Polypropylene Melt-Blown Fiber Mats and Their Composites 9783031325762

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Engineering Materials

Yahya Kara

Polypropylene Melt-Blown Fiber Mats and Their Composites

Engineering Materials

This series provides topical information on innovative, structural and functional materials and composites with applications in optical, electrical, mechanical, civil, aeronautical, medical, bio- and nano-engineering. The individual volumes are complete, comprehensive monographs covering the structure, properties, manufacturing process and applications of these materials. This multidisciplinary series is devoted to professionals, students and all those interested in the latest developments in the Materials Science field, that look for a carefully selected collection of high quality review articles on their respective field of expertise. Indexed at Compendex (2021) and Scopus (2022)

Yahya Kara

Polypropylene Melt-Blown Fiber Mats and Their Composites

Yahya Kara Mechanical Engineering Program, Physical Sciences and Engineering Division King Abdullah University of Science and Technology (KAUST) Thuwal, Kingdom of Saudi Arabia Mechanics of Composites for Energy and Mobility Laboratory King Abdullah University of Science and Technology (KAUST) Thuwal, Kingdom of Saudi Arabia

ISSN 1612-1317 ISSN 1868-1212 (electronic) Engineering Materials ISBN 978-3-031-32576-2 ISBN 978-3-031-32577-9 (eBook) https://doi.org/10.1007/978-3-031-32577-9 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 This work is subject to copyright. All rights are solely and exclusively licensed 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

This book is based on the Ph.D. thesis of Yahya Kara, defended on the 5th of December 2022 at Budapest University of Technology and Economics, Budapest (Hungary). The thesis committee consisted of Prof. Dr. Péter János Szabó (chairman), Prof. Dr. György Marosi, Prof. Dr. Gábor Dogossy, Dr. Dániel Vadas, Dr. Tamás Turcsán, and Dr. Csilla Varga who have approved the content.

Preface

This book investigates the scope of manufacturing Polypropylene (PP) Melt-Blown (MB) fibers and their sustainable, recyclable self-reinforced composites applications. MB PP fiber’s thermal, morphological, and physical properties were systematically and comparatively investigated within the extent of this book. This book provides essential information on MB PP fiber properties and their applications in the polymer composite field. The book aims to provide a more in-depth look at melt-blowing and enlarges the knowledge of PP MB fibers’ structure–property–parameter relationship. The book further proposes a straightforward method of manufacturing multiscale, sustainable PP Single Polymer Composites (SPC). SPC’s thermal, mechanical, morphological, and structural characteristics were comparatively analyzed. The book also introduces a method of producing carbon-nanotube-doped PP MB fibers and their hierarchical PP composites. The book benefits researchers, professionals, and material scientists working on synthesizing PP fine fiber mats by melt processing. This book also believed to be useful for those working with PP fibers and related composites to manufacture sustainable, multiscale thermoplastic composite structures. Thuwal, Kingdom of Saudi Arabia

Yahya Kara

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Acknowledgments

I would first like to thank my colleagues, research fellows, and students for their great support and patience during my research journey. I want to express my gratitude to the Department of Polymer Engineering, Faculty of Mechanical Engineering, Budapest University of Technology and Economics and all its member staff for all their support and guidance. I would also like to thank Mr. Henk van Paridon (Borealis Polymers N.V.) and Mr. Katsuya Kawahara (Idemitsu Kosan Company, Ltd.) for supplying materials for my research. I started writing this book in Budapest (Hungary) and completed it in Thuwal, Jeddah (The Kingdom of Saudi Arabia); thanks to all providing help and support during this period. Last but not least, I would like to express my deepest gratitude to my beloved family, who always took pride in my achievements and supported me in all possible ways.

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Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Aims and Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 1 4 4 5 5

2 Literature Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 The Melt-Blowing Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.1 Materials Used for Melt Blowing and Their Properties ..... 2.1.2 Fine Fiber Mats and Their Applications ................. 2.1.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7 7 8 19 32 33

3 Understanding the Structure–Property-Parameter Relationship of Polypropylene Melt-Blown Fibers. . . . . . . . . . . . . . . . . 3.1 Materials and Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.2 Melt Blowing Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.3 Producing Reference Polypropylene Sheets via Compression Molding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.4 Characterization Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Results and Discussion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.1 Parameters Affecting Fiber Morphology. . . . . . . . . . . . . . . . . 3.2.2 Porosity and Pore Size. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.3 Tensile Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.4 Analysis of the Fiber Formation Mechanism and the Fiber Structure Development: DSC and WAXD Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

