Vegetable Oil-Based Composites: Processing, Properties and Applications (Composites Science and Technology) 9819999588, 9789819999583

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Composites Science and Technology

Showkat Ahmad Bhawani Anish Khan Mohmad Nasir Mohmad Ibrahim Mohammad Jawaid  Editors

Vegetable Oil-Based Composites Processing, Properties and Applications

Composites Science and Technology Series Editor Mohammad Jawaid, Laboratory of Biocomposite Technology, Universiti Putra Malaysia, INTROP, Serdang, Malaysia

This book series publishes cutting edge research monographs comprehensively covering topics in the field of composite science and technology. The books in this series are edited or authored by top researchers and professional across the globe. The series aims at publishing state-of-the-art research and development in areas including, but not limited to: • • • • • • • • • • • •

Conventional Composites from natural and synthetic fibers Advanced Composites from natural and synthetic fibers Chemistry and biology of Composites and Biocomposites Fatigue damage modelling of Composites and Biocomposites Failure Analysis of Composites and Biocomposites Structural Health Monitoring of Composites and Biocomposites Durability of Composites and Biocomposites Biodegradability of Composites and Biocomposites Thermal properties of Composites and Biocomposites Flammability of Composites and Biocomposites Tribology of Composites and Biocomposites Applications of Composites and Biocomposites

Review Process The proposal for each volume is reviewed by the main editor and/or the advisory board. The chapters in each volume are individually reviewed single blind by expert reviewers (at least two reviews per chapter) and the main editor. Ethics Statement for this series can be found in the Springer standard guidelines here - https://www.springer.com/us/authors-editors/journal-author/journal-aut hor-helpdesk/before-you-start/before-you-start/1330#c14214

Showkat Ahmad Bhawani · Anish Khan · Mohmad Nasir Mohmad Ibrahim · Mohammad Jawaid Editors

Vegetable Oil-Based Composites Processing, Properties and Applications

Editors Showkat Ahmad Bhawani Faculty of Resource Science and Technology Universiti Malaysia Sarawak Kota Samarahan, Malaysia Mohmad Nasir Mohmad Ibrahim School of Chemical Sciences Universiti Sains Malaysia George Town, Malaysia

Anish Khan Center of Excellence for Advanced Materials Research King Abdulaziz University Jeddah, Saudi Arabia Mohammad Jawaid Institute of Tropical Forestry and Forest Products Universiti Putra Malaysia Serdang, Malaysia

ISSN 2662-1819 ISSN 2662-1827 (electronic) Composites Science and Technology ISBN 978-981-99-9958-3 ISBN 978-981-99-9959-0 (eBook) https://doi.org/10.1007/978-981-99-9959-0 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 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 Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore Paper in this product is recyclable.

Preface

This book provides solid, quantitative descriptions and reliable guidelines, reflecting the maturation and demand of the field and the development of vegetable oil-based composites. This book focuses on the different vegetable oils used for the preparation of composites such as olive oil and canola oil. The coverage of the book highlighted the most exciting fillers used in the preparation of vegetable oil-based composites. This book will be of interest to researchers working in the fields of composite materials, material science, applied science, and bio-wastes. This book will be useful for scientists working on the preparation of composite materials from natural sources. This book will be very helpful for students in the development of green and sustainable composite materials, as well as graduates in material science, chemical engineering, and biocomposite materials. The first introductory chapter “Introduction to Vegetable Oils” covers the basic information about vegetable oils and their application, and the second chapter “Vegetable Oil Based Polymer Composites—Processing Properties and Applications” provides information about the processing and applications of vegetable oil composites. Chapters “Olive Oil Based Composites” and “Canola Oil as a Bio-additive: Properties, Processing and Applications” covers the use of olive oil and canola oil for the preparation of various composites. Chapters “Vegetable Oil Based Polyurethane Composites” and “Vegetable Oil Based Epoxy Composites” describe the polyurethane and epoxy-based vegetable oil composites and their applications. Chapters “Fiber Reinforced Vegetable Oil Based Vinyl Polymer Composites” and “Natural Fiber Reinforced Vegetable Oil Composites” covers the use of various fibres in the processing of vegetable oil composites. The last two chapters “Vegetable Oil Based Nanoclay Composites” and “Carbon Nanotube and Graphene-Reinforced Vegetable Oil-Based Nanocomposites” describe about vegetable oil composites based on nano clay, carbon nanotubes and graphene-reinforced materials. Finally, we assure the readers that the information provided in this book can serve as a very important tool for anyone working on vegetable oil composites. We are grateful to all the authors who contributed chapters to this book and who helped to

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Preface

turn our thoughts into reality. Lastly, we are grateful to the Springer team for their continuous support at every stage to make it possible to publish on time. Kota Samarahan, Malaysia Jeddah, Saudi Arabia George Town, Malaysia Serdang, Malaysia

Showkat Ahmad Bhawani Anish Khan Mohmad Nasir Mohmad Ibrahim Mohammad Jawaid

Contents

Introduction to Vegetable Oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Saba Farooq and Zainab Ngaini Vegetable Oil Based Polymer Composites—Processing Properties and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aboobucker Sithique M. Olive Oil Based Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carlo Santulli, Mirajul Alam Sarker, and Md Enamul Hoque Canola Oil as a Bio-additive: Properties, Processing and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Farzana Ahmad, Sohail Abbas, Amina Bibi, Mohammad Luqman, and Muhammad Jamil Vegetable Oil Based Polyurethane Composites . . . . . . . . . . . . . . . . . . . . . . . Saima Khan Afridi, Khalid Umar, Tabassum Parveen, M. Hazwan Hussin, and Mohd Jameel

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Vegetable Oil Based Epoxy Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 Akash Pratim Bora, Pragati Agrawal, and Sumit H. Dhawane Fiber Reinforced Vegetable Oil Based Vinyl Polymer Composites . . . . . . 133 Shelly Biswas Natural Fiber Reinforced Vegetable Oil Composites . . . . . . . . . . . . . . . . . . 145 Sandip Budhe, Praveen Kumar Ghodke, Akash Pratim Bora, and Sumit H. Dhawane

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Vegetable Oil Based Nanoclay Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 Abul Hasnat, Abdul Moheman, Showkat Ahmad Bhawani, and Khalid M. Alotaibi Carbon Nanotube and Graphene-Reinforced Vegetable Oil-Based Nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 Abul Hasnat, Abdul Moheman, Mohd Amil Usmani, Showkat Ahmad Bhawani, and Khalid Mohammed Alotaibi

Introduction to Vegetable Oils Saba Farooq and Zainab Ngaini

Abstract Vegetable oil (VO) is a naturally occurring hydrocarbon in innumerable compositions and abundantly found in natural plants, seeds and fruits. Vegetable oils have gained a mammoth consideration in this new era due to their limitless applications in different sectors including biofuels, food, soaps, cosmetics, textile, paint and coating, and plastic industries. Numerous researches have been accomplished to improve vegetable oil extraction and usage in significant applications as binders, polymerizations and lubricants. This chapter recapitulates the basic introduction, composition, classification of vegetable oils and their significant roles in daily life. The most acquainted applications of vegetable oils are also summarized in this chapter. Keywords Fat · Glyceride · Hydrocarbon · Cooking · Epoxide · Fuel industry

1 Introduction Earlier human civilization preferred animal fats such as butter formed from the milk of goats, cattle and sheep, instead of vegetable oil. Vegetable oil discovery and development was originated as an alternative source. Afterward, the oilseeds pressing and the extraction especially from olives became the primary source of cooking oil. Other resources such as radishes, sesame seeds, or flax seeds have also been used for oil production. In the medieval period Egyptians, Chinese, and Europeans produced infusions of aromatic or medicinal plants (e.g., cinnamon and clove) in vegetable oils as solvents for nutritional and therapeutic purposes [1]. They used vegetable oils for preserving food [2], bio-lubricant [3], coating materials [4], tissue engineering S. Farooq · Z. Ngaini (B) Faculty of Resource Science and Technology, University of Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, Malaysia e-mail: [email protected] S. Farooq Department of Basic & Applied Chemistry, Faculty of Science and Technology, University of Central Punjab, Lahore 54000, Pakistan © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 S. A. Bhawani et al. (eds.), Vegetable Oil-Based Composites, Composites Science and Technology, https://doi.org/10.1007/978-981-99-9959-0_1

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[5], biofuels [6], preparation of skincare products and cosmetics [7] for grooming, moisturizers and emollience [8]. Vegetable oil is usually considered the chief class of renewable resources due to its applications and availability. Recently, numerous techniques (i.e., genetic transformation, catalytic transformation) have been developed to enhance the oil productions from (i) higher vegetative tissue biomass as compared to fruits or seeds and (ii) carbohydrates modification into oil [9]. Vegetative tissues, stem, roots and leaves will produce a higher content of renewable oil (triacylglycerol) than oilseeds (20–50%) [10, 11]. Renewable resources still in demand to cope with global warming, carbon dioxide level, and environmental pollution [12]. Vegetable oil is an essential part of the food industry due to its culinary usage and biodegradability, easily available and low costs [13]. The oil can be achieved from different parts of the natural resources such as leaf, seeds, flowers, roots. Cottonseed, soybean, canola, palm, peanut, sunflower are examples of crops producing vegetable oil [14]. The use of vegetable oil in the food industry is higher than that of industrial usage (5–7%) [15]. Vegetable oil has also been used as biofuel oil in diesel engines [16]. Currently, vegetable oil production contributes an important role in our regular diet and food industrial products. These types of oily products could also be beneficial as solvents or ingredients in versatile fields such as nutraceuticals, cosmetics, lubricants, paints and biodiesel [17]. Consequently, the reinvestigation of vegetable oil’s latest developmental strategies (i.e., extraction, modification, purification, or formulation) has become of great interest due to the promising forthcoming applications.

2 Basic Components of Vegetable Oils Triglyceride is the core moiety [18] with 95–98% of the component in the vegetable oils [19]. The types, positions and proportions of fatty acids in the backbone of glycerol have significantly contributed to the properties of triglycerides. Vegetable oils are structurally categorized into two parts which are glycerol and fatty acid [20]. In Fig. 1, glycerol moiety is attached with the three long-chain carbon-based fatty acids to form triglycerides similar to vegetable oil molecules. The physical appearance of the oil has also depended on the nature of the fatty acids either saturated oils or unsaturated oils [21]. Saturated oil has a single-bonded fatty acid nucleus at room temperature and exists in a solid form such as vegetable fat. While unsaturated oil has a double-bonded fatty acid nucleus at room temperature and exists in a liquid form and beneficial for food frying [22]. Due to this reason, unsaturated oils are healthier than saturated oils. The content of fatty acids in triglycerides is fluctuated depending on the cultivations, climatic and agronomic [21, 23]. The polyunsaturated fatty acids linseed oil associated with fruit extracts are effective for dietary antioxidant and anti-inflammatory benefits [24]. Other components such as non-glycerolipids and glycerolipids present in less than 5% in the vegetable oils. Nevertheless, these components play important role

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Fig. 1 Chemical composition of vegetable oils

in the nutritional values and biological activities of nutraceutical and pharmaceutical industries [25]. Examples of non-glycerolipids are free fatty acids, tocopherols, sterols, phenolic compounds, vitamins, proteins, pigments, water, while glycerolipids are phospholipids, mono-glycerides and diglycerides [26]. The detailed chemical composition of vegetable oil is illustrated in Fig. 1 [27]. The composition of the vegetable oils is always varied significantly due to various factors such as growth factors, environmental conditions, including location, cultivar selection, and processing techniques [28]. The quality of vegetable oil has become a debate among researchers due to the heterogeneous nature of the oils. To date, the quality of vegetables can be easily controlled by advanced skills to maintain the taste and flavor of oil. The stability and quality of VO are affected by the fatty acid composition, oxidation, triglyceride structure and native antioxidants via external factors such as oxygen, light, water activity, surface area, metals and antioxidants [29]. For example repeatedly heating changes the physical appearance of oil e.g., color and increased viscosity by fluctuating the fatty acid composition of oil via multiple-chemical reactions (i.e., hydrolysis, polymerization, oxidation) [30]. Though contaminants (i.e., mycotoxins) of VO from the packaging materials, environmental effects and production machinery can spoil the oil taste [31]. Mycotoxins, pesticides, heavy metal contaminations analyzed by, GC, HPLC, atomic absorption spectrometry, inductively coupled plasma, and ICP-MS [32].

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3 Classification of Vegetable Oil Vegetable oils are alternative renewable oils that yielded environmental benefits and energy security [33]. VO are classified based on daily usage as edible vegetable oil and non-edible vegetable oil (Table 1) [34]. Non-edible vegetable oils (e.g., linseed oil, rice bran oil, mahua oil) are commonly used as feedstock in the biodiesel industry [35] and bio-lubricants due to their properties over refined oils which are biodegradable, cheaper and less toxic. The oils have high viscosity, lubricity, and flash point [36]. Non-edible oils have higher thermal efficiency than edible oils and highly preferred in the automotive industry [37]. The edible vegetable oils, on the other hand, are essential for regular cooking in the kitchens [38, 39]. This is because edible vegetable oil is an essential part of the human diet to provide energy, fatty acids, and fat-soluble vitamins. Common sources of edible oils are soybean, palm, peanut, soybean, cottonseed, olive, sunflower and rapeseed [40]. Edible oils comprise higher levels of fatty acids and natural micronutrients (i.e., tocopherols, phytosterols, carotenoids) than non-edible oils. Phytosterols and tocopherols are biologically active nutritional constituents that are usually found in vegetable oils with the ability to prevent cancers, diabetes and cardiovascular diseases. Moreover, tocopherols (both α- and γ-tocopherol) are the most effective lipid-soluble antioxidants [41] and commonly used in food products such as chocolate, meat products, margarine and spread, bakery stuff, and ice-creams [42]. Table 1 Edible and non-edible vegetable oil Properties

Edible oil

Non-edible oil

Source nature

An edible plant used as a source

The non-edible plant used as the sources

Examples

Palm oil, peanut oil, etc.

Linseed oil, rice bran oil, mahua oil

Usage

Directly used as human food for cooking purposes

Used in biofuel, soap, paint, detergent

Health and hygienic

Health, hygienic and have nutritional elements

Not necessary to be hygienic and healthy

Chemical processing

Chemical processing not required

Different chemical processing required

Cost

Slightly expensive due to extra-purification

Cheaper and economic for industrial scale

Introduction to Vegetable Oils

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4 Extraction of Vegetable Oil Extraction of VO is a vital process to improve the supply and stock of market prerequisite for bioactive compounds to contribute to the agriculture and food industry [43]. Initially, raw material is treated with enzymes (i.e., natuzyme, kemzyme, protizyme™, viscozyme L, termamyl and alcalase) before extraction process. The mechanical expression plays a prodigious role in cell wall loosening and facilitates higher yield of product (Fig. 2) [44]. After enzymatic treatment, further extraction process of raw material is performed to obtained desired products. The earlier extraction techniques employing Soxhlet and other conventional processes [45] are connected to numerous environmental and technological barriers that cause various issues such as solvent toxicity, high energy usage, and safety and control for the final product [46]. Alternative techniques (ultrasound, microwave, supercritical fluids, pressurized, Bligh and Dyer liquid extraction [47]) have been used in the extraction of VO. These greener techniques have significant revenues in terms of energy, cost, environment, time. Green solvents such as n-hexane and n-butane are preferred for the extraction of oils. Moreover, water gives the impression of less green due to its high CO2 emission and high energy consumption mandatory for evaporation. The other aqueous solutions were also avoided due to the threat thermally or biologically to the environment. It is auspicious to produce that type of water in the subcritical region, e.g., between critical point (374 °C) and boiling point (100 °C) and, has been evidenced efficiency in extracting polar and a polar compounds, that change polarity based on temperature than pressure [48]. Alternatively, several organic solvents are preferred for vegetable oil extraction’s purposes at an industrial scale to meet the current challenges such

Fig. 2 Numerous enzymatic extractions techniques and their products

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Fig. 3 Applications of vegetable oil

as competitiveness, economy and environment. Additionally, a suitable alternative solvent is recommended for the regulations of intra-industry, cosmetics and food in particular.

5 Applications of Vegetable Oil Vegetable oils have unique application in different industries as illustrated below in Fig. 3.

6 Fuel Industry The increasing energy consumption on daily basis for automobile vehicles and industrialization purposes due to the limited resources of petroleum oil. Moreover, petroleum oil are evaded due to the existence of sulfur content that cause pollutions [49]. The limited reservoir of petroleum obstacles can be controlled by renewable resources of biofuels [50]. Petroleum oils or crude oils obtained from the fossils, covered with sediments under pressure. Crude oil-derived diesel fuels are commercially used in vehicle engines due to more energy and efficiency. Whereas, biofuelsderived biodiesel gained from organic matter such as vegetable oils, sugarcane, and waste feedstock. Biodiesels are different from diesel fuels in terms of properties and composition. The general physicochemical properties of biodiesel and diesel fuel reported for comparative study in Table 2 [51]. The viscosity and volatility of biodiesel adjusted by the transesterification because VO has low volatility and

Introduction to Vegetable Oils Table 2 Properties of biodiesel and diesel fuel [51]

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Properties

Biodiesel

Diesel

Density at 15 °C (kg/m3 )

852–922

838–872

Viscosity at 40 °C (mm2 /s)

2.2–17.14

2.5–5.7

Flash point (°C)

70–241

50–98

Cloud point (°C)

−25 to 26

−17 to −8

Pour point (°C)

−28 to 18

−36 to −30

Cetane number

37.55–76.74

45–55

CFPP

−8.63 to 16

−38 to −6

Iodine number

60–128.7

0–38

Heating value (MJ/kg)

34.4–45.2

42–45.9

higher viscosity [52] cause hindrance for the direct usage in diesel engines [53]. After transesterification results were improved and satisfactory [54, 55]. Biofuels are biodegradable, renewable and non-toxic fuels that gained attention in the research sector [56]. Biofuels (e.g., bioethanol, charcoal, biomethane) exist in solid, liquid and gas forms (Fig. 4) [57, 58]. The liquid form of biofuels i.e., bioalcohol (i.e., bioethanol, biobutanol or biogasoline), green diesel (produced via hydrocracking), bioether (oxygenated fuels), straight VO (edible oils), biodiesel (transesterified VO) [59]) used for electricity production through turbine running and transportation fuel in engines of vehicles.

Fig. 4 General types of biofuels

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S. Farooq and Z. Ngaini O OH

Transesterif ictaion

OH

3 CH 3OH

OH

O O O O

O O

R' R' R'

Technology f or triglyceride conversion

HO

+

HO

O

Diglycerides Monoglycerides Acids Waxes

R' R' R'

HO

Catalytic deoxygenation

Hydrotreating

O

n-C15 n-C16

Decarboxylation Decarbonylation

isomerization

n-C15 n-C16

caracking alkane n-C17 n-C17 n-C18 isomerization n-C18 propane

Hydrogenation / Dehydration O O

R

O

Cracking

OH O

CH2

H2

H2C

OH O

CH 2 H 3C

OH

CH 3 H2

H3 C

+ CO2

Fig. 5 General techniques for the modification of vegetable oils (a); The life cycle of biodiesel (b)

The triglycerides of vegetable oils are modified by various processes such as hydrotreating [60], cracking [61], deoxygenation [62] and transesterification (Fig. 5a). Cracking is a conventional process for the decomposition of vegetable oils to achieve more organic products (i.e., alkanes, alkenes) [63]. Cracking and transesterification are not compatible with diesel engines due to high oxygen content [64, 65]. This can be overcome by catalytic hydro-processing of the vegetable oils known as deoxygenation. The resultant hydrocarbons (oxygen-free) are compatible with conventional diesel engines [65]. Catalytic deoxygenation is a process to synthesize bio-hydrogenated diesel (BHD), also known as green diesel [66]. The life cycle of biodiesel is illustrated in Fig. 5b [67]. Deoxygenation of fatty acids in VO are following three pathways namely decarbonylation (DeCO; removal of oxygen in form of CO), decarboxylation (DeCO2 ; elimination of oxygen in form of CO2 ) and hydrodeoxygenation (HDO; removal of oxygen in the form of H2 O) [68]. The consumption of H2 for fatty acid’s deoxygenation is in the following order: DeCO2 < DeCO < HDO. Numerous catalysts (such as Zn–CaO, Fe–CaO, Ni–CaO, and Co–CaO) able to speed up the deoxygenation process and increase H/C ratio [69]. This process is efficient and economical for the commercial usage of biofuels at an industrial and non-industrial scale.

7 Plastic Industry Vegetable oils are unique and versatile feedstock for bio-polymeric materials such as polynaphthol, polyester amides, polyamides, polyesters [70] and also for plasticizers [71] in the plastic and rubber industry [72]. Numerous techniques have been introduced to design monomer, dimer, polymer and polymer composites from natural resources with useful properties (e.g., high strength, modulus, flame retarding, resistance characteristics) that comparable to petro-chemically designed conventional

Introduction to Vegetable Oils

(a)

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(b)

(c)

Fig. 6 Vegetable oil derived polymer (soybean oil and lignin polymer) (a); physical appearance of the achieved polymer (b and c)

polymers [73]. The unsaturated fatty acids monomers with one or more than one carbon–carbon double bond (–C=C–) make vegetable oils appropriate to design biopolymer via polymerization processes. Linoleic and oleic acids are two types of fatty acids in VO that are commonly used for bio-based polymers [74]. The vegetable oils are chemically modified to achieve the required viable properties (e.g., chemical reactivity), mechanical properties (such as modulus, strength, or toughness), and thermal properties (e.g., glass transition temperature) [28]. Polyurethane foams, for example, are useful for sound and thermal insulation, furniture, mattresses, construction, packaging, cushioning, transportation of goods [75, 76]. Fibers and fillers-based vegetable oil-polymer matrices depicted a better-quality property to extend applications. Biopolymer of polyurethanes having 85% of bio-content which can be prepared from the incorporation of soybean oil and lignin via non-isocyanate reaction (Fig. 6a). Biopolymer of polyurethanes is feasible for various applications such as elastomers, thermoplastic film, sealants [77]. In 2020, Liang and coworkers synthesized polyurethane polymer from the interaction of castor oil with octahydro-2,5-pentalenediol (OPD). These polymers consist of the flexible region (i.e., fatty acid chain of castor oil) and rigid nucleus of OPD which advantageous for the waterborne polyurethane (WPU) films for the preparation of elastomeric polymers to rigid plastics. These PU films showed an upsurge trend in glass transition temperature. Furthermore, the bicyclic diol reduced the free volume to increase the rigidity (Fig. 7) and refined the stiffness of films by controlling the movements of the molecular chain [78].

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Fig. 7 Diagram of PU film’s network of castor oil (a); Network of the PU films of OPD and castor oil (b); Monomeric structure of WPU network (c)

8 Textile Industry Vegetable oils contribute an important role as a softening and anti-wrinkling agent [79]. Traditionally, tallow (animal fat) was used for the improvement of fabric properties but it caused some drawbacks i.e., skin diseases, irritation, itching, dermatitis, extra stiffness of clothes and permeability to air and water. The replacement of tallows with vegetable oils (such as pine oil, castor oil, vegetable oil, coconut oil, rice barn oil, sunflower oil, palm oil) able to produce soft and comfortable clothes [80]. Moreover, water-repellent is also compulsory for textile industries for cotton or fiber finishing. VO derived from transesterification used as a water repellent in cotton fibers. The water repellents (such as alkyl urethane, dimethylpolysiloxane (1), polyethylene waxes (2), Fixapret CL (3), fluorocarbon repellent (polyacrylic and polymethacrylic acid ester) (4) Fig. 8 [81]) are used to avoid the spreading of water [82]. In polydimethylsiloxane repellent, silicon interacted with fibers via hydrogen bonds that increase seam slippage and pilling, which decrease the water repellency [83]. This problem is reduced by introducing fluorinated coatings for textiles which imparts fireproofing and waterproofing without damaging the fabric permeability to vapor and air. Fluorinated coatings as water repellent attributes to chemical resistance, low surface energy, low friction and thermal resistance [84]. Vegetable oils derived from polyurethane foams is useful for the removal of the dyes from the effluents of the textile industry to avoid river contaminations. It has good absorptivity for the textile dyes [85].

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Fig. 8 Vegetable oil derived water repellent

9 Soap Industry For decades, tallow, shea nut oil, groundnut oil was used as the main source in the soap production. These oils significantly affect the properties of soap such as lathering, texture, color and cleansing power properties. Tallow oil increases the lathering of soap while groundnut oils increase the cleansing power [86]. Saponification involves basic hydrolysis of vegetable oils or fat [87] to form soap. Strong alkaline in saponification is not suitable for home soap due to its reactivity in humid air with carbon dioxide [88]. Waste cooking oil has higher fatty acid that solidified easily. Whereas, surface-active agents are required in adequate amounts because their excess amount for soap formation has reduced the stability of the soap [89]. Waste cooking oils have the same composition as cow tallow. The waste exists in a liquid form and is commonly collected in restaurants, homes and caterings. Improper disposal of oils can disturb aquatic life and blockage the sewage system. Nevertheless, the waste cooking oil can also be utilized for soap production [90]. Green soap from waste materials such as almond shells (as exfoliating agent), orange peel (as colorant) and cooking oil are common feedstock to manufacture soap without any artificial additives. Figure 9 illustrated (a) waste cooking oil-derived soap, (b) olive oil-derived soap and (c) olive oil-derived soap with a natural colorant. The physical appearance of soap (b and c) is uniform, consistent and attractive than waste cooking oil [91].

