Abstract
Increased environmental concerns and global warming have diverted effort all over the world to focus on renewable and sustainable resources for the next generation of composite products due to their recyclability, renewability, cost effectiveness, and satisfactory mechanical performance. Bio/natural fibers which are environment friendly materials employed as reinforcement have led to developing a biocomposite for reduction in greenhouse emission and carbon footprints. However, biofibers are also having some limitations that need to be addressed including poor compatibility between the reinforcing fiber matrices, high moisture absorption, swelling, poor chemical and fire resistance, and high dispersion of mechanical properties. A lot of research has been performed on physical and mechanical properties of natural fiber composite. Properties of such novel composite mainly depend on adhesion between fiber and matrices. Consequently, poor adhesion, high moisture absorption, and swelling lead to formation of crack in both the matrix and fiber. Therefore, numerous techniques have been tried till date to modify both fiber surfaces to enhance their adhesion and reduce their water absorption. This review article provides comprehensive information about effect of various surface modification techniques that include alkaline, silane, acetylation, permanganate, peroxide, benzoylation, acrylonitrile grafting, maleic anhydride grafted, acrylation, and isocyanate. In addition, the effects of cellulose, hemicellulose, lignin, and pectin of biofibers are also reported. This review concluded that chemical treatment of biofibers with 5% NaOH concentration improves the physical, mechanical, and thermal properties of the resulting composites compared to untreated fiber composites.
Highlights
The automotive industries do face many challenges, such as the shortage of supply of fossil fuels, new technological innovations, and environmental sustainability to fight global warming. e above listed factors increase the pressure in the current materials design and manufacturing technologies in automotive industries [1, 2]
A lightweight material was a necessity for the structural components for lower energy consumption of vehicles. e research community has shifted the focus towards effective utilization of the biofibers extracted from renewable sources. e natural fibers are being employed for application components such as interior dashboard trims for automobiles and household applications [3, 4]. e utilization of lightweight and lowcost biofibers such as abaca, banana, bamboo, coir, flax, ramie, tea leaf, pineapple, sisal, kenaf, and jute was already tried as reinforcements in the polymer matrix for composite materials used for manufacturing automobile components [5,6,7]. e biodegradability of biofibers is associated with physical, chemical, mechanical, thermal, and moisture conditions which have increased their scope of use in numerous applications [8, 9]
The water absorption and thermal stability of the composite laminate were noticed to reduce with increase in weight fraction of fiber [24,25,26,27,28]. e natural fibrils are constituted of cellulose, hemicellulose, and lignin in varying percentages
Summary
The automotive industries do face many challenges, such as the shortage of supply of fossil fuels, new technological innovations, and environmental sustainability to fight global warming. e above listed factors increase the pressure in the current materials design and manufacturing technologies in automotive industries [1, 2]. E utilization of lightweight and lowcost biofibers such as abaca, banana, bamboo, coir, flax, ramie, tea leaf, pineapple, sisal, kenaf, and jute was already tried as reinforcements in the polymer matrix for composite materials used for manufacturing automobile components [5,6,7]. E major disadvantages of natural fiber are poor adhesion between fiber and matrix, presence of cellulose content, moisture absorption, and voids at interface between fiber and matrix which results in dimensional inaccuracy, affecting the mechanical properties [32,33,34,35]. E chemical treatments are carried out to reduce the hydrophilic nature of fiber but the surface treatments modify the fiber surface and increase the fiber strength leading to the improvement of adhesion between fiber and matrix [36,37,38]. Recent literature survey showed that several works have been published on different natural fibers extracted from renewable sources which are used as reinforcement with polymer matrix over a wide dimension of applications. is survey depicts various surface treatments done to enhance the properties of the fibers and for enrichment in mechanical properties of the composites in contrast with untreated fiber-reinforced polymer composites. erefore we summarized the major findings on different types of chemical treatments and surface treatments
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