43 43 43 43 46 46 50 50 54 56

58 65 66

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Contents

4 Multiscale Single-Polypropylene Composites: Melt-Blown Polypropylene Fiber Mat Interleaving. . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Materials and Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.2 Producing Polypropylene Blend Film for the Matrix ...... 4.1.3 Melt Blowing Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.4 Film Stacking and Related Process Parameters ........... 4.1.5 Characterization Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Results and Discussion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Fiber Mat Morphology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 Characterization of the Mechanical Behavior ............. 4.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

67 67 67 68 68 70 72 75 75 78 84 85

5 Development of Multiwalled Carbon Nanotube Doped Polypropylene Melt-Blown Fiber Mat Interleaved Hierarchical Single-Polypropylene Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 5.1 Materials and Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 5.1.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 5.1.2 Producing MWCNT-Doped Polypropylene Blends. . . . . . . . 88 5.1.3 Producing Polypropylene Blend Film for the Matrix . . . . . . 88 5.1.4 Rheology Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 5.1.5 Melt Blowing Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 5.1.6 Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 5.2 Results and Discussion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 5.2.1 Analyzing Multiwalled Carbon Nanotube Doped Polypropylene Blends Rheology and Thermal Properties . . . 94 5.2.2 Analysis of Multiwalled Carbon Nanotube Doped Polypropylene Melt-Blown Fiber Mat Morphology, Thermal and Mechanical Properties. . . . . . . . . . . . . . . . . . . . . 96 5.2.3 Analysis of Multiwalled Carbon Nanotube Doped Polypropylene Melt-Blown Nanocomposite Fiber Mat Interleaved Single-Polypropylene Composites. . . . . . . . 100 5.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 6 Conclusion of Experimental Results and Future Suggestions ....... 6.1 Summary of the Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.1 Evaluating Melt-Blown Fiber Applications From the Past to Today in a Nutshell ......................... 6.1.2 New Horizons Towards Sustainable, Recyclable Melt-Blown Fiber Mats and Their Composites.. . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

107 107 109 110 114

Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Nomenclatures

Latin Letters D df d lp E f Hc H cc Hm L crys Mw P p Pa r S T Ta Tg Tm V

Diameter (m) Fiber Diameter (m) Distance Between Lattice Planes (Å) Elastic Modulus (MPa) Hermans’ Orientation Factor (-) Crystallization Enthalpy (J/g) Cold Crystallization Enthalpy (J/g) Melt Crystallization Enthalpy (J/g) Crystallite Length (nm) Weight Average Molecular Weight (g/mol) Porosity (%) Pressure (bar) Air Pressure (Pa) Radius (m) Solidity (%) Temperature (°C) Air Temperature (K) Glass Transition Temperature (K) Melting Temperature (K) Volume (m3 )

Greek Letters γ˙ Γ λ ρa

Shear Rate (1/s) 2 Polymer Mass Flux (kg/m h) Thermal Conductivity (W/mK) 2 Areal Density g/cm ( ) xiii

xiv

ρ air ρp σ σUTS χ Ω

Nomenclatures 3 Air Density g/cm ( ) 3 Polymer Density g/cm ( ) Stress (MPa) Ultimate Tensile Stress (MPa) Degree Of Crystallinity (%) Rotation Speed (1/min)

Abbreviations AM CBT coPA CV DCD DSC EMA EVA EVOH FDM FFF FFT FRC FRP HDPE hPP ILSS LDPE MB MCC MEX MFI MWCNT nFRC OLA PA PAN PBT PC PCTFE PE PET PLA

Additive Manufacturing Cyclic Butylene Terephthalate Copolyamid Coefficient of Variation Die to Collector Distance Differential scanning calorimetry Ethyl (Methyl Acrylate) Poly (Ethylene-Vinyl Acetate) Ethylene-Vinyl Alcohol Fused Deposition Modeling Fused Filament Fabrication Fast Fourier Transformation Fiber-Reinforced Composite Fiber-Reinforced Plastic High-Density Polyethylene Homo-Polypropylene Interlaminar Shear Strength Low-Density Polyethylene Melt-Blown (Fiber, Fiber Mat, Nonvowen, etc.) Mat Consolidation Coefficient Melt Extrusion Melt Flow Index Multiwalled Carbon Nanotube Nanofiber-Reinforced Composite Oligomeric (Lactic Acid) Polyamide Polyacrylonitrile Poly (Butylene Terephthalate) Polycarbonate Polytrifluorochloroethene Polyethylene Poly (Ethylene Terephthalate) Poly (Lactic Acid)