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Fig. 9 Saponification, waste cooking oil (a), olive oil (b, c) derived soaps

Recently, antibacterial or antiseptic soap has become a popular choice with the addition of active antimicrobial components. These antimicrobial agents act as additives that can kill non-pathogenic microbes, even though not effectively deactivate the viral infections. Conventional antiseptic soaps are quite pricey. Many alternative and cheaper sources in soap production have been reported. New ingredients for the soap preparations have been reported from two types of vegetable oils—peanut and castor oil and blended with wood tar via cold process method. Wood tar is used as antiseptic components and suitable for the production of antibacterial soap. The yield of peanut oil soap is higher than castor oil soap. Peanut oil-derived soap formulations are more favorable to the commercial grades because of excellent cleaning power, pH = 9.29, high foamability and antibacterial sensitivity [92].

10 Food Industry as Preservatives Conventionally, fossil raw materials are preferred for plastic packaging and food protection [93]. In the twenty-first century, plastic materials produced from synthetic polymers (polyvinyl chloride (PVC)-plastics) have been extensively used with several improved properties such as water resistance, durability and low-cost properties in food packaging [94]. Despite many benefits, non-biodegradability is a serious environmental obstacle in recycling process and disposal. The progress and development of biodegradable materials have been achieved via facilitating non-plastic, biodegradable bags biopolymers i.e., polysaccharides and proteins [95]. Moreover, antimicrobial packaging able to slow down, or inhibits the growth of microorganisms [96]. The usage of antimicrobial agents (i.e., chitosan, clove, grapefruit seeds) contributed to extending shelf-life while maintaining the quality of packed material [97]. The biodegradable film of antimicrobial packages consists of antimicrobial agents in their formulation to stop the vapor between atmosphere and food, and also give intrinsic properties such as antimicrobial activities, biodegradable and biocompatible [98]. The different vegetable oils (such as coconut oil, rapeseed

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Fig. 10 Papaya transformation into edible film

oil, and hazelnut oil) addition in the biodegradable films gives explicit chemical, mechanical and physical properties [99] (i.e., opacity, thickness, appearance) [100]. Besides antimicrobial and biodegradable packaging, edible packaging was also designed from food additives (colorant, emulsifier, flavor, antimicrobial agent, plasticizer) edible biopolymer (polysaccharides, proteins, lipids), useful for fruits and vegetable packing [101]. Edible films are non-toxic, good stability, good appearance, adherent to food surface, prevent mold growth, economically viable, avoid water depletion from food, and tasteless or have a pleasant taste [102, 103]. For example, olive leaf extract and carrageenan-derived biofilm are used for beef packaging [104]. Edible films made from papaya associated with ascorbic acid and Moringa leaf extract, give significant antioxidant properties useful to food preservatives (Fig. 10) [105]. Moreover, the lipase enzymes played a vital role in food flavor maintenance [106].

11 Coating, Adhesive, Paint Industry Vegetable oils have also been utilized in coating, varnish, paints, biopolymers, binders and adhesives in paints and coatings materials [107]. The coating material is useful for film former, pigments and additives for long time [15]. The coating material composition is based upon the resins, pigment, solvent, additive (thickener, thixotropic agent, emulsifier, anti-sagging agent, siccative). Economic factors such as availability, chemical, and physical stability, supply, and price of oil are also important for the commercial production and demand of paints. Specific properties of oils are also analyzed for paint formulation such as color, acidity, viscosity, drying rate or time, arrangement and degree of unsaturated fatty acids, amount of saturated and

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unsaturated fatty acids, skinning time, stability underwater and heat, storage stability, wetting, flow and solubility characteristics [108]. Traditionally, coatings and vegetable oil have been commonly used as drying oil (i.e., linseed oil, walnut oil, tung oil, poppyseed oil and perilla oil). Drying oils are highly unsaturated oils, that are hard and thick due to air oxidation. This issue is overcome by the progress of renewable resources-based coating preparations with improved performance. Non-drying oils (i.e., almond oil, baobab oil, babassu oil, coconut oil, cocoa butter, Nahar seed oil [109], macadamia oil, mineral oil, olive oil, peanut oil) are not causing hardness in coating material when exposed to air, and give flexible, shiny and waterproof coating. Vegetable oil-derived coatings are being beneficial for particular purposes as corrosion protective, antimicrobial, architectural, electrically insulating, biodegradable, biocompatible, self-healing, decorative coatings [110], coil coatings, optical fiber coatings, and paper coatings. Vegetable oils can be transformed into alkyd, polyesteramide, polyetheramide, polyurethane, epoxy and polyol to make polymeric coating materials. For example, Linseed oil-derived coating materials prepared from linseed epoxidized oil reaction with diethanolamine to form waterborne oil, which formed resin by reacting with phthalic anhydride. The achieved resin was further mixed with phenol–formaldehyde to achieve the final coating, shown in Fig. 11 [111].

Fig. 11 Preparation of linseed oil derived waterborne-coating material

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12 Perspective and Conclusion Vegetable oils are low cost, biodegradability, commercially available and outstanding environmental aspects and enriched bioactive compounds. Scientists and researchers may develop novel technologies for the synthesis of polymers, binder, energy provider moieties with low solvent and mild temperatures, solvent-free, at room temperature requirements contributed to maintaining high yields and atom efficiency. Further modifications of vegetable oil-derived materials are still needed to introduce innovative properties; with improved performance, affordable cost and ecofriendly. With extensive and persistent research efforts, VO material will be beneficial in many industries and in the future. Acknowledgements The authors would like to thank the Ministry of Higher Education Malaysia for financial support through FRGS/1/2019/STG01/UNIMAS /01/1.

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Vegetable Oil Based Polymer Composites—Processing Properties and Applications Aboobucker Sithique M.

Abstract This chapter provides an overview of the processing, properties and applications of various vegetable oil based polymers suitable for composites manufacturing. Among the different sources of biomass feed stock, vegetable oils play a key role in the development of bio based polymers and sustainability issues. Functionalization of vegetable oil triglycerides via epoxidation, acrylation, maleinization, hydroxylation and subsequent conversion of polymers offers a variety of polymeric materials. Blending of epoxidized vegetable oil with petro based epoxy resins DGEBA and subsequent polymerization in the presence of bismaleimides offers a variety of bio based polymers suitable for high performance applications. Three different types of bismaleimides were used to prepare hybrid polymeric materials of high thermal stability and mechanical strength. SEM micrograms of the hybrid materials show interesting heterogeneous morphological characteristics. Flame retardation properties of the different bismaleimide modified vegetable oil based epoxy matrices were discussed.

1 Introduction Polymers and polymeric composite materials have helped man kind in many ways such as aerospace, automotive, marine, infrastructure, military, sports and industrial fields. These lightweight materials exhibit excellent mechanical properties, high corrosion resistance, dimensional stability and low assembly costs. However, polymers derived from petroleum reserves are limited and as the demand for polymeric materials increases there is a growing urgency worldwide to develop bio based products and other innovative technologies than can limit the widespread dependence of fossil fuel. In addition, global warming, caused in part by carbon dioxide released by the process of fossil fuel combustion has become an increasingly important problem A. S. M. (B) Associate Professor, P.G and Research Department of Chemistry, Islamiah College (Autonomous), Vaniyambadi 635 752, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 S. A. Bhawani et al. (eds.), Vegetable Oil-Based Composites, Composites Science and Technology, https://doi.org/10.1007/978-981-99-9959-0_2

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A. S. M.

and the disposal of items made of petroleum-based plastics, such as fast-food utensils, packaging materials and trash bags also creates an environmental problem. Petroleum-based or synthetic solvents are also contributing to air pollution. It is necessary to find new ways to secure sustainable development. Renewable bio-materials that can be used for both bio-energy and bio-products are a possible alternative to petroleum-based products. Recent advances in development of polymers from bio-based materials, natural fiber development, genetic engineering and composite science offer significant opportunities for improved materials from renewable resources with enhanced support for global sustainability. Bio polymers are considered as potential substitute for certain existing petroleum based polymers owing to their renewability and biodegradability. A wide variety of polymers can be derived from natural resources such as plants, animals and bacteria. Typical examples include vegetable oils, Cellulose, hemicellulose, lignin, starch, poly lactic acids, Chitin-Chitosan, silk, poly hydroxyl butyrate, etc.

2 Vegetable Oils A wide range of affordable and high performance materials can be made from using natural oils derived from both plant and animal sources. Huge amount of vegetable oils are available in most parts of the world, making them an ideal alternative to petroleum based raw material. According to statista research survey vegetable oil production worldwide in 2020–21 amounted to 209.14 million metric tons [1]. Vegetable oils are extracted from plant sources and they are quite abundant in nature, Soybean, linseed, canola oil, corn oil, cotton seed oil, castor, sunflower, rape seed, and palm oils are some examples of plant oils available worldwide. Vegetable oils have been used extensively in the food industry and for industrial applications. Soybean oil (SBO) is the most readily available and one of the lowest-cost vegetable oils in the world. The world’s production of soybean oil was almost 200,000 tonnes every year. Soybean oil is globally produced by USA, China, Argentina, Brazil and India. USA was categorized as the largest producer of soybean oil producing one billion pounds of soybean oil [2, 3]. Palm oil is produced in large quantity next to soybean oil. Malaysia, Indonesia, Sub-Saharan Africa, Thailand and Colombia are the biggest produce of palm oil [4]. Linseed oil has been used mainly used in paint Industry. Oils contains triglyceride molecule composed of three fatty acids joined at the glycerol unit as shown in the figure.

Triglyceride molecule a major component of Vegetable oil

Vegetable Oil Based Polymer Composites—Processing Properties …

23

The fatty acids vary from 14 to 22 carbon in chain lengh and possess 0–3 double bonds per fatty acids. Genetically Engineered plants such as soybean, corn oils possess increased number of double bonds for functionalization. Triglyceride oils have been used to produce coatings, plasticizers, lubricants, etc. Soy bean oil possesses the following composition of fatty acids. Fatty acid

Carbon chain length: double bond

Soybean oil

Myristic

14:0

0.1

Palmitic

16:0

11

Palmitoleic

16:1

0.1

Stearic

18:0

4.0

Oleic

18:1

23.4

Linoleic

18:2

53.2

Linolenic

18:3

7.8

Arachidic

20:0

0.3

Behenic

22:0

0.1

Average double bond/triglyceride

–

4.6

3 Functionalisation of Vegetable Oils and Production of Vegetable Oil Polymers Functionalization of the double bonds, the allylic carbon and ester groups via epoxidation, maleinization, acrylation helps in the production of vegetable oil polymers and improves the mechanical and thermal properties of the vegetable oil based polymers suitable for industrial applications. Functionalization helps to reach a higher level of Mw and cross-linking density, as well as to incorporate the chemical functionalities known to impart stiffness in a polymer network. From the natural triglyceride, it is possible to introduce acrylates, maleates and vinyl functionalities and also to convert the unsaturation into epoxy functionalities. It is also possible to obtain hydroxyl functionaltriglycerides (soy polyols) by the hydroxylation of epoxidized soy bean oil and is used in the production of polyurethanes.

3.1 Epoxidation of Soybean Oils Epoxidized natural trglyceride can be found in oils such as vernonia plant oil, or can be syntheised from unsaturated oils such as soybean oil or linseed oil by epoxidation reaction. The functionality of natural vernonia oil is 2.8 epoxy rings per triglyceride,

24

A. S. M.

whereas functionality of commercially available soybean oil is 4.1–4.6 epoxy rings per triglyceride. Epoxidation of soy bean oil is carried out in a 500 ml three-necked round bottom flask equipped with a thermometer sensor, a mechanical stirrer, and a septum pierced with an injection needle to equalize the pressure. The apparatus was kept in water bath to maintain temperature 80 °C. 100 gm of soy bean oil, 50 ml of toluene, 25 gm of amberlite and either 15 gm of glacial acetic acid or 11.8 gm of formic acid was added in to the RB flask. With agitation 83.7 g of 30% H2 O2 were added slowly through a separating funnel over a period of 30 min. The precaution was taken to prevent over heating of the system due to exothermic nature of epoxidation reaction (see Scheme 1). The epoxidation reaction takes place by electrophilic attack of peroxy acids on the double bond as given below (see Scheme 2). The kinetics of epoxidation of soybean oil studied in the presence of in situ formed peroxoformic and peroxo acetic acid at 40, 60 and 80 °C temperatures in the presence of ion exchange resin as catalyst. The activation energy was found to be 54.7 kJ/mol for the epoxidisation with peroxoacetic acid and 35.9 kJ/mol for the epoxidation of O

C

O

C

O

C

O

O

O

80oC

CH 3COOH / H 202

O O C

O

C

O

C

O

O

O

O

O

O

O

O

Scheme 1 Epoxidation of soy bean oil

H 2O 2

H 3CCOOH C C

H 2O

H

H

C

O

O O

CH 3COOOH

C

O

O R

Scheme 2 Mechanism of epoxidation reaction

C

C O

R

Vegetable Oil Based Polymer Composites—Processing Properties …

25

peroxoformic acid. At lower temperatures namely 40 and 60 °C peroxoformic acid was more efficient than peroxoacetic acid, whereas at 80 °C both peroxoacetic acid and peroxoformic acid is equally efficient. However, the extend of side reactions was found to be minimal with peroxoacetic acid between 40 and 80 °C range and somewhat higher in the case of peroxoformic acid at 80 °C [5]. Epoxidization of Soybean oil and Castor oil was carried out using hydrogen peroxide and Amberlite IR-120 and finally cured in the presence of cationic latent catalyst N-benzylpyrazinium hexafluoroantimonate (BPH). The activity of BPH was evaluated at different temperatures and the polymerized Epoxidized Castor oil showed relatively higher Tg and low coefficient of thermal expansion [6]. Park et al. [6] synthesized and characterized epoxidized soybean oil (ESO) and epoxidized castor oil (ECO). The cationic polymerization of ESO and ECO with a thermal catalyst N-benzyl hexafluoroantimonate (BPH) was initiated at 80 °C and 50 °C respectively. The cured ECO samples show a higher Tg and lower coefficient of thermal expansion than those of ESO, due to the higher intermolecular interaction in the ECO/BPH system [7].

3.2 Acrylated Epoxidized Soy Bean Oil Acrylation of soybean oil was carried out by reaction between epoxidized soybean oil and acrylic acid to form Acrylated Epoxidized soybean oil (AESO (Scheme 3)). AESO is used for surface coating and it is commercially available in the form Ebecryl860. Urethane and amine derivatives of AESO have been used in coating and ink applications. AESO is blended with styrene to develop polymers with high glass transition temperature. The properties of the polymer can be controlled by changing the molecular weight of monomer or the functionality of acrylated triglyceride. Addition of styrene imparts rigidity and strength to the triglyceride based polymer [9]. Khot et al. [8] studied the development and application of triglyceride based polymers and composites. Triglyceride oils derived from plant oils have been used to synthesize several different monomers for use in structural applications. These monomers have been found to form polymers with a wide range of physical properties. They exhibit a tensile moduli in the 1–2 GPa range and glass transition temperature in the range 70–120 °C. At low glass fiber content (35 wt.%), the composites produced from acrylated epoxidized soybean oil displayed a tensile modulus of 5.2 GPa, a flexural modului 9 GPa, a tensile strength of 129 MPa, and a flexural strength of 206 MPa [9].

26

A. S. M.

Scheme 3 Synthetic route for acrylate epoxidized soybean oil

3.3 Malenized Soybean Oil Monoglyceride (SOMG) Maleinization of soybean oil monoglyceride is done in two steps. First step is to convert the triglycerides of soybean oil into monoglycerides by standard glyceroloysis reaction. The second step is to react the monoglycerides with maleic anhydride. After maleinization styrene is added to increase polymerization conversion as well as to impart rigidity [9] (see Scheme 4). Maleinated hydroxylated (HO/MA) is synthesised in two steps. First step is the hydroxylation of oil in the presence of formic acid and hydrogen peroxide. Second step by reacting hydroxylated oil with maleic anhydridein the presence of dimethyl benzylamine catalyst. The detailed synthesis of HO/MA can be obtained from Khot et al. [8].

3.4 Vegetable Oil Polyols and Polyurethanes The conversion of double bonds of triglycerides to hydroxyl group leads to new areas of applications in urethane chemistry. Zlatanic et al. [9] synthesized six polyurethanes polyols derived from sunflower, canola, soybean oil, midoleic sunflower, corn and linseed oils. The polyols were synthesised in two steps, epoxidizaton of oil and subsequesntly ring opening of the epoxy groups to hydroxyl groups. The epoxidisation

Vegetable Oil Based Polymer Composites—Processing Properties …

27

Scheme 4 Maleinated hyroxylated soybean oil (HO/MA) polymer

was carried out in toluene medium in presence of per acetic acid. The oxirance rings were converted to polyols by ring opening with boiling methanol and in the presence of tetrafluoroboric acid catalyst. The polyols further reacted with isocyanates to yield polyurethanes. The linseed oil based polyurethane exhibited higher cross linking density and higher mechanical properties. The midoleic sunflower exhibited softer polyurethanes with lower strength and low glass transition temperature. The differences in the properties of different polyurethanes derived from different polyols was due to number of reactive sites i.e. double bonds in the fatty acids [10]. Another synthetic route for the synthesis of Polyurethanes from vegetable oil was studied in detail by Guo et al. [10]. The double bonds of soybean oil was first converted to aldehydes through hydroformylation reaction in the presence of Rh or Co as catalyst. The aldehydes are further hydrogenated by Raney Nickel to alcholols resulting in soybean oil polyol. The latter is reacted to Methylene diisocyanate to yield polyurethanes. The Rhodium catalyzed reaction leads to higher conversion (95%) rate of polyol and results in rigid polyurethanes whereas cobalt catalyzed reaction leads to poor polyol conversion rate (67%) and results in hard rubber with poor mechanical strength [11, 12]. Latere Dwan’Isa et al. [12] synthesized bio based polyurethane from soybean oil derived polyol and polymeric diphenylmethane diisocyanate. The cross-linked bio based polyurethane being prepared from soy phosphate ester polyols with hydroxyl

28

A. S. M.

content ranging from 122 to 145 mg KOH/g and pMDI at 150 °C show cross linking densities ranging from 1.8 × 103 to 3.0 × 103 M/m3 , whereas the glass transition temperature vary from approximately 69 to 82 °C. The cross-linking densities improved significantly for hydroxyl content of 139 and 145 mg KOH/g at curing time of 24 h. Similarly, the glass transition temperature and storage moduli are increased [13]. Vegetable oil polyols are industrial importance and should possess low viscosity and high hydroxyl content. Attempts were taken to synthesize varieties of halogenated and non halogenated soybean oil polyol using hydrochloric acid, hydrobromic acid, methanol and hydrogen. Brominated polyol had higher functionality of 4.1 hydroxyl value and other polyols possessed lower functionality. The bromine polyol posses higher density than chlorinated, methylated and hydrogenate. The methoxylated polyol was liquid and other polyols were sold waxes at room temperature [13]. Bharadwaj et al. (2002) synthesized polyurethane elastomers from castor oil based polyol, polyethylene glycol of various molecular weight and toluene diisocyanate. The sorption, mechanical and thermal properties have been studied. The diffusion coefficient and sorption coefficient were found to decrease with an increase in chain length of polyethylene glycol. The thermal degradation of all elastomers starts at 250 °C regardless of PEG chain length [14]. Zlatanic et al. [9] synthesized polyurethane networks from six different polyols derived from sunflower, canola, soybean, corn and linseed oils with 4,4' diphenylmethane diisocyanate. The differences in the network structure reflected the number of functional groups in vegetable oils and resulting polyols. It was observed that the canola, corn, soybean, and sunflower oils gave polyurethane resins of similar cross-linking density and linseed oil based polyurethane had higher cross-linking density and higher mechanical properties [15]. Vegetable oil-based polyurethanes with shape memory properties have been synthesized. The glycerol cross-linking point in the triglyceride structure are responsible for their permanent shape, while pendant groups including fatty acid chains and saturated fatty acid chains might contribute to their shape recovery effect because they are not involved in polymer backbone. A series of different structural soybean oil polyols were reacted with 1,6 diisocyanatohexane to fabricate polyurethane networks. This unique shape-memory property will afford the vegetable oil based polyurethane polymers a wide range of applications in medical and pharmaceutical fields [17]. The new bio-based epoxy resins were synthesised by fusion process between epoxidized soy bean oil and Bisphenol A, further crosslinked with curing agents like polyisocyanates of different structure: toluene-2,4-diisocyanate (TDI), hexamethylene diisocyanate (HDI) and 4,4' -methylene diphenyl diisocyanate (MDI). The obtained epoxy-polyurethane materials are characterized by various mechanical properties, which depend on the type of chosen isocyanate. Compositions. The HDI cured resin exhibit better mechanical characteristics than elastic polyurethane materials based on hydroxylated soybean oil. Materials cured with aromatic isocyanates MDI and TDI are characterized by higher mechanical resistance comparable with

Vegetable Oil Based Polymer Composites—Processing Properties …

29

cast polyurethane based on petrochemical resources. Epoxy fusion product cured with toluene-2,4-diisocyanate in a presence of Dabco T9 appears to have the best mechanical properties among all tested compositions [16]. The vegetable oil–lactate based polyols with high functionalities were used synthesize polyurethane materials. Epoxidized monoglycerided reacts with lactic acid to obtain soy polyol via epoxy ring opening reaction, the soy polyols were then reacted with isocyantes to yield polyurethane material. The incorporation of lactic acid into the polymers not only increased the glass transition temperature but also ensured that the polyurethane has an excellent biocompatibility. This broadens its application in bio medical field. The biocompatibility test of the polyurethane with mouse fibroblast cells L-929 showed that the cell could adhere and grow very well on the polyurethanes [17]. Polymer Laminates were produced with epoxy resins from waste vegetable oil (WVO) cured with methylhexahydrophthalic anhydride (MHHPA) and were reinforced with glass and flax fibres. Glass fibre-reinforced composites presented Young’s moduli similar to petro based (DGEBA) polymers but reduced tensile strength. WVObased resins greatly improved impact properties and reduced density without altering the thermal stability [18]. Athawale and Pillay [18] developed semi and full Interpenetrating networks (IPN) of uralkyd (UA) resin based on hydrogenated castor oil and poly(butyl acrylate). The IPN’S were characterized for their mechanical properties. The mechanical properties significantly increased by increasing UA component in the blend. Full IPN’S exhibited higher apparent densities, mechanical properties and thermal stability than the corresponding semi—IPN [19].

4 Vegetable Oil Based Epoxy Blends Though the vegetable oil based polymers reduces the demand for petroleum based polymers and contribute to sustainable development, it possess serious limitations. The triglyceride-based materials possess inadequate rigidity and strength due to the aliphatic nature of the resin [20]. This makes the pure vegetable oil based polymers are inadequate to prepare high performance materials. Several attempts have been made to improve the thermal and mechanical properties of vegetable oil based polymers by reinforcing natural fibers and metal oxide [21]. The epoxy resins first developed commercially are the glycidyl ethers based on diphenylolpropane (DPP), also known as bisphenol-A and epichlorohydrin (see Scheme 5). EVO blended with petroleum based resin Diglycidyl ether of bisphenol-A (DGEBA) to improve the properties of vegetable oil based polymers. Petro-bio epoxy blends possess several advantages such as improving the mechanical strength, reducing the demand for petro based resin contributing to lesser environmental degradation and sustainability.

30

A. S. M. CH3

O CH2 CH

CH2 Cl

+

HO

C

OH

CH3

-NaCl

CH2 O

C

CH3

OH

CH3

O CH2 CH

NaOH

O

CH2 CH

CH2 O

CH3

C CH3

O O

CH2 CH

CH2

n

Scheme 5 Formation of diglycidyl ether of bisphenol-A

The physico chemical and mechanical properties of Epoxidized castor oil (ECO) DGEBA blends cured with BPH latent thermal catalyst was studied. When 40 wt.% of DGEBA was replaced by ECO the glass transition temperature and cross linking density of the blends decreased with increasing ECO, however the flexural strength of the epoxy blends improved tremendously [22]. The mechanical and morphological properties of ESO-DGEBA blends cured with Triethylene tetramine (TETA) was studied by Ratna et al. The modified ESO (prepolymerised with TETA) and unmodified ESO were blended with DGEBA resin. Increasing the ESO concentraton in the case of unmodified ESO did not improve the impact strength, whereas the modified ESO significantly improved the impact strength with the optimum value of ESO [23]. Miyagawa et al. (2005a) processed bio based neat epoxy materials containing ELO and ESO using anhydride curing agent. A percentage of diglycidyl ether of bisphenol F(DGEBF) was replaced by ELO and ESO. Izod impact strength and fracture toughness were significantly improved dependent on epoxy content of oil. The phase separated morphology was studied using SEM [23]. The fracture toughness and impact strength of DGEBF/EVO blends cured with anhydride curing agent methyltetrahydropthalic anhydride (MTHPA) and 1methylimidazole as accelerator. EVO loading up to 50 wt.% in the DGEBF resin results in decreased Glass transition temperature and storage modulus [24] (see Scheme 6).

