion between components are important factors affecting the properties of PVC bio-related blends. Generally, the mechanical properties and thermal stability were found to increase in comparison with pure PVC. The main markets impacted of PVC bio-related blends are in the field of building and construction, electric and electronics, auto, agriculture and medical. The large production of PVC biocomposite materials with low cost and performing properties to meet the needs of more people are among some key points that represent the main challenges with sustainable material development.

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