Nomenclatures

PMIA PMMA PMP PP PPS PUR PVOH PVP PWM RFACS SC SCPLA SPC SPnC SRC SWCNT TPPI TSPI TPU WAXD WLF

Poly (m-Phenylene Isophthalamide) Poly (Methyl Methacrylate) Polymethylpentene Polypropylene Poly (Phenylene Sulfide) Polyurethane Poly (Vinyl Alcohol) Polyvinylpyrrolidone Pulse-Width-Modulation Robotic Fiber Assembly and Control Systems Stereocomplex Stereocomplex Poly(Lactic Acid) Single Polymer Composite Single Polymer Nanocomposites Self-Reinforced Composite Single-Walled Carbon Nanotube Thermoplastic Polyimide Thermosetting Polyimide Thermoplastic Polyurethane Wide-angle X-ray diffraction Williams–Landel–Ferry equation

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Chapter 1

Introduction

1.1 Scope One of the most important developments in polymer engineering and science is, without question, the production of polymeric nano-/micron fibers. In recent years, various techniques such as template synthesis [1], self-assembly [2], phase separation [3], melt-blowing [4, 5], solution blowing [6] and electrospinning [7] were developed and employed for producing nano-/micron fibers. Due to its simple manufacturing, high throughput rate, cost-effectiveness, fair control of fiber morphology, and use of various polymeric materials, melt-blowing is one of the most practical technologies. In melt blowing, the polymer melt is extruded through a die containing numerous small capillaries and then stretched via a jet of hot air. The higher air velocity toward low-velocity polymer jets provides stretching and drag force that rapidly attenuates the polymer jets into fine fibers. Then, the fibers are collected on the surface of a collector, mostly in the form of a random web. The lack of controlled stretching gives melt blowing technology a distinct advantage and a high production rate compared to other techniques makes melt blowing attractive for generating nano-/microfibers [8]. Many industries, including but not limited to transportation, energy, agriculture, medical/healthcare, and construction, use melt-blown (MB) fibers and associated products [9, 10]. Polypropylene (PP) is also one of the most extensively researched thermoplastic polymers and its commercial production dates back to 1957 in the USA and 1958 in the EU [11]. PP products are broadly utilized in day-to-day life applications, including sheets, films, containers, twines, ropes, and fibers [12–16]. Melt-blowing is one of the most suitable methods for producing fine PP fibers in large volumes. Like other extrusion-based polymer manufacturing methods, various additives and fillers can be mixed with the raw polymer to improve fiber characteristics [5, 17]. In particular, nanoparticle additives and fillers have been extensively investigated for their broad application due to their unique properties. Graphene oxide, carbon nanotubes (CNTs), nanoclay, and other nanofillers have been incorporated

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 Y. Kara, Polypropylene Melt-Blown Fiber Mats and Their Composites, Engineering Materials, https://doi.org/10.1007/978-3-031-32577-9_1

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1 Introduction

into polymer matrixes to enhance fine fiber mats’ mechanical, thermal, and electrical properties and related composite structures [18–20]. The reinforcing effect of the nanomaterials is complex because they also change the crystallization kinetics, the polymer additive interfaces and the polymer nanostructure. For example, one might expect that the CNTs embedded within the fibers may boost the modulus and strength of these fibers. However, achieving uniform dispersion of the nanotubes in a polymer matrix is challenging, and poor dispersion can result in deteriorated properties. This hampers the applicability of CNTs and other nanoparticles in actual industrial applications [21]. Therefore, new strategies and methods must be developed and implemented for the potential dispersion and distribution of nanoparticles and additives in the polymer matrices. The demand for personal protective equipment (PPE) made of MB fibers has soared to unprecedented levels due to the COVID-19 pandemic. The COVID-19 pandemic has caused the demand for PPE constructed of MB fibers to soar to previously unheard-of heights. According to reports, more than 50 billion nonwoven face masks were made just in 2020 [22]. On the other hand, the worldwide automotive nonwoven market was valued at around 10 billion USD in 2018 and is expected to reach 14.2 billion USD by 2026 [23]. There is a growing demand for fine fiber mats and nonwovens, either foreseen or unforeseen, like the COVID-19 pandemic. The process and the end-products of melt blowing are still being developed, and more study is still required. Precise control of solidity, porosity, pore size, fiber orientation, fiber entanglement, forming thinner fibers (e.g., < 500 nm) and improving mechanical and thermal performance must be unveiled to advance scientific and industrial knowledge. Fiber-reinforced thermoplastic composites boast outstanding characteristics, making them increasingly valuable in many sectors as substitutes for traditional composite and metal counterparts. Up to date, a wide range of thermoplastic matrices, including polyamide (PA), acrylonitrile butadiene styrene (ABS), polyethylene (PE), polypropylene (PP), poly-ether-ether ketone (PEEK), polyetherimide (PEI) and polyphenylene sulfide (PPS), has been utilized in the industry to make composites together with glass, carbon and natural fibers. The processing of these composites is similar to that of the matrix itself and therefore includes, but is not limited to, compression molding, injection molding, extrusion, thermoforming, and additive manufacturing. The application of thermoplastic composites covers a broad field, including automotive parts, aerospace applications, sporting goods, general machine elements, and many more. The composite laminates made of reinforcing fibers usually exhibit excellent inplane material properties; however, the matrix material and fiber-matrix interface dominate out-of-plane properties (e.g., interlaminar shear strength). Ply-to-ply interfaces of composite laminates possess weak areas of the structure (prone to failure) due to the nature of the laminates. An interlaminar toughening approach, e.g., incorporating sub-phases into the reinforcement and matrix interface, can solve this issue [20]. The continuous nano-/submicron fibers have a large surface-to-volume and