5 Bismaleimide Modified ESO-DGEBA Resin Several researchers studied the EVO—petro based epoxy resin blends in the presence of different curing agents. Loading of the EVO in the petro based resins results in improvement of certain mechanical properties such as tensile strength, impact strength, storage moduli. However, the thermal stability and glass transition temperature of the matrix decreases. The increased percentage of EVO greater than 40% leads to loss of both thermal and mechanical properties and results in the incomplete curing

Vegetable Oil Based Polymer Composites—Processing Properties … CH3 H2C

O

C H

CH3

OH

C

CH2 O

O

CH2 C H

31

O O

C

CH2 O

CH3

H2 C

C H

CH2

CH3

n

Diglycidyl ether of bisphenol-A (DGEBA) H O

O H2C

C H

C H

OH

CH2

DGEBA - Abbreviated form + O O C

O

C

O

C

O

O

O

O

O

O

O

O

Epoxidised soybean oil

60oC

H O

O H2C

C H

O C O

O

O

O

O O

O O

C O

C H

C

O

O

Soy based epoxy prepolymer

Scheme 6 Formation of soy based epoxy pre polymer

OH

CH2

32

A. S. M.

of the epoxy system. Hence, we have attempted to synthesize hybrid bismaleimide modified ESO-DGEBA amine cured bio based polymer matrix to overcome the limitations. Bismaleimides (BMIs) are used as matrix resins for high performance fibrereinforced composite materials in the aviation and space industries. These resins have better thermal stability, flame resistance and retention of mechanical properties at high temperatures than the epoxy resin. BMIs are synthesized from maleic anhydride and an aromatic or cycloaliphatic diamine. These monomers can be polymerized through polyaddition reaction with themselves as well as with other co-monomers without generating any volatiles. ESO is blended with DGEBA at various concentrations from 10 to 40 wt.%, beyond 40 wt.% loading of ESO the curing reaction with Diamino diphenylmethane (DDM) becomes incomplete. The optimum loading of ESO is found to be 30 wt.% of ESO (see Scheme 7).

5.1 Mechanical and Morphological Charactrization of BMI Modified Vegetable Oil Polymers The mechanical properties such as tensile strength, tensile modulus, flexural strength, flexural modulus and Izod impact strength is listed in Table 1. The incorporation of soy epoxy up to 30 wt.% in the DGEBA system enhanced the values of tensile strength and tensile modulus. Above this concentration the tensile strength values falls down. For example the tensile strength value of DGEBA system increased to 11.6%, 17%, 23% and 10.3% by the incorporation of 10, 20, 30 and 40 wt.% of the soy based resin respectively. Hence 30 wt.% soy oil epoxy is fixed for better mechanical characteristics of the materials. The inter cross linked network developed between aliphatic triglyceride polymer and aromatic bismaleimide chains leads to the improvement in the tensile strength of the matrices. Further, the decrease in the flexural strength and modulus is because of the rubbery nature imparted by the aliphatic chains of triglyceride oil. The 30 wt.% soy based epoxy matrices were further chemically reacted with three types of bismaleimides, namely N, N' -bismaleimido-4,4' -diphenyl methane (BMI-1), 1,3-bis(maleimido)benzene(BMI-2) and 3,3' -bis(maleimido phenyl)phenyl phosphineoxide (BMI-3) at various wt.% and finally cured with DDM curing agent. Incorporation of bismaleimides enhanced the values of tensile strength marginally. The incorporation of 5, 10, 15 and 20 wt.% of BMI-1 in the 30 wt.% soy based system improves the tensile strength by 0.4%, 4.3%, 9.2% and 17.9% respectively. Similarly, BMI-2 modified 30 wt.% soy based system, the tensile value increased by 6%, 10.9%, 11.3% and 15.4% and for BMI-3 modified system by 3.9%, 5.9%, 6.9% and 11.6% respectively. The increase in cross-linking density due to the homopolymerization of BMI is the cause for the improvement in the properties [25]. Among the different bismaleimide modified systems, BMI-2 exhibits higher tensile strength

Vegetable Oil Based Polymer Composites—Processing Properties …

33 H O

O H2C

C H

C H

O O

O

C

O

C

O

O

O

C

O

O

O

O

CH2

OH

O

Soy based epoxy prepolymer O

O H H2 N

C

NH2

N

R

N

H

4,4'-diaminodiphenylmethane

O

O

BMI

125 oC

H N

O N

H C H

O

R O

H

NH HO H2C C H

N O

OH HC

H2 C

O

N

O

O

N O

R N

HO

HO

O

O C

O

NH OH H

C

H

HO

R

N

N

HN

R

O

O

O

O

O

O

O N

OH HO HN

H C H

N

O

C

O

O

C

R O

O

O

O

H N

Scheme 7 Formation of bismaleimide modified hybrid soy based epoxy

N O

O

34

A. S. M.

Table 1 Mechanical properties different bismaleimides hybrid soy based epox matrices Composition

Tensile strength (MPa)

Tensile modulus (MPa)

Flexural strength (MPa)

Flexural modulus (MPa)

Impact strength (J/m)

D

62.8 ± 5

6671.3 ± 35

108.0 ± 7

1804.1 ± 40

98.2 ± 6

SE10

70.1 ± 5

7224.9 ± 33

104.5 ± 3

1749.8 ± 31

170.7 ± 5

SE20

73.5 ± 4

7413.6 ± 34

102.7 ± 3

1599.8 ± 26

175.8 ± 4

SE30

77.8 ± 3

7560.2 ± 29

97.4 ± 6

1433.2 ± 31

180.7 ± 8

SE40

69.3 ± 4

7422.6 ± 34

83.7 ± 6

906.6 ± 27

145.7 ± 6

SE30 B1–5

79.9 ± 3

7590.7 ± 30

115.6 ± 6

1522.0 ± 28

176.2 ± 5

SE30 B1–10

80.2 ± 5

7886.4 ± 36

117.7 ± 6

1584.6 ± 29

149 ± 3

SE30 B1–15

83.2 ± 4

8262.5 ± 31

123.0 ± 6

1644.2 ± 29

129 ± 4

SE30 B1–20

86.9 ± 5

8916.3 ± 29

125.1 ± 5

1686.6 ± 31

110 ± 4

SE30 B2–5

82.5 ± 5

7622.9 ± 31

119.2 ± 2

1582.6 ± 35

165.7 ± 5

SE30 B2–10

86.3 ± 4

82157 ± 30

120.4 ± 4

1629.3 ± 39

149.7 ± 6

SE30 B2–15

86.6 ± 3

8758. 5 ± 31

126.3 ± 4

1697.5 ± 39

118.7 ± 6

SE30 B2–20

89.8 ± 6

8986.5 ± 34

127.9 ± 3

1819.9 ± 36

86.5 ± 5

SE30 B3–5

80.9 ± 3

7610.6 ± 34

111.1 ± 4

1438.7 ± 32

168.1 ± 4

SE30 B3–10

82.4 ± 5

7916.3 ± 32

113.3 ± 3

1482.1 ± 32

132.9 ± 6

SE30 B3–15

83.4 ± 6

8753.6 ± 39

115.1 ± 3

1598.3 ± 29

116.6 ± 2

SE30 B3–20

88.6 ± 5

8956.4 ± 30

117.31 ± 4

1623.5 ± 32

106.6 ± 2

D—DGEBA, SE30 —Soy base epoxy 30 wt.%, B—Bismaleimide B1 (BMI-1)-N,N' -bismaleimido-4,4' -diphenyl methane B2 (BMI-2)-1,3-bis(maleimido) benzene B3 (BMI-3)-3,3' -bis(maleimidophenyl)phenylphosphine oxide (Understanding Composition of the system from sample code (e.g.) SE30 B1–5 —soy based epoxy (30 wt.%)—BMI-1 (5 wt.%))

when compared to BMI-1 and BMI-3 due to higher number of reactive molecules available due to its lower molecular weight which results in the formation of highly cross linked network. Tensile modulus values exhibited similar trends as in the case of tensile strength [25]. Similarly, addition of bismaleimides in to the soy based epoxy system improves the rigidity and as a result flexural strength and flexural modulus enhances. Among the bismaleimides modified soy based epoxy system BMI-2 modified system exhibits higher values of flexural strength and modulus than those of BMI-1 and BMI-3 modified systems. For example 5, 10, 15 and 20 wt.% addition of BMI-2 in the 30 wt.% soy based epoxy system increased the flexural strength upto 22.3%, 23.6%, 29.6% and 31.3% respectively. The flexural strength values for the same weight percentage of BMI-1 modified system are 18.6%, 20.8%, 26.2%, and 28.4% respectively, and for BMI-3 modified systems are 14%, 16.3%, 18% and 20.4% respectively. Similar trend is observed for the flexural modulus values of the bismaleimide modified systems [26].

Vegetable Oil Based Polymer Composites—Processing Properties …

35

The impact strength of the BMI modified soy based epoxy system decreases corresponding to the wt.% addition of different bismaleimides. The restricted chain mobility due to the formation of hetero aromatic bismaleimide rings is the cause for lowering the impact strength. Among the various bismaleimides the maximum reduction in impact values is exhibited by BMI-2 modified systems and is due to the attainment of higher cross-linking density. The morphology of the various bio based epoxy matrices were investigated by SEM is shown in Fig. 1. The SEM micrographs of unmodified neat DGEBA is smooth, glassy and homogeneous. Further, the neat soy epoxy exhibits homogeneous single-phase microstructure. The micrographs of 30 wt.% soy based epoxy matrix appeared with heterogeneous morphology and the rubbery phase is uniformly distributed throughout the matrix. The micrographs of different BMI modified 30 wt.% hybrid soy based epoxy matrices appear heterogeneous throughout. A smooth fracture surface is observed with increasing BMI content supports the brittle behavior [26].

5.2 BMI Modified Vegetable Oil Polymers for Flame Retardant Applications The flame retardant characteristics of vegetable oil based soy epoxy and various bismaleimide modified soy epoxy were analyzed with the char yield at 700 °C under air atmosphere and Limiting Oxygen Index (LOI) values. LOI is used for quantifying the flame retardancy of organic polymers. Materials exhibiting LOI above 21 might show flame retardant property. Generally, materials with LOI values higher than 26 would show self-extinguishing behaviour and were considered to be highly flame retardant [26]. The values of LOI and char yield for the soy based matrices and BMI modified soy based matrices are listed in Table 2. The char yield of the Bismaleimides modified hybrid matrices improves based on the nature and weight percent addition of different bismaleimides and imparts flame retardancy to the matrix. When compared to BMI-1 and BMI-2, the phosphorous containing bismaleimide (BMI-3) imparts better char yield and flame retardancy. The formation of oxidized layer upon burning the hybrid matrices serves as a barrier for the diffusion of oxygen and improves the flame retardancy. The BMI-3 increases the LOI values of the soy based epoxy from 22 to 29.85. Thus the phosphorous containing bismaleimide imparts excellent flame retardancy to the triglyceride based epoxy materials [26].

36

A. S. M.

Fig. 1 SEM images of a neat DGEBA b neat soy epoxy c soy based epoxy (30 wt.%) d BMI I modified e BMI II modified f BMI III modified hybrid soy based epoxy matrices

Vegetable Oil Based Polymer Composites—Processing Properties …

37

Table 2 Thermal stability and flame retardancy of bismaleimide hybrid soy based epoxy matrices Sample code

TGA analysis data Under N2

LOI Under air

50 wt.% loss (°C)

Char yield at 700 °C (wt.%)

50 wt.% loss (°C)

Char Yield at 700 °C (wt.%)

SE30

558

16.25

523

11.25

21.00

SE30 B1–5

510

17.15

490

12.25

22.4

SE30 B1–10

520

18.75

508

13.75

23.9

SE30 B1–15

538

22.25

513

17.25

24.4

SE30 B1–20

550

24.65

520

19.65

25.36

SE30 B2–5

525

16.25

494

11.25

22.0

SE30 B2–10

538

18.75

510

13.75

24.60

SE30 B2–15

540

21.87

520

16.87

25.24

SE30 B2–20

556

22.65

532

17.05

24.32

SE30 B3–5

540

28.4

513

17.50

23.2

SE30 B3–10

544

30.3

521

22.50

26.4

SE30 B3–15

550

32.9

533

24.62

24.55

SE30 B3–20

563

37.4

542

29.85

30.15

SE30 —Soy based Epoxy (30 wt.%); B—Bismaleimide B1 (BMI-1)-N, N' -bismaleimido-4,4' -diphenyl methane B2 (BMI-2)-1,3-bis(maleimido) benzene B3 (BMI-3)-3,3' -bis(maleimido phenyl) phenyl phosphine oxide (Understanding the Composition of systems from sample code (e.g.) SE30 B1–5 —means Soy based epoxy (30 wt.%)–BMI-1 (5 wt.%))

6 Conclusion Vegetable oils are abundant natural resource are yet to be fully utilized as a source in the preparation of polymeric composite materials for the sustainable future. Functionalization of vegetable oils results in several monomers that help in the preparation of variety of polymeric materials. However, these triglyceride based polymeric materials are weak and elastomeric in nature due to the presence of long aliphatic chains in the matrix. Blending of functionalized vegetable oils with petroleum based resins and subsequent modification with heteroaromatic bismaleimides offers a significant solution to the problem. The tensile and flexural strength of the bismaleimide modified soy based epoxy matrices significantly improved depending on the molecular weight and structure of the bismaleimides chosen. Similarly the results of TGA analysis and LOI values indicate rapid increase in the thermal stability and flame retardant characteristics. The phosphorous containing bismaleimides imparts better flame retardant characteristics to this hybrid soy based epoxy matrices. The utilization of epoxidized vegetable oils in the preparation of hybrid polymer matrices sets a foundation for the development of completely new materials for high performance

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Fig. 2 Images of (A) DGEBA (100%) (B) soy epoxy (100%) (C) soy based epoxy 30 wt.% (D) BMI-1 hybrid soy epoxy (E) BMI-2 hybrid soy epoxy (F) BMI-3 hybrid soy epoxy matrices

applications. This not only reduces the resource demand for the petro based materials but helps in the production of new composite materials for the sustainable future (see Fig. 2). (Neat DGEBA epoxy is transparent, neat soy epoxy and soy based epoxy matrices are translucent, BMI modified hybrid soy epoxy matrices are opaque and rigid) (see Figs. 3 and 4).

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Fig. 3 Photograph showing the flexible nature of soy epoxy matrix (100%)

Fig. 4 Photograph showing the elastomeric and translucent nature of neat soyepoxy matrix (100%)

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References 1. https://www.statista.com/statistics/263978/global-vegetable-oil-production-since-2000-2001/ 2. Frank RC, Luc P, Arnaldo WA (Oct 2009) Global overview of vegetable oils with reference to biodiesel; A report for the IEA bioenergy task 40, UK, Imperial College 3. Xu JY, Liu ZS, Erhan SZ, Carrier CJ (2002) A potential biodegradable rubber-viscoelastic properties of soybean oil based composites. J Am Oil Chem Soc 79:593–596 4. Yusof B (2002) Palm oil and its global supply and demand prospects. Oil Palm Indust Econ J 2:1–10 5. Zoran S (2002) Petrovic, Epoxidation of soybean oil in toluene with peroxoacetic and peroxoformic acids—kinetics and side reactions. Eur J Lipid Sci Technol 104:293–299 6. Park S-J (2004) Synthesis and thermal properties of epoxidized vegetable oil. Macromol Rapid Commun 25:724–727 7. Park SJ, Jin FL, Lee JR (2004) Effect of biodegradable epoxidized castor oil on physicochemical and mechanical properties of epoxy resins. Macromol Chem Phys 205:2048–2054 8. Khot SN, La Scala JJ, Can E, Morye SS, Williams GJ, Palmese GR, Kusefoglu SH, Wool RP (2001) Development and application of triglyceride based polymers and composites. J Appl Polym Sci 82:703–723 9. Zlatanic A (2004) Effect of structure on properties of polyols and polyurethanes based on different vegetable oils. J Polym Sci Part B Polym Phys 42:809–819 10. Guo A (2002) Polyols and polyurethanes from hydroformylation of soybean oil. J Polym Environ 10:112 11. Part A (2000) Structure and properties of halogenated and non halogenated soy based polyol, Andrew Guo. J Polym Sci Polym Chem 38:3900–3910 12. Latere Dwan’Isa JP, Mohanty AK, Misra M, Drzal LT, Kazemizadeh M (2003) Novel biobased polyurethane synthesized from soybean phosphate ester polyols; thermomechanical properties evaluations. J Polym Environ 11:161–168 13. Guo A, Cho Y, Petrovic ZS (2000) Structure and properties of halogenated and nonhalogenated soy based polyols. J Polym Sci Part A Polym Chem 38:3900–3910 14. Miao S, Callow N, Wang P, Liu Y, Su Z, Zhang S (2013) Soybean oil-based polyurethane networks: shape-memory effects and surface morphologies. J Am Oil Chem Soc. https://doi. org/10.1007/s11746-013-2273-5 15. Sienkiewicz A, Czub P (2017) Novel bio-based epoxy-polyurethane materials from modified vegetable oils—synthesis and characterization, Express Polym Lett 11(4):308–319 16. Miao S, Sun L, Wang P, Liu R, Su Z, Zhang S (2012) Soybean oil based polyurethane networks as candidate biomaterials: synthesis and biocompatibility. Eur J Lipid Sci Tech 114:1165–1174 17. Fernandes FC, Kirwan K, Wilson PR, Coles SR (2019) Sustainable alternative composites using waste vegetable oil based resins. J Polym Environ 27:2464–2477 18. Athawale VD, Pillay PS (2003) Interpenetrating polymer networks of uralkyd resin based on hydrogeneated castor oil and poly(butyl acrylate). J Macromol Sci: Part A—Pure Appl Chem A40:1227–1240 19. Wold CR, Soucek MD (2000) Viscoelastic and thermal properties of linseed oil-based creamer coatings. Macromol Chem Phys 201:382–392 20. Yan S, Lian G (2005) Synthesis and characterization of phase controllable ZrO2 and carbon nanotube composites. Nanotechnology 16:625–630 21. Park SJ, Jin FL, Lee JR (2004) Synthesis and thermal properties of epoxidized vegetable oils. Macromol Rapid Commun 25:724–727 22. Ratna D (2001) Mechanical properties and morphology of epoxidized soybean oil modified epoxy resin. Polym Int 50:179–184 23. Miyagawa H, Misra M, Drazal LT (2005) Fracture toughness and impact strength of anhydride cured biobased epoxy. Polym Eng Sci 45:487–495 24. Dinakaran K, Suresh KR, Alagar M (2003) Preparation and characterization of bismaleimide modified bisphenol dicyanate epoxy matrices. J Appl Polym Sci 90:1596–1603

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25. Aboobucker Sithique M, Ramesh S, Alagar M (2008) Mechanical and morphological behaviour of bismaleimide modified soy-based epoxy matrices. Int J Polym Mater 57:480–493 26. Liu YL, Chiu YC, Wu CS (2003) Preparation of silicon-phosphorous containing epoxy resins from the fusion process to bring a synergistic effect on improving the resins, thermal stability and flame retardancy. J Appl Polym Sci 87:404–411

Olive Oil Based Composites Carlo Santulli, Mirajul Alam Sarker, and Md Enamul Hoque

Abstract The productive system of olive oil is able to offer various possibilities, in particular as regards the use of waste, for their introduction into composites. This can take place in the form of filler, such as it is in the case for olive mills residues e.g., olive pomace or olive husk, or for the production of bio-based resins, which can be obtained from epoxidation of vegetable oils. Further developments would also concern the use of ligno-cellulosic waste from olive oil production, which can suggest possible application in terms of wood-replacement materials, or as a source of crystalline cellulose.

1 Introduction The productive system based on olive oil is characterized by the non-avoidable creation of liquid and solid by-products, such as olive mill wastewater and olive husk. The connections between the olive oil production system and composite manufacturing can be considered twofold. As an initial remark, the system generates a large amount of waste of different characteristics, as discussed below, which is to be disposed, but in another sense represents a considerable possible source of outcome, in the case it is judiciously evaluated for its properties and potential. The system for evaluation of the amounts of olive waste from the production process is depicted in Fig. 1. The amounts of waste obtained does depend on which of the two main technologies for the purpose is used in olive processing, namely batch-pressure or continuouscentrifugation [2]. General amounts of olive waste can be used e.g., as low-price soil-stabilizing material, after burning at 550 °C [3]. A more consistently described C. Santulli (B) Geology Division, School of Science and Technology, Università di Camerino, Via Gentile III da Varano 7, 62032 Camerino, Italy e-mail: [email protected] M. A. Sarker · M. E. Hoque Department of Biomedical Engineering, Military Institute of Science and Technology (MIST), Dhaka, Bangladesh © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 S. A. Bhawani et al. (eds.), Vegetable Oil-Based Composites, Composites Science and Technology, https://doi.org/10.1007/978-981-99-9959-0_3

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Fig. 1 Amounts of waste obtained from olive oil production system (redrawn from [1])

Fig. 2 Chemical components of olive oil and their groups

solid by-product is olive foot cake, which can be exhausted then by continuing the extraction of oil as far as technically or economically viable, after which the problem of disposal of the cakes is posed. The use of exhaust foot cake (EFC) as the substitute for high-sulfur combustibles, normally used in brick manufacture, has also received some attention [4]. In practice, thermal degradation of olive solid waste takes place in three consecutive phases i.e., drying, removal of volatile matters and char oxidation and waste diameter does influence the respective quantity of ashes and char [5]. Chemometric analysis of oil cakes did demonstrate that, while pH is very variable, on the other side the amount of carbon present does not change much, being around 55% [6]. However, this use of oil cakes in the present context does collide with environmental regulations, starting from EC 2008/98 directive, which imply that

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materials do need to be possibly maintained into the productive system, therefore possibly obtaining products for further use rather than just for energy recovery. In this context, the oil mill residue, which is referred to as “olive pomace” or “olive husk”, has recently found a number of possible applications, as from MedouniHaroune et al., 2018, suggested [7]. A significant issue with olive pomace is that it is not compostable and is phytotoxic due to its high contents in phenols [8]. This residue can be subjected to a second passage for extraction of further oil, in which case it can be considered exhausted pomace, or else it can be dried after the process that results in obtaining two types of waste material, olive flour from shells, and olive pits. From exhausted olive pomace, the extraction of antioxidants with moderate bactericidal action, such as phenols and flavonoids, has also been effectively carried out [9]. Section 2 concerns the different characteristics of olive oil, which are effectively related to the potential application of by-products from the productive system in the field of composites, especially for resin synthesis. In Sect. 3 the use of secondary raw products from oil is discussed, as it can represent an added value to the production of composites, due to these products representing a further justification to act on waste so to declassify it into secondary raw material, therefore approaching more effectively a circular economy approach. In Sect. 4, waste by-products from the oil system, such as olive pomace or nuts, when specifically used in composites as fillers, can be used as the filler for polymer matrices. More developed aspects are possible nonetheless with by-products from olive oil system. In particular, a more developed aspect is linked to the possibility to produce emulsion composite films including olive oil with other polysaccharide or triglyceride-based additives, therefore leading to the inclusion of olive oil amongst other oils used in the production of composites. This is less popular than the use of other oils for the production of resins, since the production of olive oil is strictly related to some specific regions, also for climatic reasons, such as the Mediterranean area (Sect. 5). However, significant results have been recently used for the production of bio-epoxy resins [10]. In practice, the most common vegetable oils used for the epoxidation are corn, cottonseed, crambe, linseed, peanut, rapeseed, safflower, sesame, soybean and sunflower [11].

2 Characteristics of Olive Oil 2.1 Chemical Properties Olive oil comprises about 200 different compounds [12] that include ~99% triacylglycerols (OOO, StOO, OOL, POL, POO, etc.) primarily and secondarily fatty acids (saturated fatty acids-SFAs, monounsaturated fatty acids-MUFAs, polyunsaturated fatty acids-PUFAs), and about 0.5–1.5% nonglyceride components (natural hydrocarbons, phenolic compounds, tocols, sterols, alcohols, tocopherols, carotenoids, etc.) [13]. However, these values can differ depending on pre and post-harvest factors,

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genetic, agronomic, environmental conditions, tree age, soil quality, the oil extraction process, storage type, and other related factors [14]. According to European Union Legislation, acidity in terms of oleic acid of various grades of olive oil are Extra virgin olive oil (≤0.8%), Virgin olive oil (≤2%), Refined olive oil (≤0.3%) and Lampante olive oil (>2%) (EU Reg. 2019/1604, 2019) [15]. The acidity range of the listed grades is the same, following the International Olive Council standard, except for Lampante virgin olive oil (>3.3%), as from the IOC Standards. Olive oil’s edibility decreases with the increase of acidity. Among fatty acids found in the oil, oleic acid (C18:1) −72.77%, palmitic acid (C16:0) −12.09%, linoleic acid (C18:2) −9.47%, stearic acid (C18:0) −3.01% and palmitoleic acid (C16:1) −1.15% is prevalent [16]. The other minor fatty acid concentrations are mentioned in Table 1. According to the U.S. Department of Agriculture, the total mass of SFAs, MUFAs, and PUFAs are 13.8 g, 73 g, and 10.5 g, respectively, present in 100 g of olive oil sample. Due to high levels of monounsaturated fats, it can be used as a healthy substitute for other shortenings like palm oil shortening, which needs extra effort to maintain a precise temperature (5 °C below the melting point) during its storage and transportation [17]. Moreover, higher dietary MUFAs intake was linked to a lower chance of stroke. A study has found that the risk of cerebrovascular illness is inversely correlated to the consumption of MUFAs [18]. Triacylglycerols, also known as triglycerides or triacylglycerides, are tri-esters of three fatty acid molecules bonded together by one glycerol molecule. OOO (40– 59%), LOO (12–20%), POO (12–20%), POL (6–7%), and StOO (3–7%) are the triacylglycerols present in a dominating amount in olive oil [19]. The lipid acid radicals linoleoyl, oleoyl, palmitoyl, and stearoyl are designated by L, O, P, and St, respectively. High-performance liquid chromatography (HPLC) that determines the number of triacylglycerols is used to assess the authenticity of olive oil. The oil holds a considerable quantity of α-tocopherol, the key constituent of vitamin E. Liposoluble antioxidants are significant in nature. Lipid peroxidation of cellular membrane and lipoproteins is effectively inhibited by tocopherols (vitamin E). They are also critical lipid-soluble antioxidants found in food, human and animal tissues, and tocols (tocopherols and tocotrienols) may have health benefits such as avoiding cancer, heart disease, and other chronic disorders [20]. Some secondary metabolites Table 1 Percentage of minor fatty acids of olive oil [16]

Fatty acid

Lipid number

Avg. value (% m/m)

Linolenic acid

C18:3

0.60

Arachidic acid

C20:0

0.36

Eicosenoic acid

C20:1

0.23

Behenic acid

C22:0

0.11

Margaroleic acid

C17:1

0.10

Margaric acid

C17:0

0.05

Lignoceric acid

C24:0

0.05

Myristic acid

C14:0

0.010

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are found in trace amounts in olive oil. Many of these are made up of phenolic compounds (allied phenolic, flavonoids, and polyphenolic compounds) that protect triacylglycerols from oxidation [21]. Typically, the overall amount of phenol contents has range from196 to 500 mg per kg [22]. The highest phenol content is obtained in extra virgin olive oil (EVOO), which has a range of 250.77 to 925.75 mg per kg [23]. There are at least 36 structurally different phenolic components found in olive oil, primarily grouped into five categories (acids, alcohols, secoiridoids, flavonoids, and lignans) [24]. Due to the presence of some phenolic compounds, like hydroxytyrosol and oleuropein, extra-virgin olive oil can help prevent or reverse liver damage by activating multiple signaling pathways in hepatocytes [25]. Furthermore, the oil components show antibacterial and antimicrobial properties against foodborne pathogens resulting in protection against different diseases [26]. Polycaprolactone (PCL) (with a favorable viscoelastic property and low melting temperature) based scaffold, which has a great potential in tissue engineering therapy [27, 28], can be modified with the help of extra virgin olive oil (EVOO) [29]. Moreover, olive oil is distinguished from other oils rich in MUFAs by the presence of phenolic compounds, carotenoids, chlorophylls, and hydrocarbons, which act as potent antioxidants. However, the present research suggests that biodiesel can be produced from olive oil [30], not dissimilarly from other vegetable oils, such as palm, soybean, and sunflower oil [31], as replacements for depleting fossil fuels (Fig. 2).

2.2 Physicochemical Properties To determine the physicochemical characteristics of olive oil, several essential parameters are available such as acid value (AV), phenol content, specific absorption coefficient (K232 , K270, and △K), refractive index, peroxide value (PV), anisidine value, saponification value (SV), ester value (EV), iodine value (IV), density, and viscosity. Olive oil is not soluble in water. So, its acidity is determined in terms of free fatty acid (FFA) value (as discussed earlier) rather than pH. On the other hand, acid value (AV) is the value of potassium hydroxide (KOH) in milligrams required to neutralize the fatty acids in one gram of the oil sample. Olive oil has an acid value (AV) of 4.23 mg KOH/g [32]. The oil stability during storage is mainly dependent on the phenolic content. It ranges from 168.53 to 137.22 mg/Kg at ambient temperature, from 168.53 to 165.78 mg/Kg at refrigerated temperature, in terms of gallic acid, and has a decreasing trend with respect to storage time, especially when stored at ambient or room temperature [33]. The formation of conjugated dienes is indicated by the specific absorption coefficient K232 , which has an absorbance of 232 nm UV rays. Likewise, K270 , with a 270 nm absorption, indicates triene conjugation and the presence of carbonylic substances. According to the European Union regulation 2019/ 1604, for extra virgin olive oil (EVOO), values of the specific absorption coefficients K232 , K270, and △K are ≤2.50, ≤0.22, and ≤0.01, respectively. Peroxide value (PV) is calculated in milliequivalent (mEq) of active O2 present in per kilogram of the oil. This value cannot exceed 20 mEq O2 /kg for EVOO and VOO. It represents the

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total hydroperoxide (HP) content. As the consequence, high PV implies equally high HP contents, which can further decompose into volatile and non-volatile chemicals, which eventually leads to rancidity of the oil [34]. Similarly, the anisidine value is used to measure the secondary oxidation components, such as 2-alkenals and 2, 4alkadienals created as a result of hydroperoxide decomposition, and it shows extra sensitivity to unsaturated aldehydes [19]. Saponification value (SV) is the amount of potassium hydroxide (KOH), or potash, needed to neutralize the free fatty acids (FFAs) and saponify the esters in a gram of oil measured in milligram. This value ranges from 184 to 196 mg KOH/g oil. However, the ester value (EV) is the amount in milligrams of potassium hydroxide (KOH) needed to hydrolyze the esters contained in a gram of oil sample. So, this value is determined by subtracting acid value (AV) from saponification value (SV). EV of olive oil is 190.86 mg KOH/g [19]. Iodine number (IV) represents the unsaturation of olive oil. It is defined as the amount of iodine required in terms of grams to saturate the fatty acids that exist in 100 g of oil. This value ranges from 75 to 94/100 g. Refractive index, density and viscosity of olive oil are 1.464, 0.906 mg/mL and 47.4 cP respectively [35]. Possible chances of the development of rancidity in the oil can be identified by the refractive index.

2.3 Organoleptic Characteristics Organoleptic, also known as sensory properties, is a significant technique to characterize olive oil and analyze consumer preferences. The oil has a wide range of sensory characteristics, with fruitiness, bitterness, and pungency being the most prominent. Though it is tough to generalize these properties through some definite standardized terminologies as they vary on different factors like-variety, ripening degree, environmental and climate conditions, harvesting system, geographical location, and oil extraction processes [36], some acceptable testing methods have been developed in this regard. Among those, the “COI Panel test,” a standardized sensory technique for virgin olive oils, is the most useful approach to evaluate the sensory qualities of the oil. This worldwide technique aims to standardize processes for analyzing VOO’s organoleptic qualities and to produce a grading system. This approach, adopted into European Union rules in 1991, involves a group of 8–12 people who are appropriately trained to recognize and assess the severity of positive and negative sensations as an analytical tool (EEC Reg. 2568/91, 1991) [37]. The International Olive Oil Council (IOC) has also devised procedures and guidelines for the sensory assessment of olive oils. The standards published by IOC (COI/T.20/Doc. No 4/Rev. 1 September 2007 and COI/T.20/Doc. No 15/Rev. 10 2018, and Trade Standards, 2021) include a set of general terminologies to be used by the tasters and methodology to assess the organoleptic characteristics of the oil [38–40]. The negative attributes or defects the tasters have to assess are fusty, winey or vinegary, metallic, muddy sediment, mustiness or humidity, rancid, and others. On a contrary, the only three positive attributes are fruity, pungent, and bitter. Previously, a prefixed score from number 0 to number 5 (1—Barely perceptible, 2—slight perceptible, 3—average, 4—great,

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and 5—extreme) was given to evaluate each of these sensations. Now, a continuous scale of 0 to 10 cm is used for this purpose, allowing the tasters freely assess each of the attributes (positive and negative). Olive oils can be classified through the median of defects and median of attributes. EVOO has a median of defects = 0 and median of fruity attribute >0, VOO has a median of defects ≤3.5 and median of fruity attribute >0. In contrast, “lampante” virgin olive oil, obtained without any treatment other than by mechanical and thermal means has a median of defects >3.5 or the median of defects ≤3.5, and median of fruity attribute = 0. Among the median of “bitter” and “pungent” attribute, if the value of either or both of them exceed 5, it is mentioned in the test certificate [15]. There is a bunch of chemical components subjected to the sensational characteristics of olive oil. Phenolic compounds act as not only antioxidants, but also are also responsible for bitter and pungent tastes of the oil. The correlation coefficient, r = 0.69 for total phenol contents (TPC) and bitterness, r = 0.54 for TPC and pungency, and particularly for 3,4-DHPEA-EA and bitterness, r = 0.57 are found in contemporary studies [41]. However, a high level of phenolic compounds affects both positive and negative sensory properties. A high concentration of these components results in about a 39% decrease in fruitiness, a 23% decrease in fusty/muddy defect, and a 733% increase in winey/vinegary defect [42]. Olive oil gets its fruitiness from freshly extracted olives that are neither green nor ripe. The odor-active chemicals emerging from the LOX pathway are primarily responsible for the fruitiness of extra virgin olive oil [43]. Moreover, rancidity, a negative sensation of the oil, is due to the high amount of the volatile organic compounds, which are mostly unpleasant aldehydes derived from the oxidation of unsaturated fatty acids during storage [44]. However, some other factors like storage defects, processing & extraction defects etc., cause the formation of different VOCs, yeasts, alcohols, eaters, etc., which lead to various negative sensations.

3 The Productive System of Olive Oil: Use of Secondary Raw Products from Oil This section concerns the secondary products from oil and the prospected and actual application of waste from the oil production system that do not include the use in composites, dealt with in Sects. 4 and 5, yet can go alongside these, contributing in some cases to the success of evolving the productive system towards conditions closer to circular economy. Apart from the well-known food-related uses of olive oil, other traditional applications are in the field of medicine or cosmetics, such as for relieving burns and cleansing skin, and in the production of Marseille soap [45]. In general terms, potential and challenges are reported in the possibility to use olive by-products and waste for the development of cosmetics, in particular over the presence of bioactive substance and the relevant facility of extraction, such as it is reported in Fig. 3 [46].

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Fig. 3 Strengths (S)—weakness (W)—opportunities (O)—threats (T) diagram related to the development of cosmetics containing olive by-products active components [46]

As regards waste from oil, some of it can be composted in industrial conditions, or at least mixed with soil in safe conditions. In this case, a few possible applications are possible, such as an amending agent in agriculture, provided nitrogen and phosphorus tenor is sufficient [47], bio-fertilizer for home applications, such as with foliagepotted plants [48], and for contribution to bioremediation by the removal of toxic metals, such as lead and cadmium, especially at pH between 4 and 7 [49]. Another possibility is the use of olive stones for the production on activated carbons applied as adsorbents [50]. In particular, olive pomace can also be used for biosorbent activity over heavy metals: two different extraction procedures were compared, involving either methanol or hexane followed by methanol, for copper and cadmium removal [51]. Also, wastewater from oil mill processing, rich in natural antioxidants, such as phenols [52], was proposed in a revalorization process for the fabrication of antibacterial packaging items for the natural antioxidants, such as phenols, present in this waste [53].

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4 Use of Waste By-Products from the Olive Oil System in Composites The use of waste from oil productive system in composites can be considered of more general purpose than other uses, which provide, at the expense of the yield obtained, a more crystalline, hence valuable material, such as the possibility to develop cellulose nanocrystals from oil waste, which was recently proposed [54]. On the other side, the limited discard rate obtained from olive oil waste in the production of composites can be considered positive when striving to approach circular economy. In the case of the use of lignocellulosic waste products from oil production system, such as olive shell flour (OSF) or olive pomace (OP), the principal question appears to be to ensure a sufficient compatibility between the filler and the polymer matrix. This of course starts from the assumption that a petrochemical matrix, therefore hydrophobic is used, hence achieving a sufficiently strong interface might not be obvious. In practice, the use of olive stones as the filler of composites has been the object of a specific recent review [55]. The profile of use might be even higher in a concept of production of wood-replacement particleboards even for interior design applications [56]. Technically, olive stones and olive shells are not exactly synonyms, in the sense that the stone is composed by the seed and its wood shell, although in practice they are used in polymers in a powdered form. The difference in composition between the entire olive stone and the bare seed husk is limited, and it can be considered that the three main components, hence hemicellulose, cellulose and lignin, are present in similar amounts, with a slight predominance of cellulose [57]. Valvez et al. illustrated the fact that a large number of matrices, both thermoplastic and thermosetting, have been employed when including OSF as filler. It is notable that the viscosity obtainable in thermoplastic matrices, such as polypropylene, after filling with OSF, is still suitable for injection, in the same way that it is for common fillers, such as e.g., calcium carbonate. Olive shell flour (OSF) from exocarp (skin) and mesocarp (pulp) as residues of olive oil production has been introduced into a polyethylene matrix in an amount of up to 50 wt.% using a maleic anhydride equivalent coupling agent [58]. This procedure was intended to offer the possibility of composites fabrication under compression molding and extrusion, however, despite the presence of the coupling agent, interfacial adhesion represented a problem. The same amount of OSF was also introduced in a poly(vinyl chloride) (PVC) through melt compounding and injection molding, with positive effect on composite stiffness, though at the expense of some of the mechanical strength and with a water absorption of around 7% at saturation [59]. Through maleinization, it was even possible to add 60 wt.% of OSF to a polypropylene matrix with a positive effect on tensile and flexural modulus, while the limited improvement of tensile strength was attributed to the low aspect ratio averaging at 4.4 [60]. One important factor is the necessity to grind olive pits to a shape that can allow a sufficient amount of them to be introduced in the resin. Coming down to dimensions of 10–30 μm, the introduction of up to 44 wt.% OSF was possible into epoxy

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resins, which enabled obtaining an increase of flexural modulus of 48%, substantially unaffected by thermal cycling at a maximum temperature of 80 °C [61]. As regards thermal properties of biopolymers, introducing OSF into poly(lactic acid) (PLA) does not significantly modify glass transition temperature and thermal degradation profile of the polymer, whilst promoting its cold crystallization [62]. The extent of the compatibilization issue has been revealed to be more limited in the case of composites including OSF in unsaturated polyester matrix, where the adapted application of a mercaptosilane treatment and the use of a compression molding manufacturing process allowed a considerable reduction of sensitivity to water absorption [63]. When using biopolymers, such as poly(lactic acid) (PLA), tensile strength and stiffness can be improved by the addition of up to 20 wt.% of olive pits in powder form, although the mode of grinding, whether centrifugal or planetary, can considerably affect the properties, taking into account the large variation of pits powder geometries obtained [64]. In the case of olive pomace (OP), early attempts concentrated on the possible use as the filler in polypropylene (PP), in particular as a ligneous replacement for wood flour, suggesting also its use in fiberglass/PP composites [65]. To increase the possible range of polymers to which this could be applicable, the question of pomace treatment by chemical agents was also posed. Namely, it was noticed that the benzoylation treatment on this lignocellulosic waste enabled its successful introduction into a poly(vinylchloride) (PVC) matrix, up to 25 wt.%, improving both elongation and strength of the composite: dielectric tests at 100 Hz frequency also indicated some potential for application of this composite in insulators [66]. In contrast, no compatibilization was needed in the case of olive pomace-polypropylene composites, when the addition of up to 40 wt.% of OP offered and increase in tensile and flexural stiffness of 62.5% and 19%, respectively [67]. The storage modulus and the thermal stability were progressively enhanced with OP weight fraction, although, as reported in Fig. 4, it is also suggested that the maximum effect of loss by relaxation was always revealed at 80 °C, on which the effect of OP addition can be considered negligible.

Fig. 4 Storage modulus (left) and loss modulus (right) of olive pomace-polypropylene composites [68]

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A recent review reports on different potential applications for olive pomace after drying and destoning, especially as food additive: on the other side, the high content of fibers and phenols might suggest further uses in the field of materials and resins [69].

5 Production of Resins Including Olive Oil A number of works have also been dedicated to the production of films, especially aimed at food packaging, which include olive oil in combination with proteins or polysaccharides. It is well known as olive oil addition does increase considerably the water vapor barrier properties together with offering improving other properties, such as tensile strength. This has for example been ascertained in the case of corn starch films aimed at edible packaging, where an addition of up to 10 wt.% of olive oil was able to more than double tensile performance together with reducing by several times water vapor penetration [70]. The production of composite films including was carried out using bovine gelatin in combination with glycerol and olive oil: the result was rather deceptive for mechanical strength and extensibility. Despite the films not being transparent, their potential application was due to water and vapor barrier ability, as recognized also previously in the case of films produced from pectin and gelatin/sodium alginate blends with 2.5 and 5% added olive oil [71]. These characteristics are coupled with an increase in the glass transition temperature of bovine gelatin (normally 61 °C) by the addition of olive oil [72]. Considering polysaccharides, homogeneous and translucent edible films were obtained using chitosan in combination with up to 15 wt.% olive oil, where the progressive addition of olive oil above 5 wt.% increased the thickness from around 70 to 95 microns and also slightly enhanced the contact angle from 60 to 65° [73]. This resulted in an improvement of average tensile properties from 8.52 to 14.69 MPa, passing from 5 to 15 wt.% of olive oil, whilst the blending of just 5 wt.% of olive oil proved rather ineffective for the purpose. Olive oil was also intended as a compatibilizing agent for the improvement of the properties of microcrystalline cellulose (MCC)—poly(lactic acid (PLA) films through a transesterification reaction between MCC and olive oil at 110 °C for 90 min [74]. This is in practice a reaction between a triglyceride and an alcohol in the presence of a strong acid or base [75]. In this way, beyond obtaining lower moisture absorption, also a slightly increased crystallinity than pure PLA was achieved, without compromising the biodegradability of the films.

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6 Conclusions Olive oil, for its abundant production, together with the variety of materials obtained as by-products or waste, is a possible candidate for the manufacturing of biocomposites, in a moment in which approaching circular economy does require the need for reducing to a minimum the amount of unprocessed and discarded waste. Of course, the abundance of lignocellulosic materials in this system often suggests their application in terms of energy recovery rather than bringing them back into the production system. A possibility in this regard is the production of bio-based resins, in which olive oil has many competitors from other food and non-food centered systems, examples of which are soy, sunflower, castor oil or palm oil. On the other side, its organoleptic characteristics, which suggests its use into cosmetic productive system, allows olive oil resins entering also some food related fields, such as the one for sustainable food packaging.

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Canola Oil as a Bio-additive: Properties, Processing and Applications Farzana Ahmad, Sohail Abbas, Amina Bibi, Mohammad Luqman, and Muhammad Jamil

Abstract In recent years, vegetables and plant-based edible oils have received a lot of attention owing to the presence of high amounts of mono-, and polyunsaturated fatty acids (MUFA, and PUFA) in a balanced diet, and their various domestic and industrial applications. Canola oil is a kind of vegetable oil derived from rapeseed. Canola (rapeseed) is the world’s third-largest oilseed crop, trailing behind only soybean and cottonseed. It contains a smaller amount of non-polymerizing saturated fatty acids, which means it has superior edible characteristics. Further, it contains 6–14% α-linolenic acid, 50–65% oleic acid, and 7% saturated fatty acids. It also contains omega-3 and omega-6 fatty acids, making it one of the most useful cooking oils in the market. Canola oil contains a high amount of vitamins K and E, and it helps to reduce skin issues and indications of aging such as acne, fine lines, wrinkles, blemishes, and spots. It shows strong physico-chemical and function properties. This chapter reviews and addresses the availability (production and consumption), physico-chemical and functional properties of canola oil as an additive which facilitate its application in various fields including composites and coatings, biodiesel production, and food. It also discusses about canola oil refining and its processing, nutritional properties, and health benefits. This up-to-date review will be very helpful F. Ahmad Department of Chemistry, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea S. Abbas Department of Geography, Konkuk University, Seoul 05029, Korea A. Bibi Punjab Food Authority, Sheenbagh, Attock, Punjab, Pakistan M. Luqman (B) Chemical Engineering Department, College of Engineering, Taibah University, Yanbu Al-Bahr Campus, Yanbu 41911, Kingdom of Saudi Arabia e-mail: [email protected] M. Jamil (B) Sang-Ho College of Libral Arts, Konkuk University, Seoul 05029, Korea e-mail: [email protected] Department of Physics, Konkuk University, Seoul 05029, Korea © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 S. A. Bhawani et al. (eds.), Vegetable Oil-Based Composites, Composites Science and Technology, https://doi.org/10.1007/978-981-99-9959-0_4

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in selecting and using canola oil effectively and in a sustainable manner for various domestic and industrial applications including in biocomposites. Keywords Canola oil · Additive · Biocomposites · Chemical and physical properties · Biodiesel · Food · Coatings · Omega fatty acids · Edible · Healthy

1 Introduction Vegetable/edible oils are obtained from various types of plants (but mainly from their fruits and seeds), vegetables and nuts. These serve as the major source of mono-, and poly-unsaturated fatty acids (MUFA, and PUFA, respectively) in the diet. However, oils based on the palm, cocoa and coconut are the three important sources of saturated fatty acids (SFA) [1]. Oils extracted from olives, almonds, walnuts, flax and sesame seeds are in use for over 6000 years for numerous important purposes. The first/oldest vegetable oil which have been used by the humanity is probably the Olive oil as its residues were found from excavations in Tunis, and in large clay utensils in Crete (in Minoan palaces) [1]. Figure 1 shows the per capita worldwide total supply of commercially important (specific and general) vegetable oils for the last 50 years. It is clearly shown in the figure that the supply of these oils (kcal per capita per day) had been increased over two folds during this period, mainly owing to the increased supply of soybean, sunflower, mustard, rape and palm oils [1]. Vegetable oils are usually extracted from plant components mainly seeds by mechanical cold crushing or cold pressing using a mill/an expeller, or chemical extraction using solvents. A few oils including virgin/extra virgin olive oils, are extracted by mechanically pressing the seeds under controlled temperatures without any further treatment and used as such. However, owing to the presence of a few percentages of undesirable or bit harmful components including oxidized materials and free acids, and to modify the color, odor and taste, majority of vegetable oils are refined to some extent. Refining process leads an improvement in terms of a longer shelf life, appearance, smell, and taste of the edible oils. However, as a result of refining process, the composition of fatty acids of these oils gets altered. Coldpressing the olive and other vegetable oils including sunflower oil leads to a decrease in linoleic acid (LA)/alpha-linolenic acid (ALA) ratio, and an increase in the amount of oleic acid (OA) in comparison to those which have been refined. A schematic view of the three important acids (OA, LA, and ALA) can be seen in Fig. 2 [3a–b]. Interestingly, b-carotene, usually, can be found in cold-pressed oils while it is missing in the refined ones. The major component of vegetable oils is triacylglycerols; esters of fatty acids with glycerols. The other components in lower amounts are mono- and di-acylglycerols, and non-glyceridic nutrients and free fatty acids. These oils vary in their composition of fatty acids, and most of these oils are high in MUFA and/or PUFA or both, whereas

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Fig. 1 Supply (kcal capita−1 day−1 ) of vegetable oils worldwide during 1961 to 2011 [1, 2]

Fig. 2 A view of the oleic acid, linoleic acid and linolenic acid [3]

three (e.g. palm, cocoa and coconut) of them are high in SFA. Earlier generations were very much dependent on animal fats/oils. With the advent of extraction technologies, there is a significant increase in the consumption of vegetable oils during the last 150 years which contributed as probably the most important factor in the increase