1.1 Scope

3

aspect ratios (length/diameter). Better interfacial strength than conventional reinforcing fibers is anticipated due to the fine surface morphology and possibly homogeneous dispersion of nano-/submicron fibers throughout the matrix. This will result in improved interfacial properties [24]. The interleaving strategies seek to reduce composite laminate failure mechanisms like transverse crack and delamination and improve the laminated composites’ resistance to various loading conditions. Enhancing fiber-reinforced polymer composites’ mechanical and thermal performance next to their recyclability and sustainability is at the top of the composite society’s agenda. Thermoplastic matrices, which are easily recyclable by melt processing, can partially address the recyclability of FRPs [25]. However, fiber fragmentation that results in stress concentration locations initiating fractures after reprocessing leads to severe material failures. Besides, the recycling process often deteriorates the mechanical properties of composites. Single-polymer composites (SPCs), also known as self-reinforced composites (SRCs) or homopolymer composites, might be the ideal candidate to overcome these challenges. SPCs are thermoplastic composites for which reinforcing fiber and the polymer matrix are from the same polymer family. They can be entirely recycled via melt processing. However, their production requires complex techniques (e.g., film-stacking, hot compaction, coextrusion) and sensitive processing parameter control to prevent the reinforcing fibers from being completely melted. The fiber-matrix consolidation parameters, such as pressure, temperature, and molding time, greatly affect the interlaminar properties and the laminae’s thermal and mechanical properties. The SPC’s low load-bearing ability compared to other thermoplastic composite counterparts and thermal performance remain to be developed for widespread use in the industry. This book aims to improve the knowledge of manufacturing MB PP fibers and to introduce a new concept of producing sustainable, multiscale PP composites. The detailed research studies in this book also focus on developing MB PP fibers and PPbased composites, a commodity polymer with broad implementation in day-to-day life applications. A comprehensive literature review of the recent developments in melt-blowing, the processing parameters’ effects on the structure and performance of fiber mats and MB fiber’s applications focusing on producing high-performance and sustainable polymer composites was conducted. Melt-blowing conditions and their effect on fiber properties were systematically and comparatively investigated, and fiber structure development was detailed accordingly. Later, manufacturing carbon nanotube-doped MB PP fiber was detailed, and the effect of nanotube-doping on PP fibers was discussed. A new concept of manufacturing hierarchical SPC using MB PP fibers was introduced, and the results were discussed in detail. This book provides up-to-date tools for evaluating MB PP fiber mats from processing to end-use. It also aims to extend the knowledge of manufacturing high-strength, sustainable, recyclable and environmentally friendly thermoplastic composites via fine MB PP fibers.