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of dietary omega-6-to-omega-3 fatty acids ratio to its present value of 20 to 30 in comparison to a ratio of 2 in the diets of hunters [1]. The composition of fatty acids in vegetable oils depends on many factors including soil, climate, genetics of the plant, plant, fruit or seed maturity, and level of refining. It would be worthy to note that the processed edible oils, especially the partially hydrogenated ones, also contain noticeable amounts of total fatty acids (TFA). The composition of important vegetable oils in terms of MUFAs, PUFAs, and SFAs, and the essential LA and ALA is presented in Table 1 [1]. This table does not include the mixture of vegetable oils or those for industrial applications. It is clear from Table 1 that certain vegetable oils including those from Palm, Coconut, Cupu assu and Babassu, the range of SFAs start from 49 to 86%, which is even higher than those from the fats of beef and pork. Oils from Olive, Hazelnut and Avocado are higher in MUFA in addition to the high-oleic Safflower and Sunflower oils. The PUFAs’ composition in vegetable oils changes significantly, but the more desirable ones in terms of LA/ALA ratio are cold-pressed mustard (2.6), canola (2.1), and flaxseed oils (0.3) [1]. The worldwide vegetable oils’ production for 2020/2021 was 209.14 million metric tons in total [4]. As can be seen from the Fig. 3 [4], the top four oilseed crops based on their worldwide consumption in million metric tons are Palm (75.45), Soybean (59.48), Canola (27.64) and Sunflower-seed (19.02), respectively [5]. Canola crop originated in Canada, and this tradename is derived from the ‘Canada’ and ‘ola’ for oil. Canola plant belongs to the Brassicaceae (Cruciferae) family comprising almost 350 genera, and 3000 species [6]. Canola oil is considered as on one of the healthiest edible oils owing to its fatty acid content, with 60% OA (C18:1), 20% LA (C18:2), and 10% ALA (C18:3) (Table 2 [6]). With 10% of ALA content, it makes this oil an excellent source of ALA with a desirable ratio of 2:1 of LA (omega-6; ω-6) to ALA (omega-3; ω-3). This oil contains the least amount of saturated fatty acid with 7% or less as compared to that of sunflower oil (12%). Studies suggest that the diets which include canola oil could decrease the cholesterol levels of blood, and decrease the risk of cardiovascular diseases. This oil is also being used as cooking oil and to produce different kinds of Salad dressing by food manufacturers. Margarines with canola oil is also available at local food markets and being used for baking by processors [6]. If an oil is labeled “Canola”; which is a type of rapeseed oil, it must contain very low percentage of (less than 2%) Erucic acid and less than 30 micromoles of glucosinolates. Low Erucic Acid (LEA) rapeseed trade data are presented in Table 3 [6]. A sample of canola flower and canola oil can be seen in Fig. 4 [7]. These days, owing to great health awareness and concerns, it is mandatory to label the type and amount of trans-fatty acids in food products, thus, canola oil producers are growing different varieties having high-stability oils with ALA content lesser than 3%. The new varieties of oils have higher amounts of OA (ca. 65 to 74% vs. ca. 60%) and lower amounts of ALA (ca. 1 to 3% vs. ca. 10%) than the conventional one. Oils with high stability are especially useful for frying purposes where a high temperature and more than one time use of the same oil is needed. This allows the elimination or reduction of traces of trans-fatty acids from foods which makes these

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Table 1 Fatty acid composition of vegetable oils (g/100 g of vegetable oils) [1] Oil Grams/100 g Almond oil

Total SFA 8.2

Total MUFA

Total PUFA

LA

ALA

69.9

17.4

17.4

0.0

6.3

60.0

29.3

29.3

0.0

Apricot kernal oil

11.6

70.6

13.5

12.5

1.0

Avocado oil

81.2

11.4

1.6

1.6

0.0

Babassu oil

7.4

63.3

28.1

19.0

9.1

Canola oil

86.5

5.8

1.8

1.8

0.0

Coconut oil

25.9

51.9

51.5

0.2

Cottonseed oil

53.2

17.8

3.8

3.8

0.0

Cupu assu oil

9.0

38.7

67.8

14.3

53.4

Flaxseed oil

9.6

18.4

69.9

69.9

0.1

Grapseed oil

7.4

16.1

10.2

10.1

0.0

Hazelnut oil

11.6

78.0

21.2

15.3

5.9

Mustard oil

19.6

59.2

40.9

39.1

1.8

Oat oil

13.8

35.1

10.5

9.8

0.8

Olive oil

49.3

73.0

9.3

9.1

0.2

Palm oil

16.9

37.0

32.0

32.0

0.0

Peanut oil

13.5

46.2

62.4

62.4

0.0

Poppysead oil

18.7

19.7

35

33.4

1.6

Rice bran oil

7.5

39.3752

12.8

12.7

0.1

San flower oil. High oleic

6.2

14.3

74.6

74.6

0.0

Sau flower oil, Linoleic over 70%

14.2

39.7

41.7

41.3

0.3

Sesame oil

46.6

44

5.2

4.9

0.3

Shea nut oil

15.7

22.8

57.7

51.0

6.8

Soybean oil

9.9

83.7

3.8

3.6

0.2

Sunflower oil. Linoleic less than 60%

10.1

45.4

40.1

39.8

2.3

Tomato-seed oil

19.7

22.8

53.1

50.8

10.4

9.1

22.8

63.3

52.9

6.9

18.8

15.1

61.7

54.8

Walnut oil Wheat gram oil

food items healthier. Thus, these new varieties of oils are preferably used in industry for frying purposes [6]. The research related to canola oil and its composition has been conducted extensively throughout the world by many research groups. Here, in this chapter an overview of canola oil and its composition is provided, its basic and important properties, and various applications. Both fundamental and technological interest in canola oil arises primarily from their unique features. Therefore, the technical discussion is devoted primarily to canola oil composition, processing and its various application.

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Fig. 3 Worldwide consumption (in million metric tons) of vegetable oils from 2013–14 to 2020–21, by oil type [4]

Table 2 Details of world production and those of top five canola producing countries: from 2003–4 to 2012–13 (× 1000 tons) [6] Year

European Union

2003–04

11,214

Canada

China

India

Australia

World total

6771

11,420

6800

1703

39,464

2004–05

15,458

7673

13,182

6500

1542

46,144

2005–06

15,564

9483

13,052

7000

1419

48,589

2006–07

16,112

9000

10,966

5800

573

45,155

2007–08

18,397

9611

10,573

5450

1214

48,560

2008–09

19,062

12,644

12,100

6700

1844

57,971

2009–10

21,633

12,898

13,500

6400

1907

60,905

2010–11

20,300

12,789

12,900

7100

2359

59,891

2011–12

18,954

14,608

13,000

6200

3427

60,840

2012–13

19,300

13,310

12,900

6900

3898

61,626

In this chapter, we discuss some of the novel features related with canola oil and its and its composition. Additionally, some of the useful processing techniques are reviewed and canola oil applications and prospects are presented.

433

1388

2897

2284

2829

3485

2007–08

2008–09

2009–10

2010–11

2011–12

712

2006–07

224

2004–05

European community

2005–06

Year

2487

1100

2059

3085

855

954

713

362

China

2391

2337

2287

2061

2210

2170

2333

2277

Japan

Importing country

Table 3 Canola trade from 2004 to 2012 (× 1000 tons) [6]

1653

1492

1403

1077

1317

1065

1259

1196

Mexico

932

811

940

596

535

806

820

672

Pakistan

13,071

10,484

11,146

11,584

8648

7106

7521

5507

8680

7249

7315

7660

5916

5426

5846

3756

Canada

Exporting country World total

2486

1507

1172

1111

508

230

827

927

Australia

1341

1116

1910

2157

1496

755

357

160

Ukraine

13,071

10,484

11,146

11,584

8648

7106

7521

5507

World total

Canola Oil as a Bio-additive: Properties, Processing and Applications 65

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Fig. 4 A view of Canola flower and Canola oil [7]

2 Physico-chemical and Functional Properties of Canola Oil 2.1 Physico-chemical Properties The properties of all edible oils including canola oil are dictated by the composition (type and their amounts) of the oil in line with the standards for edible fats and oils. Important physical properties for canola oil and their comparison with those of high erucic acid rapeseed (HEAR) oil are presented in Table 4 [8]. Among vegetable oils, canola oil contains the least amount of saturated fatty acids which usually do not get polymerized which likely leads to better properties. The unsaturation level, i.e., number of double bonds per molecule, however, in canola oil is usually lesser than that in soybean or linseed oils [9]. The iodine value and saponification values are two very useful parameters for analyzing the quality of vegetable oils [10, 11]. A few important values are mentioned in Table 5 [10].

2.2 Functional Properties Canola oil is the third largest edible oil consumed worldwide. Almost 78% of canola oil produced in Canada (being its largest producer) was exported in 2019. It is being used in dressings, salad oils, baking shortenings, and soft and hard margarines. It

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Table 4 Physical properties of canola and rapeseed oils [8] Parameters value Canola Relative density (g

cm−3 :

20 °C/water at °C)

Refractive index (nD 40 °C) Crismer value mm2 s−1 )

HEAR

0.914–0.917

0.907–0.911

1.465–1.467

1.465–1.469

67–70

80–82

78.2

84.6

Cold test (15 h at 4 °C)

Passed

Passed

Smoke point (°C)

220–230

226–234

Viscosity (Kinematics at 20 °C,

Flash point, open cup (°C)

275–290

278–282

Specific heat (20 °C)

1.910–1.916

1.900–1.911

Saponification number

188–192

168–181

Iodine value

110–126

97–108

Table 5 Physical and chemical properties of vegetable oils [10] Properties

Soybean Sunflower Rapeseed Jojoba Jatroba Neem Castor Linseed oil

Kinematic viscosity @40 °C (cSt)

32.93

40.05

45.60

24.90

47.78

68.03

230.6

33.1

Kinematic 08.08 viscosity @100 °C (cSt)

9.02

8.65

06.43

08.04

10.14

19.72

–

Viscosity index 219

–

206

233

208

135

220

–

Saponofication 189 value (mg KOH g−1 )

–

–

94.69

196.80

166

180

190

Acid value (mg 0.61 KOH g−1 )

0.12

–

1.10

3.20

23.00

1.40

0.80

Iodine value

144

85

–

98.0

97

66.0

87

177

Flash point (°C)

240

–

252

–

240

–

250

–

can be used as a salad which usually remains clear at very low or refrigeration temperatures [12]. The high percentage of ALA (C18:3) in canola oil makes it very prone to oxidation. It is believed that the rate of oxidation depends on the number of double bonds in fatty acids; the higher the number of double bonds, the higher the rate of the oxidation. For example, the LA (C18:2) oxidizes ca. 25 times quicker than the OA (C18:1) [12]. The ALA (C18:3) having three double bonds oxidizes two times faster than that of LA. As a result, based on the need, ALA based oils including canola and soybean oils, are usually hydrogenated (adding hydrogen to double bonds to turn them into

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single bonds) lightly to saturate them. Consequently, this leads to an enhancement in the shelf and frying life of these oils by preventing/reducing oxidative rancidity. However, there is a drawback of this process. This not only saturates a few of existing cis-double bonds, but also leads to the formation of trans-fatty acids. The trans double bonds function similar to saturated bonds in that the oil can easily become solid with the help of newly produced saturated bonds, and newly produced trans-double bonds. The consumption of trans-fatty acids is recognized as unhealthy, thus this partial hydrogenation process has essentially been removed as an unsafe process for edible oils. A better alternative to this hydrogenation process is to find processes those may block the formation of ALA and/or trans fatty acids, and produce canola oil with lower levels of unsaturated fatty acids. Thus, in 2012, this led to the development of a much stable canola oil with high level of OA. This oil having excellent stability has now been used widely for deep frying, and as an ingredient in foods, by food industry in North America, at commercial levels. While OA accounts for 80% of the total fatty acids, LAs and ALAs account for ca. 23–27%, and ca. 3% for LA and ALA fatty acids in high OA based canola oil, respectively [12].

3 Canola Oil Composition and Its Advantageous Features Canola oil usually contains around 7% saturated fatty acids, 6–14% ALA, and 50– 65% OA. Cold pressed canola oil, on the other hand, has a greater concentration of tocopherols (60–70 mg/100 g) and phytosterols. In general, canola oil has a 1:2 ratio of a-tocopherols to g-tocopherols, and a 1:1 ratio of free to esterified phytosterols. It generally contains lower amounts of saturated fats and a linoleic to linolenic acid ratio of two to one (2, 1) [13–16]. Canola oil is the healthiest cooking oil since it includes both ω-3 and ω-6 fatty acids. Canola oil contains only around 7% of saturated fat, which aids in cholesterol reduction. It is high in vitamins K and E, and it helps with acne, fine lines, wrinkles, blemishes, and spots, as well as other skin issues and indications of aging. According to a research, people who utilized canola oil on a regular basis for almost a month lost their abdominal fat. Inflammation and joint stiffness are also reduced by canola oil [17]. Canola oil may offer health advantages, according to certain research, with some industry-funded studies stating that it is the healthiest oil available [18].

4 Canola Oil Refining and Processing The degummed crude oil is now refined to minimize/eliminate free fatty acids, any residual color bodies, phospholipids, copper and iron, and sulfur compounds in the case of canola oil. There are at least five key stages involved in the conventional alkali-refining process [12].

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4.1 Acid Pretreatment At the first stage, the degummed canola oil is heated to 50–60 °C, while simultaneously adding 300–2000 ppm of phosphoric acid into the oil and aggressively mixing it. The type of phospholipids which are nonhydratable can then be isolated once they have been acidified. The prooxidants copper and iron, along with Chlorophyll, are eliminated in addition to phospholipids [12].

4.2 Neutralization Sodium hydroxide as a neutralizing agent is usually used to determine the content of free fatty acid of the oil, and amount of phosphoric acid added to the oil. The amount of sodium hydroxide used will range between 8 and 12%. However, more alkali may be necessary to guarantee full saponification of these fatty acids. As a result, sodium hyaluronate hydrolyzes certain triacylglycerols. As a result, sodium hydroxide hydrolyzes certain triacylglycerols, resulting in soaps (fatty acid salts) and glycerol [12].

4.3 Removal of Soapstock Washing the soapstock out of the oil at 85–95 °C reduces the soapstock even more. To eliminate any residues of Soapstock, add citric or phosphoric acids to the residual oil [12].

4.4 Drying Oil It is performed by stirring the oil until it is totally dry at 105 °C [12].

4.5 Physical Refining Steam distillation is an alternative to alkali refining of oils for removing free fatty acids from it. After canola oil has been bleached and acid-degummed in a specifically constructed deodorizer, this process is carried out. It is more environmentally and process friendly than alkali/chemical refining since it avoids the manufacture of soap and the related disposal issues linked with the latter stage [12].

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4.6 Canola Oil Processing Canola oil is processed in a similar way to most edible oils, with the goal of removing potentially harmful small components. The ultimate aim is to create a TAG solution that is as pure as possible, similar to what is found in a bottle of edible oils purchased at the store [10]. Because one technique does not fit for all oilseeds, so canola oil along with all other edible oils, requires certain process changes. These distinctions are typically minor, but they are critical for the kind of oil processed [12].

5 Canola Oil Nutritional Properties and Health Benefits 5.1 Nutritional Properties Canola oil, like all dietary lipids, is a significant source of energy in diets [19]. It is recommended that lipids should account for between 10 and 35% of calories in an appropriate macronutrient distribution range (AMDR). In terms of particular fatty acids, the AMDR ranges from 5 to 10% for fatty acids (n-6), 0.6–1.2% of energy for ALA [19]. A higher level of canola oil consumption would assist most people in modifying their dietary fatty acid intake to be more in line with current dietary recommendations. It is documented in a report based on a modeling technique by National Health and Nutrition Examination Survey (NHANES) data of United States that if canola oil and food items (e.g. margarine) based on it is being used in place of commonly used edible oils and related items, U.S. adults would be healthier and in great compliance with dietary recommendations for MUFA/PUFA, saturated fatty acids, and ALA [20]. Saturated fatty acid consumption would drop by almost 9% if the replacement is done completely, bringing average consumption to slightly under almost 10%. Consumption of MUFA would increase by almost 28%, leading to an increase in the average consumption of MUFA to approximately 16%, while ALA would increase by almost 73% in this scenario [19]. These modifications would result in a 10% rise in those getting the recommended quantity of saturated fatty acids and a 20% increase in those ingesting the appropriate amount of ALA. The intake of LA may decrease as well, and the ratio of ω-6 to ω-63 fatty acids would drop from 10:1 to 3:1, a significant change [19]. There have been numerous claimed advantages of canola oil due to its composition. According to a study [21], canola oil contains the least amount of saturated fats when compared with popular edible oil, half that of olive and soybean oil, and is trans-fat free. When used as an alternative of saturated fat, around 1.5 teaspoons per day may keep the cardiologist away. Canola oil is also a rich source of vitamin E and has the most plant-based omega-3 fat of all the major cooking oils [21]. In fact, the US Food and Drug Administration even approved a qualified health claim for canola

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oil based on its ability to lower the risk of cardiovascular disease. Diabetes, renal health, and gastrointestinal health are all possible advantages [19]. There is a lot of concrete evidence demonstrating canola’s nutritional benefits, the majority of which is connected to heart health. Furthermore, based on the content of the oil, there is indirect evidence of nutritional effects [19]. Canola oil has a prominent role in the world’s kitchens, culinary items, and restaurants due to its low saturated fat content, good polyunsaturated and monounsaturated fat balance, flexibility, and light flavor [20]. A comparison of various dietary fats among various edible oils and food products can be seen in Fig. 5. Similarly, the nutritional analysis of the canola oil has been mentioned in Table 6 [22].

Fig. 5 A comparison of dietary fats among various edible oils [22]

Table 6 A view of the Canola oil nutritional analysis [22]. This analysis is based on two teaspoons (10 mL) of canola oil (refined)]

Nutritional analysis* Calories

80

Total fat

9g

Saturated fatty acids

0.5 g

Monounsaturated fatty acids

6g

Linoleic fatty acid (Omega-6)

1.5 g

Alpha-linolenic fatty acid (Omega-3)

0.6 g

Cholesterol (no trace)

0 mg

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5.2 Health Benefits Canola oil is a healthy choice because of its fatty acid composition, which is low in saturated fats and high in monounsaturated fats. Health specialists recommend lowering saturated fat in our diets and substituting it with mono or polyunsaturated fats to enhance heart health. It supplies a favorable ratio of omega-6 to omega-3 fatty acids as a great source of polyunsaturated fats [23]. A tablespoon of canola oil contains 1279 mg of omega-3s. According to the National Institutes of Health, omega-3 fatty acids may aid in the prevention of cardiovascular disease as well as other illnesses and disorders like Alzheimer’s, cancer, age-related macular degeneration, rheumatoid arthritis, and dry eye conditions [23]. Omega-6 fatty acids (2610 mg) are also beneficial. According to University of Michigan researchers, omega-6 fatty acids aid cell function and formation. It may also be crucial for a fetus’s and infant’s appropriate brain development [23]. Finally, research shows that the fatty acids present in canola oil may lower cholesterol levels and reduce inflammation biomarkers, making it a great addition to anti-inflammatory foods in our diet. Canola oil may also be beneficial to diabetics, since studies have shown that it helps to lower glycemic load [23].

6 Major Applications of Canola Oil Canola oil is used as an additive in many materials including biocomposites, coatings, biofuels, food, cosmetics, cleaning agents, lubricants, bitumen emulsions, glue manufacturing, and as a component in animal feed production. Because of its outstanding lubricating qualities, this oil is widely used as an additive to increase the lubricity of petroleum fuels. These characteristics are linked to the saturation and hydroxylation of canola oil components, among other features. It has been discovered that when unsaturation levels rise, so does lubricity [24–50]. Some of the major applications of canola oil as an additive being investigated and utilized by various groups have been mentioned in below: (i) Food Applications Canola oil is quite useful for the daily food applications. It’s one of the healthiest, most flexible, most cost-effective cooking oils on the market. Canola oil is suitable for everyday usage in just about every culinary application, from salad dressings, sauces, and marinades to baking, snacking, and pan release spray and deep-frying, thanks to its healthy fat profile, neutral flavor, light texture, and high heat tolerance [21, 51]. Canola oil is widely available at grocery stores in the United States and Canada [51]. Traditional canola oil performs well and has a high smoke point, making it ideal for use in high-heat cooking (Table 7). Sautéing, stir-frying, deep-frying, baking,

Canola Oil as a Bio-additive: Properties, Processing and Applications Table 7 Food oil smoke points [51]

73

Oil smoke point Sunflower high-oleic

F

°C

478

248

Canola high-oleic

475

246

Peanut

471

244

Canola

468

242

Safflower high-oleic

468

242

Corn

453

234

Sunflower

464

240

Soybean

453

234

Safflower

446

230

Grapeseed

453

224

Olive processed

428

220

Extra virgin olive

331

166

fondue, marinades, and vinaigrettes may all be done with the oil. It may also be used to make flavored oils and can be used to replace solid fat in baking recipes [51]. Increased amounts of the monounsaturated lipid oleic acid displace a tiny percentage of polyunsaturated fats found in traditional canola oil in high-oleic canola oil (Table 8). The degree of unsaturation in an oil determines its stability. Oils containing more polyunsaturated fats, such as ALA and LA, are less stable than those containing more oleic acid. As a result, high-oleic canola oil is more heat resistant and lasts longer than regular canola oil [51]. (ii) Biodiesel Production Canola oil can be also utilized as a source of Biodiesel production. The primary components of canola oil are linoleic, oleic, and linolenic acids along with the physiochemical characteristics determine whether or not canola oil may be utilized as a diesel engine fuel [50]. Intensive research is currently being conducted on the utilization of canola oil as a fuel for diesel engines as well as a supplement to petroleum fuels [52–58]. In a review article, Ge et al. [58], discussed among other things, that canola oil might be used as a good alternative fuel in diesel engines without engine modification. Górski et al. [53] have revealed that canola oil may be employed in common rail diesel engines without requiring engine modifications. Other researchers [53–57] believe that with the addition of specific additives, canola oil may be utilized as a diesel engine fuel. On the one hand, using oil as a biofuel may be advantageous, but its environmental impact (closed CO2 cycle in the atmosphere) must be considered. Further, this might be connected to a boost in the agricultural economy. Since then, viscosity, density, and surface tension have been the most significant characteristics defining the practical usage of canola oil. Furthermore, the wetness of various components of the engine during operation with biofuels cannot

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Table 8 Dietary fat comparison chart [51] Oil

Saturated Fat

Monosaturated Fat

Polyunsaturated Omega-3 Fat

Polyunsaturated Omega-6 Fat

Canola

7

61

11

21

Canola high-oleic

7

70

3

20

Safflower

8

77

1

14

Flaxseed

9

16

57

18

Sunflower

12

16

1

71

Canola

13

29

1

57

Olive

15

75

1

9

Soybean

15

23

8

54

Peanut

19

48

Trace

33 54

Cottonseed

27

19

Trace

Lard

43

47

1

Palm

51

39

Trace

Butter

68

28

1

3

Coconut

91

7

0

2

9 10

be overlooked [50]. Recently, Zdziennicka et al. [50] reported a useful work that estimates the surface tension and contact angle of unsaturated fatty acids on polytetrafluoroethylene (PTFE), poly (methyl methacrylate) (PMMA), and engine valve surfaces. (iii) Epoxy Resins A range of compounds, including epoxy resins, can be made from vegetable oils or their derivatives [59]. Epoxy resins are appealing because they don’t need volatile reactive diluents like styrene to dilute them, whose emissions are regulated by the Environmental Protection Agency [59]. An epoxide is a cyclic ether in which the oxygen atom is part of a ring of three atoms. Epoxide units make up an epoxy resin. Epoxidation is a simple process for making epoxy resins from of unsaturated vegetable oils [59]. Epoxidation is the process of adding one oxygen atom to each unsaturation (C=C) in a fatty acid chain, generally in the presence of a phase transfer catalyst and a percarboxylic acid or hydrogen peroxide (as shown Fig. 6 [60, 61, 59]). Epoxy resin quality is determined by the epoxidation process [62, 63] and the fatty acid composition of the vegetable oil [64, 61, 59]. Perez et al. [59] published a study in 2007 that sought to produce and described the canola epoxides and canola methyl ester epoxides, as well as their performance in a fiberglass composite application. A percarboxylic acid (m-chloroperoxybenzoic acid) and hydrogen peroxide (50%) were employed in this work for epoxidation [59]. In comparison to a commercially available soy-based resin, the canola-based resin had reduced iodine contents, oxirane oxygen concentration, and viscosity. When

Canola Oil as a Bio-additive: Properties, Processing and Applications

75

Fig. 6 Conversion of C=C to epoxy with a percarboxylic acids and b hydrogen peroxide [60, 61, 59]

compared to a 100% synthetic epoxy, both types of resins in mixes with synthetic epoxy reduced the flexural modulus and flexural strength of composite samples [59]. Later, the same group used canola oil with a typical oleic acid concentration (64%) and soybean oil with a low oleic acid content (22%) that were epoxidized insitu using peracetic acid and a heterogeneous catalyst [65]. Bio-based epoxy resins were combined with a synthetic epoxy resin and an anhydride curing agent for use as the matrix in composites with E-glass as the structural fiber in their study. In addition, a control was made using a 100 percent synthetic epoxy resin. The findings revealed that the degree of unsaturation and the quantity of bio-based epoxy resin in the matrix had a direct impact on the composites’ mechanical properties. According to this study, using bio-based epoxy resins in the manufacturing of composite materials reduces reliance on petroleum-based resins and might potentially result in a valuable vegetable oil-based composite [65]. Similarly, Kong et al. [66] conducted a study based on bio-based resins produced from vegetable oils that can offer a more environmentally friendly alternative to petroleum-based thermoset resins. According to this study, resin systems developed from epoxidized canola oil and polyurethanes made from polyols derived from canola oil show promise as cost-effective materials with a high renewable content. Figure 7 depicts biocomposites fabricated by using epoxidized canola oil (ECO) with various lignocellulosic particles and fibers [66]. (iv) Meat Emulsion Canola oil is one of the oleic acid-rich vegetable oils that have both health benefits and potential applications in meat products. When used in an emulsion-type chicken sausage, canola oil inhibits the development of diastolic dysfunction in a diet-induced rat model of obesity and has good technical properties [67–69]. Another prospective substitute for solid animal fat is the edible oil extracted from the seeds of Perilla fructescens (Perilla), which is commonly used in Asia for culinary purposes. Perilla oil contains around 54–64% alpha linolenic acid and fatty acid (n-3) that has been shown to have health advantages in humans. Supplementation with ALA from perilla oil decreases plasma total and LDL cholesterol concentrations in non-diabetic, borderline-to-moderate hypercholesterolaemic human subjects [70, 71].