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1 Introduction

1.2 Concept This book aimed to give another dimension by extending understanding and providing up-to-date knowledge of melt-blowing MB fibers and their composites. For this purpose, melt-blowing processing was briefly summarized and recent developments in the field were presented. Furthermore, the book aims to open a new door to implementing MB fibers in polymer composites and promoting MB fibers for making sustainable, advanced engineering structures. To date, industry and academia have put considerable effort into developing meltblowing and MB fiber mats for respective applications. Despite the advances in developing evenly-distributed, high-porosity MB ultrafine fiber mats, there are still many challenges for further optimization, end-product designing, characterization, and process modeling. Even though many researchers have dealt with melt-blowing and related process dynamics, there is a lack of knowledge that analyzes fiber formation mechanisms, crystalline structure, thermal and structural behavior of MB fiber mats, molecular structure development and thermal behavior accordingly. The MB fiber properties and fiber mat performance are very sensitive to processing parameters. Current attention is devoted to the sustainability and recyclability of composite structures besides advancing their thermal and mechanical properties. These concerns in the composite research led to the development of SPCs. Although such structures are not new, difficulties in processing, limited load-bearing ability, and thermal performance still hamper their widespread applicability. Incorporating nano/submicron fiber interleaves can be feasible since only a small amount of such fine fibers may be sufficient to achieve high performance. The MB fibers performance of synthetic nano/submicron fibers might be enhanced by nanoparticle inclusion. One might expect that the nanoparticles embedded within the fibers may boost the modulus and strength of these fibers. However, achieving uniform dispersion of the nano inclusion in a polymer matrix is challenging, and poor dispersion can deteriorate properties. In this regard, developing fine fiber and composite manufacturing methods is demanded future engineering applications.

1.3 Aims and Objectives The main objective of this research is to explore structure & morphology, thermal and mechanical properties and the feasibility of producing MB PP fiber mats and their hierarchical polymer composites. The research objectives of this book are listed as follows: . To understand the relationship between melt-blowing parameters and fiber formation mechanisms that affect fiber morphology, crystalline structure, and thermal and structural properties. . To develop MB fiber mat reinforced SPCs and investigate the effect of fine fibers on the composite’s thermal and mechanical properties.

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. To develop a method for producing high-performance SPCs with MB fiber mat interleaving veils without compromising recyclability, lightweight and straightforward processability. . To develop nanoparticle-doped MB fibers with enhanced thermal and mechanical properties and apply them as interleaving veils for producing high-strength SPCs.

1.4 Conclusion This chapter aims to give the reader an outlook on the book’s scope on melt-blowing, MB fibers, and polymer composites made of MB fibers. Even though there is a broad literature knowledge on melt blowing, the fiber formation mechanism still requires a more in-depth look into the processing conditions to analyze fiber structure development. Polymer composites made of MB fibers have recently debuted in the field. The MB ultrafine fibers with unique properties offer developing sustainable highperformance composites for various applications. Nanoparticles are proven their concept for enhancing polymeric materials’ performance. Nanoparticle application is yet straightforward and expensive for generating MB fibers. In this chapter, the current state of the arts, research directions and gaps were briefly addressed to achieve self-bonded, defect-free, fine fiber mats made by melt-blowing and to manufacture sustainable and advanced polymer composites made of MB fiber mats.

References 1. Liu, S., Shan, H., Xia, S., Yan, J., Yu, J., Ding, B.: Polymer template synthesis of flexible SiO2 nanofibers to upgrade composite electrolytes. ACS Appl. Mater. Interfaces 12(28), 31439– 31447 (2020). https://doi.org/10.1021/acsami.0c06922 2. Kimizuka, N.: Self-assembly of supramolecular nanofibers. In: Shimizu, T. (ed.) SelfAssembled Nanomaterials I: Nanofibers, pp. 1–26. Springer, Berlin Heidelberg, Berlin, Heidelberg (2008) 3. Zhao, J., Han, W., Chen, H., Tu, M., Zeng, R., Shi, Y., Cha, Z., Zhou, C.: Preparation, structure and crystallinity of chitosan nano-fibers by a solid–liquid phase separation technique. Carbohyd. Polym. 83(4), 1541–1546 (2011). https://doi.org/10.1016/j.carbpol.2010.10.009 4. Wente, V.A.: Superfine thermoplastic fibers. Ind. Eng. Chem. 48(8), 1342–1346 (1956). https:/ /doi.org/10.1021/ie50560a034 5. Kara, Y., Molnár, K.: A review of processing strategies to generate melt-blown nano/microfiber mats for high-efficiency filtration applications. J. Indust. Textiles 1–44 (2021). https://doi.org/ 10.1177/15280837211019488 6. Gao, Y., Zhang, J., Su, Y., Wang, H., Wang, X.-X., Huang, L.-P., Yu, M., Ramakrishna, S., Long, Y.-Z.: Recent progress and challenges in solution blow spinning. Mater. Horiz. 8(2), 426–446 (2021). https://doi.org/10.1039/D0MH01096K 7. He, H., Kara, Y., Molnár, K..: In Situ viscosity-controlled electrospinning with a low threshold voltage. Macromol. Mater. Eng. 304(11), 1900349 (2019). https://doi.org/10.1002/mame.201 900349

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1 Introduction

8. Zuo, F., Tan, D.H., Wang, Z., Jeung, S., Macosko, C.W., Bates, F.S.: Nanofibers from Melt Blown Fiber-in-Fiber Polymer Blends. ACS Macro Lett. 2(4), 301–305 (2013). https://doi.org/ 10.1021/mz400053n 9. Özcan, M., Kam, E., Kaya, C., Kaya, F.: Boron-containing nonwoven polymeric nanofiber mats as neutron shields in compact nuclear fusion reactors. Int. J. Energy Res. (2022). https:// doi.org/10.1002/er.7652 10. Latko-Durałek, P., Durałek, P., Boczkowska, A., Kozera, R., Wróblewska, M., Mazik, A.: Characterization of thermoplastic nonwovens of copolyamide hot melt adhesives filled with carbon nanotubes produced by melt-blowing method. Journal of Industrial Textiles 51(1_ suppl), 1235S-1251S (2020). https://doi.org/10.1177/1528083720910213 11. Sailors, H., Hogan, J.: History of polyolefins. Journal of Macromolecular Science—Chemistry 15(7), 1377–1402 (1981). https://doi.org/10.1080/00222338108056789 12. Pawlak, A., Vozniak, I., Krajenta, J., Beloshenko, V., Galeski, A.: Strain-induced consolidation of partially disentangled polypropylene. Express Polym Lett 15, 940–956 (2021). https://doi. org/10.3144/expresspolymlett.2021.76 13. Lee, J., Lee, J.U., Lee, K.J.: Production of 3D Printer Filament Using Exfoliated Graphene and Recycled PP Composite and Their Application to 3D Printing. Applied Chemistry for Engineering 32(2), 157–162 (2021). https://doi.org/10.14478/ace.2021.1009 14. Virág, Á.D., Kara, Y., Vas, L.M., Molnár, K.: Single Polymer Composites Made of Meltblown PP Mats and the Modelling of the Uniaxial Tensile Behaviour by the Fibre Bundle Cells Method. Fibers and Polymers (2021). https://doi.org/10.1007/s12221-022-5138-4 15. Luna, C.B.B., da Silva, W.A., Araújo, E.M., da Silva, L.J.M.D., de Melo, J.B.d.C.A., Wellen, R.M.R.: From Waste to Potential Reuse: Mixtures of Polypropylene/Recycled Copolymer Polypropylene from Industrial Containers: Seeking Sustainable Materials. Sustainability 14(11), 6509 (2022). https://doi.org/10.3390/su14116509 16. Längauer, M., Zitzenbacher, G., Heupl, S., Plank, B., Burgstaller, C., Hochenauer, C.: Influence of thermal deconsolidation on the anisotropic thermal conductivity of glass fiber reinforced, pre-consolidated polypropylene sheets used for thermoforming applications. Polym. Compos. 43(4), 2264–2275 (2022). https://doi.org/10.1002/pc.26538 17. Wang, N., Sun, H., Yang, X., Lin, W., He, W., Liu, H., Bhat, G., Yu, B.: Flexible temperature sensor based on RGO/CNTs@PBT melting blown nonwoven fabric. Sens. Actuators, A 339, 113519 (2022). https://doi.org/10.1016/j.sna.2022.113519 18. Cakir, M.V., Kinay, D.: MWCNT, nano-silica, and nano-clay additives effects on adhesion performance of dissimilar materials bonded joints. Polym. Compos. 42(11), 5880–5892 (2021). https://doi.org/10.1002/pc.26268 19. Liu, J., Yu, P.: Annealing induced high-impact toughness of injection molded isotactic polypropylene filled with liquid-phase exfoliated graphene. Polym. Compos. 43(4), 2450–2459 (2022). https://doi.org/10.1002/pc.26554 20. Kara, Y., Acar, V., Seydibeyoglu, M.O.: 4—Mechanical properties of nanoparticle-based polymer composites. In: Mavinkere Rangappa, S., Parameswaranpillai, J., Yashas Gowda, T.G., Siengchin, S., Seydibeyoglu, M.O. (eds.) Nanoparticle-Based Polymer Composites. pp. 95–108. Woodhead Publishing, (2022) 21. Acar, V., Erden, S., Sarıkanat, M., Seki, Y., Akbulut, H., Seydibeyo˘glu, M.: Graphene oxide modified carbon fiber prepregs: A mechanical comparison of the effects of oxidation methods. Express Polymer Letters 14(12) (2020). https://doi.org/10.3144/expresspolymlett.2020.90 22. Phelps,T.,Sam, B. C.: Masks on the Beach: The Impact of COVID-19 on Marine Plastic Pollution, pp. 12–14 (2020) 23. Global Automotive Nonwoven Fabrics Market By Product, By Application, By Geographic Scope And Forecast. In., vol. 14801 p. 102. Verified Market Research (VMR) (2019) 24. Kim, J.S., Reneker, D.H.: Mechanical properties of composites using ultrafine electrospun fibers. Polym. Compos. 20(1), 124–131 (1999). https://doi.org/10.1002/pc.10340 25. Mészáros, L., Kara, Y., Fekete, T., Molnár, K.: Development of self-reinforced low-density polyethylene using γ-irradiation cross-linked polyethylene fibres. Radiat. Phys. Chem. 170, 108655 (2020). https://doi.org/10.1016/j.radphyschem.2019.108655