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Fig. 7 A view of the biocomposites of wood chips (cedar), flax fiber, hemp fiber and straw with ECO resin [66]

According to Utama et al. [69] in order optimize the benefits of these oils while maintaining similar technological properties as using animal fat in meat products, an oil/water (o/w) emulsion could be formulated prior to application in the processing of meat products. The team used response surface methods to optimize the preparation of an oil/water (30:70 w/w) emulsion composed of a blend of perilla oil and canola oil (30:70 w/w) as a substitute to an emulsion form of meat product based on animal fat [69]. The results revealed that the use of 50% oil in the (o/w) emulsion could reduce the fat content of the final products. Further, the employment of inulin (IN) in the formulation of an (o/w) emulsion could fulfill the need for dietary fiber [69]. (v) Coating Materials In general, among other bio-derivatives, vegetable seed (VS) oils are regarded as one of the most significant renewable resources for the production of paints and coatings, among other uses such as biodiesel, adhesives, inks, plasticizers, cosmetics, amphiphilic copolymers, biomedical, and so on [72]. Due to their biodegradability, nontoxicity, sustainability, multifunctionality, their plenty of availability, low cost, and simplicity of processing into valuable low molecular polymers triglyceride-based VS have a wide range of applications (e.g. canola, linseed, sunflower, palm, castor, nahar, soybean, and jatropha oils) [72, 73]. Polyols, epoxies, alkyds, polyurethanes, polyestermides, and polyetheramides are used as precursors in the production of anticorrosive and antibacterial coatings [72–76]. Keeping in view of these facts, M. Alam et al., successfully synthesized canola oil-based poly (urethane-oxalate-amide)/fumed silica (FS) coating material made of nanocomposites via an in-situ method [76]. The synthesis scheme of canola oil can be seen in Fig. 8 [76]. The group selected canola oil because of its fatty acid makeup, oil contains 57 percent oleic (C18:1), 21.5 percent linoleic (C18:2), and ten percent linolenic (C18:3) unsaturated fatty acids. A two-step procedure of

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amidation and condensation was used to make hydroxyl terminated poly (oxalateamide) from canola oil. Second, fumed silica (1 to 3 weight percent) was dispersed in hydroxyl end poly (oxalate-amide), by subsequent reaction with toluene-2,4- diisocyanate (TDI) to create poly (urethane-oxalate-amide)/fumed silica nanocomposite [76]. With the addition of FS the coatings showed a significant increase in terms of physico-mechanical characteristics for instance pencil hardness, impact resistance, bend test, gloss, scratch hardness, and cross hatch, according to this study [76]. (vi) Protein Co-precipitate Protein co-precipitates are an essential food component because they increase food’s physical, functional, nutritional, chemical, biological, nutraceutical, and medicinal

Fig. 8 Synthesis scheme of Canola oil-based Poly(urethane- oxalate-amide)/FS (CAPUOA)/FS nanocomposite, R = Alkyl chain of Canola (CA) oil [76]

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characteristics [77]. Protein co-precipitates may potentially contain a beneficial influence on dietary protein allergenicity [77]. Although there are several techniques for fabricating protein co-precipitates, it may be possible to develop a novel and unique strategy for making protein co-precipitates with the largest protein yield so that they may be utilized as a commercial food product [77]. However, there is little information on how the food business uses protein co-precipitates when designing goods for different types of consumers [77]. In a notable work M. H. Alu’datt et al., evaluated the present state of protein coprecipitate investigation as a means to improve the use of protein-rich raw materials (e.g., dairy protein), oil seed meals (e.g. sesame, soybean, flaxseed, and canola), and by-products (e.g. brewing yeast) [77]. According to it, protein co-precipitates are an approach to resolving critical amino acid composition deficiencies in single-source proteins by combining proteins from several sources, resulting in components with acceptable functional characteristics and appealing sensory properties [77]. (vii) Biocomposites Currently, there is a concentrated effort around the globe to develop biocomposites, using bio polymers/materials derived from agricultural resources and natural fibers, and/or biocompatible synthetic polymers. Injection, compression, and thermoformable grade biocomposites, made from natural fibers and polypropylene, have been increasingly used in automotive industry [78, 79]. Triglycerides are the main component of plant oils such as canola oil, soybean oil, corn oil, linseed oil, and sunflower oil [9]. Triglyceride-based polymers have been used in different types of industrial products such as pressure sensitive adhesives, inks and coatings [80]. They have multiple functional sites per molecule, which enable them to copolymerize and cross-link with low molecular weight monomers like styrene. Addition of styrene decreases the viscosity of the triglycerides, which makes them suitable for inexpensive composite manufacturing processes like Vacuum Assisted Resin Transfer Molding (VARTM) [81, 82] while enhancing the mechanical properties of the cured polymer. Among plant-based oils, canola oil contains relatively lower amount of saturated fatty acids that do not polymerize, and thus, this is likely to lead an enhancement in properties. However, the unsaturation level (number of double bonds per triglyceride) in canola oils is relatively less than that in soybean or linseed oils. The overall properties of the canola oil-based resins would depend on both unsaturation and saturation levels. Additionally, the level of chemical modification of these unsaturated sites would influence the property of the canola oil based thermoset resins and their viscosity, which would in turn influence the wettability and successful impregnability of the natural fiber mats during VARTM process [9]. In 2008, Fahimian et al. [9] reported a work in which the group developed two canola oil-based resins–acrylated expoxidized canola oil (AECO), maleinized acrylated epoxidized canola oil (MAECO), and evaluated their performance as compared to those of neat resins. Hemp and flax fiber mats were also manufactured using canola oil. In these studies, biocomposites using these resins and mats were successfully manufactured using VARTM. Due to their potential to offer comparable properties

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and cost advantages, hemp and flax fibers are currently being explored as an alternative to glass fibers in polymer composites used in building products, automotive parts, etc. in Europe and North America [9]. Canola oil contains high content of oleic acid. It has been used as a plasticizer for poly(3-hydroxybutyrate) and starch films, as lubricant, in production of polyurethanes and polyhydroxyalkanoates, and biodiesel, apart from being used for edible purposes [16, 83–91]. In a notable work, M. Alam and his group [16] explored the fabrication of a poly (ester–ether–urethane) amide from Canola oil. In this work, the group selected canola oil as a raw material, transformed into diol fatty amide, to prepare canola oil-based poly (ester–ether–amide–urethane) nanocomposite coatings by lactic acid for esterification, fumed silica (FS) as nanofiller, and toluene–2,4-diisocyanate [TDI] as curing agent. According to its findings, the coatings revealed good physico-mechanical and corrosion resistance against a 3.5 wt% NaCl solution (as shown in Fig. 9). This unique technique paved path for utilization of vegetable oils by simple, single-pot derivatization method, to be applied as organic coatings and nanocomposite coatings. In a latest investigation reported in 2021 by Najmah et al. [92], an insulating composite was fabricated from the sustainable building blocks e.g., wool, sulfur, and canola oil. The researcher made their key material by the hot-pressing the raw wool

Fig. 9 EIS spectrum of CPEEUA/FS conducted in 3.5 wt% NaCl solution (corrosive medium) as a function of exposure times [16]

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with a polymer made from sulfur and canola oil (a renewable feedstock). According to their findings, the powdered polymer easily holds static charge, which facilitates its binding and coating of the wool fibers and the formation of the composite mat after hot pressing. Moreover, the wool filler imparted tensile strength to the composite, with tensile modulus improved 10-fold for some samples. It further revealed that wool facilitated excellent flame resistance to the composite, and hence, the composite became an effective thermal insulator.

7 Conclusion Upon considering the demand on vegetables and plants based edible oil which have obtained much attention because of their high MUFA and PUFA composition. Consequently, the current chapter demonstrated a comprehensive review which appraises some insight into the field of vegetables seed oil production, especially on the canola oil or rapeseed oil. Canola oil is the 3rd most widely produced vegetable oil in the world, behind palm oil and soybean oil, as already mentioned in Table 2. Canola oil is mostly produced in countries like China, the EU-27, Canada, India, and Japan. Due to its health benefits and nutritional properties, canola oil is treated as the healthiest edible oil available. Canola oil consist of both omega-3 and omega-6 fatty acids, that makes it the healthiest cooking oil. Canola oil is also high in vitamins E and K, both of which are beneficial to the skin. We have discussed here about various physical, chemical and functional properties, its refining process and advantageous features. It also discusses canola oil nutritional properties, health benefits and concerns in details. Canola oil has remarkable features like having fatty acid contents and amount of phytosterols, polyphenols and tocopherols. It contains around 12% a-linolenic acid (omega-3) and approximately 65% oleic acids. Furthermore, as compared to other popular vegetable oils, canola oil contains a low quantity of saturated fatty acids (7%). Canola oil contains a wide variety of its uses including for biofuels production, its useful role in cosmetics, cleaning agents, lubricants, bitumen emulsions and glue manufacturing. In the last section of the chapter, we have discussed some of the major applications including food applications, biodiesel production, composites, epoxy resins, meat emulsions, and polymeric coatings, and the new developments which are being explored by various groups of researchers. The data on production and consumption, and health benefits helps in identifying how much of the canola oil should be used for industrial applications other than those needed for food, keeping in mind sustainability concepts. Physico-chemical and functional properties, and information on refining of canola oil help us to use this oil effectively as an additive in various industrially important materials. Thus, we strongly believe that this book chapter will be very helpful for the investigators working in the area of vegetables and plants based edible oils in selecting and using canola oil effectively and in a sustainable manner for various domestic and industrial applications including in biocomposites.

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Figure/Table No

From publishers/authors

Figure 1 [Ref. No. 1]

Elsevier Science Ltd. The Netherlands

Figure 2 [Ref. No. 3]

John Wiley & Sons, Ltd. Ltd, UK

Figure 3 [Ref. No. 4]

From the online Link: https://www.statista.com/

Figure 4 [Ref. No. 7]

www.shutterstock.com/ko/search/canola+oil

Figure 5 [Ref. No. 22]

From the online Link: https://www.canolainfo.org/health/canola-oilis-healthy.php

Figure 6 [Ref. No. 59]

The American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Figure 7 [Ref. No. 66]

WILEY–VCH Verlag GmbH & Co. KGaA, Weinheim

Figure 8 [Ref. No. 76]

MDPI Publisher, Basel, Switzerland

Figure 9 [Ref. No. 16]

MDPI Publisher, Basel, Switzerland

Table 1 [Ref. No. 1]

Elsevier Science Ltd. The Netherlands

Table 2 [Ref. No. 6]

Elsevier Science Ltd. The Netherlands

Table 3 [Ref. No. 6]

Elsevier Science Ltd. The Netherlands

Table 4 [Ref. No. 41]

John Wiley & Sons, Ltd. Ltd, UK

Table 5 [Ref. No. 10]

Elsevier Science Ltd. The Netherlands

Table 6 [Ref. No. 10]

https://www.canolainfo.org/health/canola-oil-is-healthy.php

Table 7 [Ref. No. 51]

https://www.canolainfo.org/health/canola-oil-is-healthy.php

Table 8 [Ref. No. 51]

https://www.canolainfo.org/health/canola-oil-is-healthy.php

Acknowledgements Authors are thankful to the publishers/authors for granting the permission for the reproduction of the following figures and the table taken from Elsevier Science Ltd., The Netherlands, John Wiley & Sons, USA & U.K, from the online weblinks, The American Society of Agricultural and Biological Engineers, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, and MDPI Publisher, Switzerland. The details of those figures and tables with their respective sources are given in the above Table.

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Vegetable Oil Based Polyurethane Composites Saima Khan Afridi, Khalid Umar, Tabassum Parveen, M. Hazwan Hussin, and Mohd Jameel

Abstract In Over the past two decades, bio derived products have replaced petroleum-based polymeric materials at an exponential rate. The benefit of this replacement is decreased environmental degradation, fuel consumption, and fuel cost. One such greener route suggested for this, is the utilization of vegetable oils as feedstock to synthesize polymeric products, such as polyurethanes (PUs). Vegetable oils are cheap and abundant in quantity worldwide. Vegetable oils can be converted into diols, polyols, and isocyanates by implementing a variety of procedures. There is a wide variety of versatile polyurethane polymers based on these vegetable oil-based monomers. The thermal, mechanical, and physical, properties of these PU-based biocomposites is comparable and often better than those of conventional petrochemical polymeric composites. Moreover, a variety of biocomposites can be prepared by choosing a wise combination of vegetable oils, polymerization route and types of fibres/fillers as reinforcement material. These biocomposites find numerous applications in adhesives, several types of coatings, sensors, biomedical field, automotive, plasticizers and much more. Keywords Vegetable oil · Polyurethane · Biocomposites · Polymers · Biomedical application

Acronyms VO PU

Vegetable Oil Polyurethane

S. K. Afridi · K. Umar (B) · M. H. Hussin School of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia e-mail: [email protected] T. Parveen Department of Botany, Aligarh Muslim University, Aligarh, India M. Jameel Department of Zoology, Aligarh Muslim University, Uttar Pradesh, Aligarh 202002, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 S. A. Bhawani et al. (eds.), Vegetable Oil-Based Composites, Composites Science and Technology, https://doi.org/10.1007/978-981-99-9959-0_5

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EVO NEVO pMDI HDI GO TGA Tg ESO MWCNTs TDI MDI TMDI HDI

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Edible vegetable oils Non-edible vegetable oils Polymeric diphenyl methane di-isocyanate Hexamethylene diisocyanate Graphene oxide Thermogravimetric analysis Glass transition temperature Epoxidized Soyabean Oil Multiwall carbon nanotubes Toluene diisocyanate Methylene diphenyl diisocyanate 2,2,4-Trimethylene hexamethylene diisocyanate 1,6-Hexamethyl diisocyanate

1 Introduction Our everyday lives are enriched using plastic, which we use for shelter, clothing, communication, and transportation, alongside the everyday conveniences of modern living. Over 380 million tonnes of plastic were produced in 2015, up from fewer than 2 million tonnes in 1950 [1]. There are several reasons for the rapid growth in the consumption of plastics: (a) the low density of plastics; (b) excellent safety and hygiene characteristics of plastic packaging; (c) adaptability and versatility; (d) outstanding electrical and thermal insulation properties; and (e) barely any painting or polishing is required [2]. Earlier, polymers were typically made from petroleum sources, and around 7% of all the petroleum and gas in the world was used in their manufacture [3]. Moreover, there is a substantial challenge to sustainable development because of environmental concerns related to non-degradable synthetic polymers. As a result of ongoing oil price spikes and concerns about oil supplies, biorenewables are being investigated for plastic manufacturing stocks. There are many biorenewable materials that have been identified as potential feedstocks, but vegetable oils stand out as the most promising. Furthermore, Anastas and Warner outline the use of renewable raw materials as one of their 12 principles of green chemistry [4]. There is a rich supply of polymer precursors in vegetable oils (VOs) that can be modified to exhibit a variety of functional and structural properties, causing the development of new materials. Modern polymers have assumed a pivotal role as materials for almost every aspect of manufacturing such as infrastructure, medical equipment, consumer goods, automobiles, and many others. The reasons polymers are an advantageous material over other materials are their easy processing, excellent strength/density ratios, tailorable properties, physical and chemical resistance, and affordability [5] One such class of advanced polymers are polyurethanes (PUs). In 1937, Otto Bayer and colleagues invented the Polyurethane (PU) polymer group [6]. Due to the presence

Vegetable Oil Based Polyurethane Composites Table 1 Typical oil content of plant seeds [5]

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Plant

Oil (wt%)

Potato

0.1

Lentils

1

Soyabean

20

Tung

30–40

Coconut

34

Peanut

44

Linseed

45–50

Sunflower

47–50

Castor

50

Walnut

64

Pecan nut

71

of urethane groups in their chemical structure, polyurethanes possess outstanding abrasion resilience, adhesiveness, chemical stability, and thermal stability [7]. There is oil available in almost every plant, with quantities ranging from traces to up to 70% or more. The seeds of plants contain the most oil. Table 1 illustrates the oil content in various edible and non-edible plant seeds [5]. The use of VO is not just in cooking and household, rather it is interesting to note that VO are also used in coatings, lubricants, paints, and plasticizers [8]. This has attracted the academia and industries to focus on its studies and production respectively. The smart choice to replace petroleum materials with VO is their abundant quantities, cheaper price and sustainability [9]. The composition of plant oils consist of triglycerides, these are the esters of glycerol and three fatty acids (Fig. 1). The double bond conjugation in the VOs serves as the reactive site for superior polymerization activity. But it’s uncommon in most VOs except for tung oil. However, in other VOs, the major reactive sites are esters, epoxy (oxirane) groups or hydroxyl groups [9, 10]. The number of carbon atoms in fatty acid chains can range from 8 to 24, and there are between 5 and 7 double bonds between them [5, 8]. According to Table 2, the most common fatty acids in vegetable oils have the following chemical formulas: The fatty acids composition plays a major role in distinguishing different vegetable oils. It is noteworthy that almost all vegetable oils contain a good amount of regular fatty acids. Firstly, saturated fatty acids include palmitic (C16:0) and stearic (C18:0) and secondly unsaturated fatty acids include oleic (C18:1), linoleic (C18:2) and linolenic (C18:3). (In this case, the first number indicates how many carbon atoms are in the chain of the fatty acid, while the second number shows how many carbon– carbon double bonds there are in the fatty acid) [8, 9]. Now, the modification in the triglyceride structure of VO, through various routes leads to the formation of various functionalized molecules that lead to different types of PU [11]. Table 3 illustrates the fatty acid composition of vegetable oils, the quantity of carbons and double bonds per triglyceride, annual world production, iodine value, and largest producer country.

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Fig. 1 In the triglyceride structure, the fatty acids side chains are on R1, R2, and R3

Table 2 Chemical formula of some common fatty acids

Fatty acid

Formula

Linoleic

C18 H32 O2

Ricinoleic

C18 H34 O3

Caprylic

C8 H16 O2

Palmitic

C16 H32 O2

Linolenic

C18 H30 O2

Stearic

C18 H36 O2

Oleic

C18 H34 O2

α-eleostearic

C18 H30 O2

Vernolic

C18 H32 O3

In fact, values of iodine are typically expressed in units of centigrams of iodine per gram of sample and are determined by the amount of iodine absorbed per gram of sample. Higher levels of iodine indicate higher levels of unsaturation [12]. Moreover, there are two classes of vegetable oils (1) Edible vegetable oils (EVO) (2) Non-edible vegetable oils (NEVO). Although both categories can be utilized for polymerization purposes but, a major benefit of utilizing NEVO is its non-food nature and no effect on the food supplies worldwide [7]. Furthermore, through polyaddition reactions, different vegetable oil-based polyols (containing hydroxyl groups) react with di- or Poly isocyanates to produce polyurethanes (Fig. 2). Chemistry and the combination of polyols and isocyanates determine the properties of polyurethanes [7, 13]. There were 18 million tonnes of polyurethanes consumed worldwide in 2016 [14]. There are relatively few isocyanates used by industry, and a variety of polyols are used to produce polyurethane products of a wide range of properties [8]. There exist various methods for polyol production from both EVO and NEVO, that eventually lead to PU formation. These include esterification, hydroformylation,

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Table 3 Degree of unsaturation, composition of vegetable oils, iodine value, annual production and largest producing country [5, 8] Oil

Iodine World Largest Production Producing Double C16:0 C18:0 C18:1 C18:2 C18:3 value (mg/ (MMT)b Countryc Bondsa 100 mg)

Sunflower

4.7

7.0

4.5

18.7

67.5

0.8

125–140 22.05

Ukraine

Soyabean

Composition of fatty acid (%)

4.6

10.6

4.0

23.3

53.7

7.6

123–139 61.64

China

Cottonseed 3.9

21.6

2.6

18.6

54.4

0.7

98–118

China

Rapeseed

3.8

3.8

1.2

18.5

14.5

11.0

100–115 27.48

Canada

Peanut

3.4

11.1

2.4

46.7

32.0

–

84–100

6.47

China

Olive

2.8

9.0

2.7

80.3

6.3

0.7

76–88

3.28

Spain

Palm

1.7

44.4

4.1

39.3

10.0

0.4

50–55

76.54

Indonesia

Coconut

–

9.8

3.0

6.9

2.2

–

7.5–10.5

3.51

Indonesia

5.21

a Number of C-C double bonds per triglyceride. b Annual world production in Million Metric Tonnes. c Data

from Foreign Agricultural Service/USDA 2021

amidation, ozonolysis, epoxidation, reduction etc., and utilizing functional groups in their structures. This chapter discusses each conversion route in detail. A detailed discussion on a variety of VO-based PU composites is also presented. Furthermore, various applications of the PUs in anticorrosive, antibacterial, coatings, and adhesives will also be discussed. A discussion is also given about diisocyanates and polyols, which form the basis of PUs.

2 Vegetable Oil-Based Monomers 2.1 Vegetable Oil-Based Polyols The hydroxyl groups needed to produce polyurethanes are not naturally present in most vegetable oils, except for castor oil. A triglyceride, however, can introduce such groups because it contains double bonds and ester functionality. Most of the polyols present in vegetable oil incorporate hydroxyl groups by utilizing the double bond between carbon double bonds in vegetable oils. The vegetable oil must contain at least 2.5 double bonds per triglyceride to produce polyurethane with sufficient properties. The level of unsaturation in palm oil is very low, that is only 1.7 double bonds per triglyceride, despite the fact that it is the most abundant vegetable oil, this precludes its use in polyurethanes. However, there is a greater amount of use for soybean oil to make polyols in large quantities because it is available on a large scale as well as because it contains 4.6 double bonds per triglyceride [8].

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2.2 Vegetable Oil-Based Isocyanates Plant oils have been used to produce poly- and diisocyanates, but little research has been done on them. Vegetable oils have intrinsically aliphatic isocyanates. These compounds can be classified into aliphatic, cyclo-aliphatic and aromatic diisocyanates. Industrially, aromatic diisocyanates are the most common, such as methylene diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI) [7]. It is important to have high reactivity for foaming when using aromatic diisocyanates instead of aliphatic diisocyanates. Because polyurethanes are typically used to make hard and pliable foams, aliphatic diisocyanates have fewer uses and are commonly employed for coatings, because the vacancy of unsaturation makes them an excellent coating material [8]. Aliphatic diisocyanates include 2,2,4-trimethylene hexamethylene diisocyanate (TMDI) and 1,6-hexamethyl diisocyanate (HDI). Petroleum resources are the most common source of diisocyanates. It has been suggested that diisocyanates are prepared by Curtius rearrangement from renewable resources [7].

3 Vegetable Oil-Based Polyurethane Polymers An incredibly diverse class of polymers, polyurethanes (PUs) range from coatings to elastomers and sealants [15, 16]. Polyisocyanates and polyols are polyadditioned to make polyurethanes. In contrast, a variety of polyols can be obtained, and only a few polyisocyanates are commercially available. A polyol’s properties thus depend on the choice of polyol [17]. In order to tailor polymer structures to meet specific application requirements, reacting components must be selected at appropriate ratios. Polyols are produced as soft amorphous segments by using plant oils with aliphatic chains. This provides flexibility to PUs. Cyclic isocyanates, however, provide mechanical strength and act as hard segments. A segmented domain structure makes it possible for the PUs to have a good balance of properties and performance, such as flexibility, mechanical strength, toughness, and durability [18]. Castor oil is the only common vegetable oil that contains naturally occurring hydroxyl groups, which allows it to be most useful to produce PUs. Triglycerides, however, provide an appropriate platform for introducing OH groups, due to the reactive sites present in them [16].

3.1 PUs from Castor Oil The three principal producers countries of castor oil are India, Brazil and China. Its non-food grade status makes castor oil an extremely versatile feedstock for industrialscale applications. Castor oil has approximately 2.7 hydroxyl groups per triglyceride, which makes it suitable for PU production without any modification [19]. Throughout castor oil’s molecules, hydroxyl groups are evenly distributed. The result

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is a polyurethane with a uniform cross-linked structure, which is typically characterized by good mechanical and thermal properties [8]. Depending on the isocyanates, chain extenders, and stoichiometry, PUs with tunable properties can be prepared. These properties include thermomechanical characteristics, thermal stability at high temperatures, and electrical conductivity [20, 21]. Castor oil has naturally occurring hydroxyl groups, which have been used in making polyurethane foams, elastomers, and rigid foams [8]. By transesterification of castor oil by glycerol and using castor oil with fibroblast cells, PUs can be prepared in various forms [22, 23]. Polyols made from recycled materials have also been used to react with castor oil [24].

3.2 PUs from Epoxidation/Oxirane Ring Opening A nucleophilic reagent such as water, alcohol, amines, or halogen acids is used to open the oxirane ring after epoxidation of vegetable oils, which converts them to polyols [25]. The process of epoxidizing vegetable oils involves creating peracids in situ by reacting hydrogen peroxide with acetic or formic acids [26] Most commercial processes use this method as it produces sufficient yields of epoxidized oil (75– 90%). To open the epoxide ring, we can use a variety of nucleophilic reagents which includes the universal solvent, “water” as well [27]. Catalyzing the process can also be accomplished using inorganic acids like fluoroboric acid, sulphuric acid, phosphoric acid, and Lewis’s acids [28, 29]. Polyols produced from alcohols have the best properties because they are liquids while still possessing high function. The commonly used alcohols include methanol, ethylene glycol, propylene glycol [30]. When using epoxy groups, using diols is a wise choice because they contain two hydroxyl groups per epoxy group. Primary hydroxyl groups produced in PU production by using propylene glycol are three degrees more reactive than secondary hydroxyl groups. Moreover, primary hydroxyl groups can be formed from ethoxylation of secondary hydroxyl groups [31]. Polyols are commonly produced using soybean oil as the vegetable oil of choice. Soybean oil-based polyol can be converted into polyurethane foam, coatings, elastomers, and adhesives by reacting with different isocyanates [32]. Polyurethanes made from epoxidized vegetable oils are influenced by numerous factors, including the type of oil and the fatty acid composition, epoxidation degree, location and number of hydroxyl groups and residual carbon–carbon double bonds in the final polyurethane, and presence of long dangling chains [33]. Therefore, different types of oil such as mid oleic sunflower, canola, sunflower, corn, and linseed oils, have been used [34]. Researchers have observed that the properties of polyurethanes obtained are mainly determined by the density of crosslinks and not so much by the location of the susceptible sites in fatty acids. The densities, viscosities, and viscous-flow activation energies of the polyols from ESO reacted with halogen acids, methanol and hydrogen decrease in the following order: hydrobromic acid > hydrochloric acid > methanol > hydrogen [35]. As with glass transition temperature, robustness of PU

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follows the same pattern. Aromatic triisocyanate gives PUs with higher strengths and glass transition temperatures while use of aliphatic diisocyanate produces PUs with greater elongations at break and higher swelling [32]. Another interesting point is that PUs that are made of polyols with high molecular weights present greater thermal resistance, in comparison to those from oil of castor and methoxylated-soybean oil polyol [17]. Finally, another route of epoxidation is through catalysis [36].

3.3 PUs from Transesterification/Amidation It is also possible to prepare vegetable oil-based polyols through transesterification with alcohols or amidation with amines with enzymatic or basic catalysts [37]. The most recurrently used polyol is glycerol. Using an excess of glycerol in the transesterification of vegetable oils produces monoglycerides in a single step, thus providing economic benefits [38]. Since there are β-hydrogens on adjacent carbon atoms in glycerol, water readily evaporates from it at high temperatures, creating undesirable unsaturated compounds [8]. Several polyols with no b-hydrogens have been used to replace glycerol in transesterification, including trimethylolpropane and pentaerythritol [39]. Except for castor oil, which contains hydroxyl groups, fatty acid chains in most products lack hydroxyl groups. Because the chains of fatty acid lack hydroxyl groups, they act like plasticizers. However, castor oil contains naturally occurring hydroxyl groups in its ricinoleic fatty acid chains. Catalysing the transesterification reaction usually involves bases, however, enzymes can also be used. Enzymatic catalysis is beneficial and eco-friendly technique but unfortunately, the excessive-high cost associated with this catalytic technique makes its commercial usage inevitable. For the process of amidation of vegetable oils, another good choice is amines, similar to the process of transesterification. Vegetable oils are transformed into polyols by transesterification or amidation, producing polyurethanes that are very versatile. Materials with the desired properties for coating applications may be formulated using transesterification/amidation agents, polyols, and isocyanates [5].

3.4 PUs from Hydroformylation/Reduction Hydroxymethyl groups are added to fatty acid double bonds during the two-step hydroformylation/reduction process. Using the syngas method in combination with a catalyst, vegetable oil is first transformed into aldehydes, which are then reduced with H2 to yield hydroxyl groups in the next step [8]. A Rhodium catalyst is highly potent, achieving a high conversion rate (95%) but is quite pricey and requires the use of Raney nickel during reduction. Therefore, hydroformylation and reduction are catalysed by cobalt complexes, which are significantly cheaper. However, cobalt

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complexes have the disadvantage of having a lower yield of hydroxylated products (65%) due to double bond isomerization [40]. Moreover, because of the hydroformylation/reduction process, primary hydroxyl groups are formed that demonstrate greater reactivity towards isocyanates rather than any secondary hydroxyl groups that could be produced by other methods. Nevertheless, the catalyst (especially rhodium) needs to be fully recovered to make commercial sense [8]. When polyols are prepared by hydroformylation/reduction processes, there is a greater likelihood that polyurethane will form and a small amount of catalyst will be required when forming rigid foam, in comparison to polyols formed by methanolysis of soybean oil [40]. Upon hydroformylation/reduction and partial esterification with formic acid, the hydroxyl groups of polyols tend to create a range of polyols with varying hydroxyl numbers [41]. In one previous literature, the rhodium catalyst Rh(CO)2 was used by Petrovic et al. to hydroformylate crude algal oil-based polyols that showed improved thermal and mechanical properties [42]. The hydroformylation/hydrogenation of castor oil led BASF to develop another commercial polyol (Lupranol Balance 35).

3.5 PUs from Ozonolysis/reduction The polyols produced by ozonolysis/reduction have primary hydroxyl groups at their terminal ends, which are highly reactive when polyurethane is formed. It is possible to produce shorter chain alcohols by cleaving carbon double bonds within fatty acids using this method under the right conditions. The vegetable oil is first treated with ozone to form an ozonide. Upon reduction by zinc, the unstable ozonide becomes an aldehyde, the primary alcohol of which is produced by Raney nickel via reduction process. By ozonolysis, the fatty acid chains are essentially split in half. By doing this, the chains are kept from being incorporated into the polyurethane, which acts as a plasticizer and weakens the materials [8]. The hydroxyl group of polyols at the end of fatty acid chains are also responsible for rigid PU production [43]. Now, ozonolysis removes double-bonded segments from the tail ends of fatty acid chains. This process results in polyols with a molecular weight around 40% lower than those obtained from oxirane ring opening or hydroformylation/reduction involving the double bonds in vegetable oils. A polyol resulting from this reaction is typically a wax at room temperature that has low viscosity upon melting [13]. The functionality of polyols prepared from ozonolysis/reduction is dominantly affected by the percentage of saturated fatty acid in VO. A comparison between the Soyabean oil and Canola oils indicates that, Canola oil has a smaller degree of carbon–carbon double bonds (3.9), and a lesser percentage of saturated fatty acids (6%) and thus has a higher degree of functionality (2.8 hydroxyl groups). It is for this reason that canola oil is widely used in the ozonolysis/reduction process, even though soybean oil is more widely produced [44]. Omonov et al. [45] examined ozonolysis-produced polyols derived from canola oil using various protic and aprotic solvents. Rather than just using an aprotic or

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protic solvent alone, the authors suggested mixing both aprotic and protic solvents in order to produce polyols [45]. With the help of ozoneolysis/reduction of canola oil and ethyl acetate as a solvent and zinc as a better reducing agent, Kong et al. synthesized polyols with much higher triol content and hydroxyl number. As a result of these polyols, Polyurethanes have higher glass transition temperatures, greater Young’s modulus, and higher tensile and elongation at break values [46]. In another study, soybean oil and glycerine (an esterification agent) were ozonolyzed/reduced to create first-grade bio-based polyols, which were used to make rigid as well as flexible foams [47].

4 Non-Isocyanate Route for Vegetable Oil-Based Polyurethanes The use of isocyanates in the synthesis of polyurethane is a significant environmental issue and poses serious industrial hygiene problems [48]. There are serious health risks associated with exposure to isocyanates, including skin irritation and eye irritation [49]. Exposure to isocyanates repeatedly may exacerbate asthma attacks since isocyanates sensitize the body [50]. Phosgene, a hazardous precursor to isocyanates, presents additional environmental risks [51]. Therefore, scientists have investigated other routes to prepare polyurethanes. Utilizing AB-type monomers such as methyl oleate or ricinoleic acid, polyurethanes have been prepared by self-polycondensation and transurethane methods [52]. Different glass transition temperatures (Tgs) were observed for soft and hard segments of polyurethane synthesized by both processes. These two processes also resulted in polyurethanes with low molecular weights [53]. At present, most research efforts are directed at cyclic carbonate and amine reactions based on vegetable oils. With the approach, no special equipment is needed, high yields are achieved, and the reagents can be used again and again [54]. In the final product, urethane molecules contain more hydrogen bonds than the molecules of the input urethane [51]. This reaction is catalysed by polystyrene-bound quaternary ammonium salts, quaternary ammonium salts, or alkali metal halides [55]. Usually, these polyurethanes had comparable mechanical properties as conventional polyurethanes and are better at absorbing water, retaining heat, and resisting chemicals [51]. Wilkes investigated how different catalysts affected CO2 and ESO reactions. In a 70-h reaction at 110 °C, tetrabutylammonium bromide achieved the greatest yield (94%). A study reported by Javni et al. revealed that aromatic and cycloaliphatic diamine thermoplastics with non-isocyanate polyurethanes had superior mechanical properties to aliphatic diamines [56]. A soybean oil-based PU composed of triamines exhibited better mechanical and thermophysical properties than one composed of diamines, according to Tamami et al. [55]. A relatively new solvent-free/catalystfree method for producing polyurethane (PU) with a high bio-content (up to 80%)

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has been developed by Averous, using glycerol carbonate. As a result, the PU could show good elastomeric properties [57].

5 Vegetable Oil Based Polyurethane Composites 5.1 Glass Fibre Composites An evaluation of the properties of soybean oil-based PU composites prepared with E-glass fibres was carried out by Hudic et al. Polyurethanes made from soybean polyol are also more thermally, oxidatively, and hydrolytically stable than analogous polyol composites made from petrochemicals. As a result, petrochemical urethane resins may be replaced by them [58].

5.2 Synthetic Fibres/Fillers Reinforcements The lightweight and versatility of synthetic fibres, like glass and carbon fibre, makes them great fibre reinforcements in composite manufacturing [59]. Husic et al. [58] produced PU composite reinforced with E-glass fibres derived from soybean oil. Vegetable oil-based composites, however, displayed better thermal stability than petrochemical composites and similar mechanical properties to those of petrochemical composites. Moreover, Bassyouni et al. developed a polyurethane (PU) composite containing castor oil, pMDI, and milled waste-light bulbs as filler. As a result of adding glass, the composite’s thermal degradation was delayed, swelling decreased, and the composites’ hardness increased [60]. The nonwoven fabric was made from PU and polyester, and the epoxy-polyurethane network contained titanate whiskers, both of which were made with castor oil, have been reported to have improved damping properties and water resistance [61, 62].

5.3 Natural Fibre/Filler Reinforcement Composites made from vegetable oils that are reinforced with synthetic fibres are used in numerous industries, including aerospace and automotive. However, they are non-biodegradable, rely on non-renewable resources, and emit carbon dioxide during manufacturing [63, 64]. Natural fibres/lignocellulosic fibres such as banana, jute [65], cellulose [66], pine wood fibres [67], wood flour [68], palm fibre [69], and sisal fibre [70] have been incorporated into vegetable oil-based polyurethane to produce green composites. (To produce green composites, natural fibres, lignocellulosic fibres, and dust such as banana, jute, cellulose, pinewood fibre, wood flour, palm fibre,

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palm oil, and sisal fiber were incorporated into vegetable oil-based polyurethanes.) The low density, low cost, recyclable, and biodegradable characteristics of these reinforcements have attracted much attention [71]. Merlini et al. used polyurethanes derived from Castor oil as matrices to process banana fibres into random short fibre mats by hand [72]. Variations in fibre volume fraction and fibre length were investigated to find out their effects on tensile modulus and strength. The highest modulus and strength for both types of composites resulted from fibre lengths of 30 mm and volume fractions of 15 vol.%. Polyurethane composites made with castor oil, reported by Miao et al. [73] increased by a factor of five in tensile strength by MDI-modified cellulose. Biocomposites can also be produced with silk in castor oil-based polyurethane. An increase in tensile strength of two times is achieved with the addition of 10% silk fibre. Additionally, silk fibres produce composites with a higher glass transition temperature [74]. A polyurethane reinforced with alpha stem cellulose fibers was also synthesized by Maafi et al. from castor oil and HDI. With up to 20% of the fibre content in the composites, mechanical properties and glass transition temperatures increased consistently, which also suggested a good dispersion [66].

5.4 Nanocomposites 5.4.1

Clay Nanocomposites

As a naturally occurring nanofiller, nano-clays are increasingly used as reinforcement in advanced materials. Chemically modified clay is typically required to ensure the effective dispersion of clay in polymer matrixes and to enhance polymer–clay interface strength. The nanocomposites obtained are stronger, have a higher tensile modulus, are more thermostable, and are able to conduct water vapor more readily [5, 75]. Using 1,4-butanediol as a chain extender and MDI l as crosslinker, Kaushik et al. prepared a castor oil-based polyurethane-nanoclay composite [76]. An increase in clay proportion increases Young’s modulus, tensile strength, and elongation at break. Nanoclays also improved the barrier property against vapor and liquid water diffusion as a result of their incorporation. Clay’s contribution to increased glass transition temperatures, tensile strength and Young’s modulus has been reported in several previous literatures, mentioned as follows. PU-organoclay nanocomposite based on castor oil was created by Gurunathan [77]. With the help of in situ fabrication, Xie prepared high attapulgite content (12 wt%) PU nanocomposites with soybean oil [78]. PU nanocomposites containing 0–5% MMT clay (quaternary ammonium modified) were developed by Mohammed et al. [79]. Cheng used silane-modified palygorskite for reinforcement of PU based on soybean oil [80]. The reinforcement of foam can also be done by using clay. Using nanoclay, Zhu et al. reinforced PU foam made from soybean oil. Nanoclays narrowed the distribution

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of cell size, decreased the average cell size, and increased the compressive strength of rigid foams [81].

5.4.2

Metallic and Silica Composites

The use of metal oxides in combination with polymers based on vegetable oil is also used to create functional nanocomposites. Polyurethane composites have also been prepared with silica reinforcements. These composites exhibit excellent thermal stability, which could make them useful in thermally protected coatings [82]. Another thermally and mechanically stable castor oil-based PU-silica nanocomposite was designed by Larock using a sol–gel process [83]. Castor oil has been thoroughly dispersed with metallic aluminium powder to form a polyurethane with superior electrical conductivity for use as conducting coatings and adhesives [84]. Ristic et al. utilized titanium (IV) oxide nanoparticles to create castor oil-based PU hybrids. As a result, Tg was reduced and composite properties such as mechanical resistance and damping were improved [85].

5.4.3

Carbon Nanotube and Graphene

A variety of other reinforcement materials can be used in advanced polymer composites, including vegetable oil-based composites, for instance graphite, graphene [86], and their derivatives [87, 88]. Polyurethane nanocomposites based on soybean oil with 1% functionalized graphene were developed by researchers instead of pure graphene. As a result of adding functionalized graphene to the PUs, they exhibited improved mechanical properties as well as improved thermal stability [89]. Using castor oil as the base material, polyurethane nanocomposites reinforced with 1% multiwall carbon nanotubes (MWCNTs) were synthesized by Ali et al. [90]. According to the authors, the modulus and tensile strength of well-dispersed MWCNTs were increased by 128% and 5%, respectively, when well-dispersed MWCNTs were used as fillers at 0.3 wt.%. Cheng et al. found that the larger-diameter MWCNTs were more easily dispersed in the soybean oil-based PU matrix than the smaller-diameter which resulted in higher tensile strength, Young’s modulus, elongation at break, and thermal conductivity of PU [91]. Other MWCNT based PUs from vegetable oils are reported in literature [92–94], which demonstrated superior mechanical, thermal and shape properties [95, 96].

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6 Anticorrosive and Anti-Bacterial Applications of VO Based PU Composites Corrosion is caused by a chemical/electrochemical reaction between metal and its environment, which results in the decomposition of the metal. Various industrial sectors are adversely affected by corrosion and microbial growth on metal surfaces, which causes enormous economic losses each year. Another aspect of microbial growth that leads to significant economic losses is the biofouling of marine coatings [97]. Anticorrosive and antibacterial properties are thus ensured by preventing the penetration of corrosive and bacterial media. Due to the presence of oxygen and nitrogen in urethane linkages, PU coats are uniform and well-adherent over the metal substrate and are therefore excellent anticorrosive coatings [98]. A major advantage of nanocomposites is that they offer corrosion protection, which is an emerging material class used for coating developments [99–101]. The incorporation of nanoparticles in NEVO-based polyurethane has been shown to improve anticorrosion properties [101, 102]. Carbon nanofillers such as graphene oxide (GO) are good examples for anticorrosive surface coatings [42]. Additionally, antibacterial coatings have enabled a means of limiting bacterial infections in a variety of settings such as healthcare equipment [103, 104]. In Yeganeh et al.’s study, benzyl triethanol ammonium chloride and castor oil were used as reactive polyols to produce antibacterial PU coatings. A satisfactory level of antibacterial activity was demonstrated by the PU samples against E. coli and S. aureus bacteria, while good compatibility was observed with mouse fibroblast L929 cells [21]. Another antibacterial nanocomposite is developed by Sharmin et al. using PU matrices based on linseed oil with copper acetate fillers [105]. Das et al. prepared polymer composites from sunflower oil-modified, hyper-branched PU with Fe3 O4 nanoparticles as antibacterial biomaterials for biomedical devices and implants [106]. In the same way, the growing COVID-19 outbreak has contributed to the high demand for antiviral coatings on personal protective equipment [7].

7 Conclusion The use of petrochemical materials for designing polyurethane composites has caused severe environmental challenges, such as consumption of fast-paced exhausting fuel reserves and higher fuel cost associated with it. A number of PU materials made from vegetable oil have demonstrated comparable properties to conventional petrochemical polymers, with some showing better performance. These materials have already demonstrated some commercial viability. This provides a greener and economic method for PU production. The chapter discussed the various synthesis routes for VO based polyols and isocyanates that lead to PU formation. Also, we discussed the reinforcement materials for enhancing the PU properties and different applications of such PUs anticorrosive and antibacterial coatings.

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Acknowledgements This article was financially supported by Universiti Sains Malaysia, (Malaysia) under short term grant; 304/PKIMIA/6315580.

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Vegetable Oil Based Epoxy Composites Akash Pratim Bora, Pragati Agrawal, and Sumit H. Dhawane

Abstract In the current era naturally occurring resources are exploited and its consumption is increasing continuously with increase in population, urbanisation and industrialization. Thus, there is a need to explore more sustainable products and techniques to overcome the demerits of conventional products. Modified vegetable oils (VOs) such as epoxidized vegetable oil (EVO) termed as biocomposite could be one of the product that have significant industrial application as plasticiser and synthetic intermediate in polyester synthesis. Still, the usage of EVO as monomer is limited in the production of high grade epoxy thermoset polymers due to its reactivity and physical properties. VOs has emerged as a promising alternative for the production of bio-based polymeric composites. Recent observations have shown its potential as a viable candidate in this field. Typically, direct polymerization and curing using various agents like acids, amines, anhydrides, etc., are used for the synthesis of epoxy biocomposites. But, the major concern in this field is the production of wholly green epoxy composites from bio-based materials with high mechanical strength. However, with the application of bio based hardener and modifications exhibited through physicochemical treatment or the addition of fillers, mechanical characteristics can be improved to a significant level. This chapter provides a comprehensive exploration of fiber-reinforced vegetable oil-based composites, covering their processing and advancements. The focus is on integrating bio-based hardeners with fibers or fillers for the synthesis of VO-derived epoxy composites.

A. P. Bora Department of Chemical Engineering, Indian Institute of Technology (Indian School of Mines), Dhanbad, India S. H. Dhawane (B) Department of Chemical Engineering, Maulana Azad National Institute of Technology, Bhopal, M.P. 462003, India e-mail: [email protected] P. Agrawal Department of Computer Science and Engineering, Maulana Azad National Institute of Technology, Bhopal, M.P. 462003, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 S. A. Bhawani et al. (eds.), Vegetable Oil-Based Composites, Composites Science and Technology, https://doi.org/10.1007/978-981-99-9959-0_6

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1 Introduction In the past few decades attempts are being made to derive new sustainable ways and effective solutions so as to re-establish the balance between economy and ecology which has been disturbed due to our exhaustive usage of pre-existing, easy to derive natural resources resulting in high C-emission, climate change and global warming. Bio composites are one of the major breakthrough in the area of green material in the field of polymer science, which can be a positive step towards re-establishing this disturbed balance. For the past few decades vegetable oil has been a centre of attraction not only academically but also industrially because of the renewable sources and materials which can be derived from them and can potentially replace the current environmentally hazardous materials (which are in use). The fibre reinforced polymers are appealing because of its biodegradability, high strength, inexpensive, light weight, recyclability, reduce fuel consumption as well as CO2 , air pollution, low density, superior life cycle and eco-friendly. One of the major disadvantages is that during its production it produces organic water pollutants and residue behind which are generally biodegradable. However, with the increase in environmental awareness, checks and regulations the use of these bio-composites have significantly increased. Globally, the production and use of these polymers are significantly increasing at a rate of 5%, thus exceeding the annual consumption over 300 million tonnes. The demand of natural fibres such as henequen, jute, banana, falx, kenaf, sisal, pineapple, oil palm, wood has increased significantly because of their usage in composite materials. The production of materials from renewable feedstocks will increase around 50% by 2050. The numerous pressures from stringent environmental regulations shifting the focus of developing environmentally tolerable thermoset resins from biodegradable materials to change the currently employing manufacturing process from fossil fuel based polymers. The thermoset polymer manufactured from the bio based raw materials, viz., vegetable oils, lipids, proteins, lignin, polysaccharides, etc., has enormous potentiality owing to their sustainability, superior properties and lower production cost [1, 2]. Due to a range of structural and compositional variations of the vegetable oils (VO), they are capable of undergoing condensation polymerisation by the addition of anhydride as a curing agent or latent catalyst [3]. Some of the VO which are drying oils like linseed, walnut and tung, etc., have been widely employed in coating industries owing to their high iodine content. They can be spontaneously cross linked to the presence of oxygen without the usage of any heat source [4, 5]. The semi drying VO which has iodine content in the range of 100–150, need heat treatment, however they are heavily consumed as food products [6]. The VOs which are non-drying and low iodine content needs sufficient heat treatment [7]. The cross-linking structures between vegetable oils and epoxy resin have greatly influenced the thermal and physical characteristics of their composite structures which impetus the required technical criterion. The VOs containing high amounts of saturated fractions in their triglycerides tends to show superior structural properties

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than that of the triglycerides containing a lesser number of saturated fractions. For instance, oils such as soybean and linseed demonstrate superior properties comparing to other VOs. There are three broadly defined categories of epoxy resins, viz., aliphatic, cycloaliphatic and aromatic. However, the most widely used one is the composite structure of diglyceride ether and bisphenol that is manufactured via the condensation polymerisation of bisphenol and epichlorohydrin. Whereas, epichlorohydrin is produced from propylene as the feedstock by a multi-stage process. Recently, glycerol a by-product of transesterification process is used to produce epichlorohydrin [8]. But, in spite of the utility of the bisphenol, it is considered as a polluting agent and hence research has been carried out to shift to a renewable source like wood or lignin. Nevertheless, there are still some technical limitations such as purity, structural complexity, hydrophilicity and toxicity for which full scale commercial production is a lacuna [9]. Edible oils such as linseed and soybean are currently used largely for the manufacturing of bio-based products due to their sustainability, accessibility and inexpensively [10, 11]. A small quantity of VOs serves as raw materials for the production of various chemical products such as surfactants, lubricants, coatings, and paints. The vegetable oils need to go through structural modifications of the carboxyl groups and double bonded carbon atoms of the triglycerides to be implemented in the production of valuable chemicals. Epoxied vegetable oils (EVO) have been manufactured via the epoxidation of double bonded carbon atoms of the fatty acids of triglycerides by implementing peracids [12, 13]. The widely used industrial peracids are performic acid and peracetic acid which are derived from in-situ production of hydrogen peroxide in the existence of sulphuric acid [14]. To improve the selectivity of the reaction, additives like acidic ion exchange resins, transition metal catalysts, and enzymes are commonly employed. Among these, enzymatic peracids are typically the most effective choice [15–18]. The technique of production of epoxidation greatly influences the its range and the initial iodine value of the final product. Commercially, epoxidized vegetable oils are employed as plasticizers in the manufacturing of polyvinyl chloride (PVC). The policy can be shifted by using EVOs as an alternative feedstock for various epoxy applications as they provide equivalent physico-chemical properties as the petroleum epoxies with renewability and much cheaper cost. However, in spite of potentiality, epoxied vegetable oils are not parallel in application as the petroleum based one owing to technical limitations. Petroleum based epoxies have stiff, aromatic and cyclic-aliphatic structures which imparts required strength to be used as an industrial thermoset plastic. But, EVOs are lacking these structures to confer superior strength in comparison to that of the former. Also, the oxiranyl group present in the EVOs shows comparatively lesser reactivity towards common curing agents such as polyamine or anhydride. However, the recent technology of producing epoxy monomers from vegetable oils tends to show reactivity and structural strength far better than the previously used EVOs. With the employment of new monomers advance utilization can be made possible by the encompassing superior structural and reaction characteristics. Properties are the key criterion for the EVOs to withstand as the alternative resource material for

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the manufacturing of composites at an industrial scale by replacing the conventional fossil fuel based counterparts.