Chapter 2

Literature Overview

Abstract This chapter aims to facilitate an outlook on melt-blown fiber mats and related composites by reviewing the recent developments in melt blowing, meltblown fiber mats and their related applications, nano-/submicron fiber reinforced composites. The chapter also focuses on advancing sustainable fibers and composites via knowledge. The literature overview summarizes the materials used in the melt blowing, the effects of processing parameters on the structure and performance of the fiber mats and their products, thermal and physical properties, mechanical behaviors of fiber mat interleaved and reinforced composites, and related composite manufacturing methods and their potential implementation in polymer and composite science & engineering.

2.1 The Melt-Blowing Process Melt-blowing is a nearly 70 years old- simple, versatile, cost-effective, extrusionbased fiber spinning technology that generates continuous nano/microfibers with the aid of high-speed hot air. The fiber mat is produced continuously, and the polymer melt is drawn and dragged by pressurized hot air. No special additives or binders are required, and there is no need for secondary processes like thermal bonding of the fibers. MB fiber mats have a high surface area per unit weight, moderate stiffness, and tunable permeability. MB fine fibers can also be utilized in a wide range of applications, including drug delivery, membrane separation, battery separators, skin and wound dressing, filters, surgical drapes and gowns, protective apparel and reinforced composite materials [1–5] and they played a crucial role in the fight against the COVID-19 pandemic [6] as the most common filtering media in personal protective equipment, such as face masks and respirators. MB fiber mats are formed directly from a molten polymer without controlled stretching. This renders a distinct cost advantage and high production rate compared to other micro-and nanofiber manufacturing techniques [7, 8]. Besides, melt blowing is a solvent-free process that makes it economical and environmentally friendly. The properties of the polymer materials must be optimized to meet the requirements of specific applications. These features may include but not limited to hydrophobicity/ © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 Y. Kara, Polypropylene Melt-Blown Fiber Mats and Their Composites, Engineering Materials, https://doi.org/10.1007/978-3-031-32577-9_2

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8

2 Literature Overview

hydrophilicity, piezoelectric or antistatic properties, biocompatibility or biodegradability, high filtration efficiency or absorbency of liquid matters, possessing a high modulus and strength, etc. Often a combination of multiple properties is desired, and that can be achieved with precisely engineered equipment operated within a relatively narrow processing window, accurately designed processing parameters, or a combination of two or more synthetic materials [9]. Wente [10] created the technique for the first time in the 1950s at the U.S. Naval Research Laboratory to capture radioactive particles in the upper atmosphere. Wente could generate polyamide and polyester fibers as thin as 100 nm by hot air steam. Wente’s concept was similar to manufacturing mineral wool patented by Player [11] in 1870. The patented process involved blowing a strong stream of air across a falling flow of liquid iron slag. When a powerful blast of steam met the liquid slag, that separated the melt into long filaments. Another patent by Hall [12] carried out the industrialization of a similar method in 1902 to produce highly porous mineral wool felt. The idea of applying hot air steam for fiber generation was followed by another patent authored by Thomas of the Owens-Corning Fiberglass Corporation [13] in 1940 to manufacture glass wools. Wente reported nanofibers of PET, PA6 and PA6/10 polymers with an average diameter of 500 nm and achieved production rates of 0.54–1.62 kg/h/m of die width. Later on, a 36-inch-wide (914 mm) die based on this concept was developed by Exxon Company [14]. Exxon improved the technology to commercially attractive throughput rates of 2.15–40 kg/h/m [15]. After the first steps of Wente in the’50 s, today’s well-known companies like DuPont [16], Exxon [17], Kimberly-Clark [18], Johnson and Johnson [19], 3 M [20] and many others [21–24] took an active part in developments and industrialization of melt blowing and MB fibers in the advancing years [25]. Nowadays, Reicofil Reifenhauser provides multi-row meltblowing lines with 12,000 nozzles per meter and fibers ranging from 1 to 25 microns and a throughput rate of up to 150 kg/h/m [26]. A Chinese producer, Zhejiang CL Non Woven Machinery Co Ltd. [27], offers an industrial-scale melt blowing unit with a daily capacity of up to 6 tonnes. Melt blowing is currently one of the fastest-growing, high-throughput, and most cutting-edge techniques for producing nano-/microfiber mats, among other techniques like electrospinning. A typical melt-blowing setup (Fig. 2.1) comprises four major components: an extruder, melt-blowing die head, hot air feed, and a collector consisting of a drum, continuous band, or fixed plate.

2.1.1

Materials Used for Melt Blowing and Their Properties

A broad range of polymers and polymer blends are compatible with melt-blowing. The most common polymers for melt blowing are polyolefins (especially PP) due to their physical properties, ease of processing, low cost and versatility in making a wide range of products. Table 2.1 lists the most common polymers used in melt blowing technology to manufacture micro/nanofibers.

2.1 The Melt-Blowing Process

9

Fig. 2.1 Schematic of a typical melt-blowing system [Reproduced with permission from Multidisciplinary Digital Publishing Institute] [28] and Illustration of the melt-blowing fiber formation at the die

In general, a low molecular weight (Mw ) corresponding to low viscosity and a high melt flow index (MFI) [g/10 min] is desired. The narrow molecular weight distribution, the low viscosity and the high MFI provide a more uniform web with thinner fibers in the melt-blowing process due to higher attenuation applied through the hot air steam. The open literature mostly states that the suitable range of MFI for polymers used in melt blowing is 15–3,000 g/10 min [10, 43–45] as a rule of thumb. The high polymer viscosity and, i.e., low MFI yield thicker fibers; hence, the forming ultra-fine fibers advantage is lost [44]. A measure of the breadth of the molecular weight distribution is given by the ratios of molecular weight average and number average molecular weight (Mw /Mn ), called the polydispersity index (PDI). Jones [46] studied polydispersity’s influence on PP MB webs’ mechanical characteristics. The mechanical properties of PP MB webs are slightly affected by the changes in PDI. The strength of the fiber mat decreases with the increasing degrees of PDI. A narrow molecular weight distribution reduces the polymer’s melt elasticity and melt strength so that the melt stream can be drawn into fine fibers without excessive draw force [45]. However, broad molecular weight distribution results in fiber breaks and flaws because of melt instabilities and increases melt elasticity and strength [29, 43]. The decrease in elongation causes an increase in

10

2 Literature Overview

Table 2.1 A summary of polymers and corresponding fiber diameter, melt flow index and melt temperature utilized in the melt-blowing Polymer type

Average fiber diameter (μm)

MFI (ASTM D1238)

Melt temperature (°C)

References

Polypropylene (PP)

0.3

1500

220

[29]

Poly (phenylene sulfide) (PPS)

4.1

–

−

[30]

Poly (ethylene terephthalate) (PET)

5

375

315 280

[31, 32]

Polystyrene (PS)

0.38

(1.1)*

−

[29]

Polyamide (PA) (6, 66, 11, 12)

0.8

−

Polyethylene (LDPE, HDPE)

< 12

155

255

[33]

Poly (butylene terephthalate) (PBT)

0.44

250

265

[29]

Polycarbonate (PC)

1.1

15.4

370

[34]

Polyurethane (PU)

4

−

230

[35]

Polytrifluorochloroethene (PCTFE)

2

~600

254

[36]

Polymethylpentene (PMP)

3

3000

255

[37]

Poly (lactic acid) (PLA)

0.4

77.5

244

[38]

Thermoplastic elastomers (TPE)

5

25

285

[39]

Polyvinylidene fluoride (PVDF)