2 Sources Industrial EVOs, being the primary epoxy resins derived from vegetable oils, face inherent challenges arising from their physicochemical structure, flexibility, and relatively slow reaction rate. A large number of thermosetting polymer developed using EVO have inferior glass transition temperature compared to their commercial counterparts and rubbery structures, which inhibits its wide application. Diels–Alder reaction is used to produce functionalized oils using linseed oil and 1,3-butadiene, cyclopentadiene or dicyclopentadiene. Epoxidation of linseed oil is carried out with hydrogen peroxide under catalytic treatment [19, 20]. The development of a cycloaliphatic structure as a result of these changes enhances both the tensile and mechanical strength of the material and leads to an improved glass transition temperature. But the prevalence of the double bonded carbon atoms of the oil requires to be restricted to reduce the formation of high viscous product. By the addition reactive diluents, the viscosity of the product can be minimized in conjunction with the enhanced rate of polymerization and conversion [21]. Webster et al., successfully created highly efficient epoxy compounds through the epoxidation of sucrose esters of fatty acids (ESEFA), which exhibit exceptional structural properties [22, 23]. ESEFA treated with anhydride as the curing agent demonstrated superior thermal and mechanical properties with comparison to the EVOs. Thanks to the internal epoxy groups they contain, ESEFA has proven to be a suitable material for use in cationic treated coatings [24]. However, higher viscosity of the final product inhibits its potential to be used at full scale production. Polyepoxides were produced by conducting a transesterification reaction between soybean oil and ethylene glycol vinyl ether within the structure of poly (vinyl ether of soybean oil fatty acid esters). These polyepoxides exhibited superior kinetics and a higher glass transition temperature compared to epoxy soybean oil (ESO) due to the greater number of epoxy groups present within each individual molecule [25]. Still, restricted molecular mobility due to their structural arrangements and higher viscosity inhibits the applicability in coating industries [26]. In contrast to the inherent oxirane groups found in monomers like EVOs, another type known as terminal epoxy groups, like glycidyl, exhibited improved reaction parameters in nucleophilic curing reactions. The terminal epoxy groups derived from epoxidized triglyceride esters of undecylenic acid were successfully generated and effectively utilized in the curing reactions involving epoxy amine or epoxy anhydride [27, 28]. Owing to the presence of aliphatic structures, the coating materials developed from this method also developed high resilience towards UV radiations [13, 29, 30]. In the cracking reactions, under high temperature and pressure, undecylenic acid is synthesised using castor oil as the feedstock. The fatty acids of the castor oil undergo

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reactions with the glycerol to reform the esters of triglyceride which increases the crosslinking density. But, the oxirane associated with the epoxidized triglycerides was still lower in comparison to the ESO. The treated thermosetting polymer demonstrated little better properties than the widely used ESO or epoxidized linseed oil (ELO) equivalents without having higher alkyl chain compounds. The flexibility of transesterification and epoxidation reactions offers multiple pathways for the production of glycidyl esters of epoxidized fatty acids (EGS). The advantage of using EGS arises due to its high amount of oxirane and lesser viscosity comparative to the ESO or ELO. In a structure–property association study, researchers assessed the impact of the oxirane content and the presence of saturated fatty acids on the polymeric characteristics of the material. Under the cationinc curing treatment, EGS demonstrated higher glass transition temperature way above the ambient room temperature. Still, glass transition temperature higher than 100 °C with superior mechanical and tensile properties can be achieved by the application of curing agents and catalyst.

3 Polymer Structure and Properties It is very essential to understand the structural and physical properties of the VOs and their associations for the designing of epoxy resins [31]. But, the presence of heterogeneous monomers made it extremely challenging to derive a vegetable oil based polymer structure. The composition of the fatty acids shows variations between different vegetable oils along with the intra-variations within a plant. The arrangement and the extent of crosslinking in fatty acids are essential features of a VO based thermoset resin. On the basis of the rubber network elastic theory, the crosslink density can be estimated. Glass transition temperature, which is an exclusive property of epoxy resin observed to be vary within a range of crosslink density. The vegetable oils associated with curing agents vary in their structural properties from rubbery state to plastics depending on chemical and physical properties. The ultimate characteristics of the thermoset polymers are also dependent on various parameters like polymerization conditions, type of catalyst and type and quantity of monomer. The quantity of oxirane and the structure of the monomer have a significant impact on the mechanical and thermal properties of epoxy resin derived from vegetable oils [32, 33]. A terminal epoxy and high oxirane value can direct to faster gelation and greater crosslink density [22, 28]. A reduced oxirane content in epoxidized vegetable oils can lead to either lower reactivity or the imposition of waxy characteristics on the final product [34]. The physical and tensile properties of ESO are inversely related to the crosslink density and chain structures [35]. ESO monomers with highest oxirane value had hardened the polymers possessing lowest elongation at break and higher glass transition temperature with superior thermal resistance in comparison to the low oxirane value based equivalents.

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Owing to the high linolenic components, ELO shows highest oxirane values than other EVOs. As a result, the ELO based thermoset shows superior properties after curing [36]. The anhydride-hardened ESO and ELO displayed a broad distribution of glass transition temperatures, indicating a diverse array of chain environments and heterogeneous polymer structures. This phenomenon can be attributed to the lower reactivity of oxirane groups and the presence of fully saturated fatty acids in these materials [31]. The cationic hardening of thermoset resin showed a linear relationship with the oxirane content. However, linseed oil performed better in comparison to the soybean oil counterparts.

4 Method of Preparation The epoxy group is inserted into the unsaturation sites of the triglyceride molecules by using two routes broadly chemical and enzymatic. Prileshjev reaction is the widely used where in-situ epoxidation of the oil is carried out with peracids [37]. Wool et al., conducted a study on the kinetics of the epoxidation reaction and found that the double bonds in both oleic acid and linoleic acid demonstrated comparable reactivity [38, 39]. Jagtap et al., reported achieving an 80% conversion of double-bonded carbon molecules into epoxy groups under optimized reaction conditions [40]. Hazmi et al., conducted a study, revealing that doubling the concentration of hydrogen peroxide led to a 70% conversion of C–C double bonds into oxiranes in only half the time compared to the previously reported study [41]. Although this method is heavily used in the production of epoxidized vegetable oils, but low selectivity and numerous side reactions attributed into the lower oxirane production [36, 37]. Another method of epoxidation is carried out by using transition metal complexes as catalyst. Guidotti et al., developed a titanium and silica-based transition metal catalyst for the purpose of epoxidizing C19 H36 O2 in the assistance with H2 O2 [42]. As reported by the authors, the novel catalyst high conversion and stereo-selectivity at a temperature of 85 °C maintaining under inert atmosphere. However, employment of lipase catalyst in the epoxidation proves to be advantageous in terms of milder reaction conditions, higher stereo-selectivity and higher conversion [17]. An additional investigation revealed that through meticulous regulation of temperature, peroxide quantity, and enzyme concentration, it becomes feasible to perform the epoxidation of linseed oil by employing a hybrid approach that combines both chemical and enzymatic techniques [43].

4.1 Direct Polymerization of Epoxidized Vegetable Oils In direct polymerization method, vegetable oils are epoxidized by the addition of catalyst. The bio-polymer from soybean oil and epoxidation of castor oil is obtained by

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the catalysis with N benzyl pyrazinium hexafluoro antimonate. The author reported achieving a higher glass transition temperature (Tg ) and a lower coefficient of thermal expansion for castor oil compared to soybean oil. This difference is attributed to the superior intermolecular interactions present in castor oil [44]. Eran et al., achieved the polymerization of ESO by catalyzing it with boron trifluoride diethyl etherate, resulting in a range of Tg from −16 to −48 °C [45]. Meanwhile, Lligadas et al., conducted the epoxidation of methyl oleate in an oligomerization reaction at ambient temperature using fluoroantimonic acid [46].

4.2 Polymerization with Amine as Curing Agents In this method crosslinking agents are employed for the purpose of epoxidation [47, 48]. A bio-based epoxy polymer was produced through the epoxidation of fatty acid derivatives, and it was cured using bis (maminophenyl) methylphosphine oxide as the curing agent. This resulted in a polymer with a high glass transition temperature and excellent thermal stability. The existence of phosphorous molecule in the curing agent attributes in the enhancement of index value of limiting oxygen, which results into high anti-flammability of the resin [27]. A hydrophilic epoxy resin was developed by Ahmad et al., by combining the ELO and diethanolamine employing phthalic anhydride as the curing agent. Apart from being soluble in the water the resin also demonstrated high thermal tolerability [49]. Diamine was used as a hardener by Lapinte et al., for ELO combine with the amidification of fatty acids derived from grapeseed oil, subsequently by the coupling of thiol-ene with cysteamine hydrochloride [50]. It was interpreted that diamines derived from bio-based materials exhibit higher reactivity for ELO in comparison to the commercially available petroleum based one. Additionally the former proved to be more rigid than the latter one. Although epoxy resins develop by the epoxidation of VO with cross linking chemicals as the curing agent demonstrated significant physical characteristics, however they show low chemical tolerability because of their less reactive monomers. As a result, they are preferable as plasticizers and diluents in the manufacturing of epoxy resins from petroleum sources [28, 51]. In another study conducted by Robertson et al., the researchers investigated the hydrolytic degradability and heat characteristics of a resin. The resin was the amalgamation of both bio-based (soybean oil) and chemical-based components. They used diamino-diphenyl-methane as the hardening agent in this study. It was reported that the glass transition temperature of the product resin varies inversely with the ESO amount in the resin [52]. The interpenetrating polymer networks (IPN) was synthesized by using a polyurethane (PU) pre-polymer derived from soybean oil and blending it with a resin made from ESO and diglycidyl ether of bisphenol A (BPA). Their findings indicated that while the glass transition temperature and mechanical properties decreased with

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the addition of the PU pre-polymer, it led to improvements in the breaking and damping characteristics of the final product [53].

4.3 Polymerization with Acid as Curing Agents The literature also suggests the use of acids as curing agents in the production of EVOs. Misra et al., conducted a study where they employed sebacic acid as the curing agent and found that it resulted in better enthalpy and activation energy for the reaction compared to using amines as the curing agent [54]. In the study carried out by Mustata et al., researchers employed acrylic acid and rosin acids as crosslinking agents in creating a resin from a combination of epoxidized corn oil and the diglycidyl ether of BPA. Their results demonstrated that heat characteristics of the resultant resin diminished with an increase in the proportion of epoxidized corn oil [55]. Sibi et al., developed entirely renewable epoxy polymers by using epoxidized sucrose soyate as the feedstock and bio-based dicarboxylic acids as the curing agent, along with DBU as a catalyst. During the reaction, the viscosity was lowered by the interaction between the dicarboxylic acid and the vinyl ethers, which also blocked the reactive sites of the carboxylic acid. This led to an improved affinity of the acids with the epoxy compound [56]. In another study by Matharu et al., a thermosetting resin was prepared taking ELO as feedstock with diacid (Pripol 1009) as the curing agent in the existence of amine catalyst [57]. The product resin was observed to be outstanding in properties such as hydrophobic, physical and calorific stability. A wholly renewable epoxy resin was prepared by Altuna et al., in which ESO is mixed with citric acid in its aqueous form. In this thermally stimulated transesterification reaction of the hydroxyester groups produced throughout the polymerization resulted into the superior properties without the presence of any catalyst [58].

4.4 Polymerization with Anhydride as Curing Agents Anhydrides are also used to copolymerize the vegetable oils implementing the same method corresponding to that of commercially produced resin [59]. Chow et al., conducted an investigation that unveiled the kinetic parameters involved in the reaction between ESO and methylhexahydrophthalic anhydride (MHHPA) when catalyzed by 2-ethyl-4-methylimidazole (EMI). The combination of ESO and MHHPA displayed autocatalytic characteristics throughout the entire duration of the isothermal curing process. The reported activation energies for the reaction was tend to be declined with the increase in the dosage of the EMI catalyst. The observed conversion was varied between the range of 60–80% depending on the temperature of the curing and dosage of EMI catalyst [60].

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Curtis et al., manufactured thermosetting epoxy polymers by utilizing epoxidized canola oil (ECO) and employing phthalic anhydride as the curing agent. The resin displayed varied mechanical characteristics of rigidity and flexibility. It was reported that although the calorific properties of the resin was not influenced by curing temperature, however, the process of curing hastened up with the increasing temperature. The higher amount of the curing agent adequately effected the reaction rate and glass transition temperature of the final product [61]. A renewable epoxy resin was developed using ESO and maleic anhydride as the curing agent [62]. As stated by the authors, the crosslinking density and physical characteristics of the resin was greatly influenced by the weight ratio of ESO and maleic anhydride. Zhang utilized dicarboxylic acids produced by mixing fatty acids from oil with acrylic acid and fumaric acid. These acids were subsequently transformed into diand triglycidyl esters by incorporating epichlorohydrin. The combination of these monomers with the curing agent nadic methyl anhydride exhibited enhanced physicochemical properties when compared to materials prepared using commercial BPA [63]. Webster et al., in a comparative study among different epoxy resins found that the one prepared from sucrose-based materials demonstrated high rigidity owing to their cyclic structural arrangements [64]. Usually, aliphatic anhydrides result in the creation of pliable and elastic resins, whereas rigid-ring anhydrides yield solid thermosetting polymers. To achieve a combination of both properties, the blending of two types of anhydrides has been employed. Carbonell-Verdu formulated a range of thermosetting epoxy polymers from epoxidized cottonseed oil by employing a blend of a solid anhydride and a pliable anhydride with an extended side chain (dodecenyl succinic anhydride) as the curing agent. The resulting resin exhibited the desirable characteristics of both types of hardeners [64]. In another study conducted by Samper et al., the researchers formulated epoxy resins from EVOs by employing a combination of phthalic anhydride and maleic anhydride as hardeners, with varying ratios of ESO and ELO. Their findings indicated that the glass transition temperature and flexural properties exhibited an inverse relationship with the quantity of ESO used, while the coefficient of linear expansion increased as the amount of ESO in the resin increased [65]. EVOs are additionally exposed to copolymerization with epoxy derived from petroleum to enhance the characteristics of the resultant resin. Stefani formulated a resin by partially replacing the diglycidyl ether of BPA with ESO, and utilized methyl-tetrahydrophthalic anhydride as the curing agent. The author noted the lower reactivity of the oxirane rings in ESO due to steric hindrances. As the amount of ESO increased, the glass transition temperature decreased, but the storage modulus remained constant in the rubbery state [66].

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5 VO Based Epoxy Composites Epoxidizing VOs holds great promise in the creation of epoxy resins derived from VOs. This method introduces an oxirane ring, acting as a terminal group in triglycerides, imparting heightened reactivity and ultimately converting these oils into valuable, polymerizable components [67]. Numerous research investigations have delved into the direct production of epoxy resins using a range of EVOs, including ESO [2, 54, 68], epoxidized hemp oil [69], ELO [70], and various others. Certainly, it is a widely acknowledged fact that epoxy resins originating from vegetable oils often exhibit deficiencies in terms of desirable properties, notably a low Tg . This constraint is likely attributed to inadequate crosslinking within the epoxy matrix, primarily arising from incompletely reacted EVOs and residual fatty acid chains [71]. This undesirable characteristic inhibits the application of VO based expoxies to be used in high strength requisitions and limited its usage in coating and additives [72].

5.1 Utilizing Bio-Based Hardener in VO Epoxy-Based Resin The exploration of VO-based epoxy resin in combination with a bio-based hardener presents an exciting opportunity to advance the field of bio-based epoxy networks. However, it is important to highlight that the prevailing body of research has mainly focused on comparing bio-based epoxy resins derived from VOs with bio-based hardeners in contrast to their petrochemical-based equivalents. This emphasis likely stems from the observed limitations in the thermo-mechanical properties of the former. Stemmelen et al., [71] accomplished a significant achievement by formulating a completely bio-based epoxy resin derived from ELO and curing it with a biobased epoxy hardener obtained from grapeseed oil (GSO). The synthesis process involved the use of cysteamine chloride (CAHC) in a thiol-ene coupling (TEC) reaction, as illustrated in Fig. 1. The authors conducted an in-depth study of the heatinduced cross-linking between a polyamine derived from grapeseed oil (AGSO) and ELO. When comparing the cured AGSO–ELO resins with those cured using methyl tetrahydrophthalic anhydride (MTHPA), they made an interesting discovery. The AGSO–ELO resins displayed notably lower glass transition temperatures (Tg ). This finding suggests that epoxy resins based on vegetable oils contribute to the lower Tg of the resulting materials, which in turn affects their mechanical properties. The lower Tg suggests a decreased cross-linking density, which is probably attributed to the higher molecular flexibility of the AGSO curing agent in comparison to MTHPA. The same researchers had previously undertaken a study aimed at developing bio-based epoxy resin by incorporating epoxidized linseed oil (ELO) and various fatty amides and diamides [50]. In another study, they examined the use of AGSO as a curing agent, in conjunction with a commercially available curing agent called Priamine. The objective of the research was to cure the bio-based epoxy resins

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Fig. 1 The amination reaction of GSO using CAHC carried out through UV-initiated thiolene coupling

obtained from ELO and assess their thermo-mechanical properties. Following an extensive analysis, the researchers concluded that the ELO-based epoxy resin system, when cured with aminated fatty amide (AFA), exhibited superior performance when compared to other commercially available fatty amides, including Priamine. The assessment was based on data from Differential Scanning Calorimetry (DSC) and dynamic rheological analysis, which showed promising results for the ELO-based epoxy resin with AFA as the curing agent. The study of different epoxy-soybean oil (ESO) formulations, each cured with a specific compound: terpene-based acid anhydride (ESO–TPAn), hexahydrophthalic anhydride (ESO–HPAn), maleinated linseed oil (ESO–LOAn), and a thermally latent cationic polymerization catalyst (ESO–CPI). The research aimed to evaluate their thermal, mechanical, and biodegradable properties [2]. According to the Differential Scanning Calorimetry (DSC) data, it was noted that the ESO–TPAn system exhibited a higher Tg when compared to others. One possible reason for this difference could be attributed to the replacement of the cyclohexene portion in TPAn with a bulkier CH2 =C(CH3 )2 group and the existence of two methyl groups within the ESO–TPAn formulation. In their research, Kadam et al., employed an epoxidation process involving hydrogen peroxide and acetic acid to produce a bio-based epoxy resin using karanja oil [73]. Subsequently, they introduced two bio-based acids, citric acid (CA) and tartaric acid (TA), into the epoxidized oil (TAR). Remarkably, the researchers discovered that the thermal stability of the resulting bio-based resins were comparable with that of petroleum-based epoxy resin. The thermal decomposition temperatures for these bio-based resins were measured at 280 and 295 °C, respectively, surpassing the degradation temperature of comparable diglycidyl ether of BPA (DGEBA) resins, which typically degrade at 125 °C. Darroman et al., innovatively developed a bio-based epoxy hardener using cardanol, and this hardener was functionalized with cysteamine through a process known as TEC (thiol-ene coupling) [74]. This newly formulated product demonstrated thermo-mechanical characteristics on par with conventional epoxy hardeners. What sets these bio-based resins apart is that they were produced using a safer and more environmentally friendly method, specifically the Mannich reaction. This approach eliminated the need for hazardous amines or formaldehyde while utilizing phenolic compounds. The study involved comparing the curing behavior of resins using commercially available cardanol-based amine agents and the newly developed cardanol-based amines. The thermogravimetric analysis (TGA) results revealed that the former resin degradation at approximately 325 °C, whereas the latter one began to

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degrade at around 328 °C. These observations were made under a nitrogen environment, with the degradation starting at the 10% mark of the total degradation process. This indicates that the weight loss was more rapid when using the commercially available cardanol-based amine agents in comparison to the new cardanol-based agents. Furthermore, the results from DSC indicated that the Tg of the commercial cardanolbased amine agent was 30 °C, whereas the new cardanol-based amine agent had a Tg value of 19 °C. The variation in Tg values can be explained by the reduced degree of functionalization in the commercially available cardanol-based amine agent in contrast to the newly developed agent. Table 1 provides a comprehensive overview of the thermo-mechanical characteristics of various vegetable oil/epoxy resin combinations featuring bio-based hardeners. The data in the table suggests that the attributes of VO-based epoxy resin are influenced by a range of factors, including the particular vegetable oil composition, the choice of ring-opening agent, the degree of epoxidation of the vegetable oil, and the specific type of epoxy resin employed. Notably, the VO-based epoxy resin displays exceptional properties, including a greater cross-linking density, a higher Tg , and increased tensile strength, which can be attributed to the elevated functionality of the VO component.

5.2 Blending Bio-Based Hardener with VO-Based Epoxy Resin As previously discussed, the synthesis of epoxy resins directly often results in less than ideal physicochemical properties, which can bound their attractiveness in the market. The effectiveness of a polymer largely depends on its Tg being higher than the anticipated operating conditions. To address this challenge, researchers have investigated the possibility of blending conventional petroleum-based epoxy resins with epoxidized vegetable oils. By partially substituting the high viscosity of petroleumbased epoxy resins with functionalized VOs, it becomes possible to produce materials that exhibit desirable properties, cost-effectiveness, and improved process ability [77]. Several references have extensively explored the combination of vegetable oils (VOs) with epoxy resin, specifically DGEBA, and have reported significant findings [78, 79]. The incorporation of VOs into epoxy resin has generally led to an improvement in the toughness properties of the resultant resin system [79, 80]. When biobased resins contain a higher content of VOs, they exhibit enhanced impact energy absorption. This improvement can be attributed to the long, flexible, and resilient network structure of VOs, which enhances the mobility of the resulting resins, thereby increasing fracture initiation and propagation resistance [81]. However, it is essential to note that the addition of epoxidized VOs to the bio-based resin system also leads to a reduction in tensile and flexural characteristics. The decrease in strength can be ascribed to the weaker interphase interaction between VOs and epoxy networks. This

Citric acid Tartaric acid

Commercial cardanol based amine New cardanol-based amines (cardanol cysteamine)

Tannic acid

Epoxidized karanja oil

Epoxidized cardanol NC-514

Epoxidized soybean oil 63 °C < Tg < 90 °C

19–30

109–112.7

23–60

–

Citric Acid: 10.60, Tartaric acid : 4.50

1.1–8.8

Dicarboxylic acid Pripol 1009

Epoxidized linseed oil

−15.1–7

Terpene-Based anhydrides

Epoxidized soybean oil