For natural fiber-reinforced composites

The inherent polar and hydrophilic nature of lignocellulosic fibers and the nonpolar characteristics of most thermoplastics results in compounding difficulties leading to non-uniform dispersion of fibers within the matrix, which impairs the efficiency of the composite. This is a major disadvantage of natural fiber-reinforced composites. 

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Maleated coupling agents are also widely used to strengthen composites containing fillers and fiber reinforcements. Interactions 

Reinforcement Processing Fiber Tensile Young s Flexural Impact content strength modulus strength strength (%) (MPa) (GPa) (MPa) (KJ/m )  

Aydin et al. reported the influence of alkali treatment on the mechanical, thermal, and morphological properties of eco-composites made by short flax fiber reinforced PLA Scanning electron microscopy (SEM) revealed that the packed structure of the fibrils was deformed by the removal non-cellulosic materials. The mechanical tests indicated that the modulus of the untreated flax fiber/PLA composites was higher than that of PLA on the other hand, the modulus of alkali treated flax/PLA was lower than that of PLA. Thermal properties of the PLA in the treated flax fiber reinforced composites were also affected. Tg values of treated flax fiber reinforced composites were lowered by nearly 10°C for 10% NaOH treatment and 15°C for 30% NaOH treatment. A bimodal melting behavior was observed for treated fiber composites different than both of neat PLA and untreated fiber composites [60]. 

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The lower thermal stability of natural fibers, up to 230°C, the thermal stability is only small, which limits the number of thermoplastics to be considered as matrix materials for natural fiber composites. Only those thermoplastics whose processing temperature does not exceed 230°C are usable for natural fiber reinforced composites. These are, most of all, polyolefines, such as polyethylene and polypropylene. Technical thermoplastics, such as poyamides, polyesters, and polycarbonates, require... 

The commercial application of natural fiber reinforced composite systems compared on Table IV is extremely rapidly growing in the automobile manufacturing. Figure 4 shows the conceivable applications for natural fiber reinforced composite in a typical European passenger car [12], Similar application can be designed in commercial heavy transporter (see Fig. 5). 

Bos H, Van den Oever M, Peters O (2002) Tensile and compressive properties of flax fibers for natural fiber reinforced composites. J Mater Sci 37(8) 1683-1692... 

As previously mentioned, the incorporation of reinforcements such as natural fibers is one of the interesting approaches to enhance the properties of polymer composites, which can address the significant requirements of most engineering applications. For this reason, the demand for natural fiber-reinforced composites has increased dramatically over the past few years for various commercial applications [6]. The increasing number of publications in recent years reflects the growing importance of this type of composite. Figure 22.1 shows the number of journals published about natural fibers and polymer composites over the past five years. Up to now, studies have established a rough indication of the increased interest of researchers on this topic. The natural fibers... 

The strength of the fiber is very important for natural fiber-reinforced composites. Polar natural fibers are inherently incompatible with hydrophobic polymers. Therefore, the surface modification of natural fibers is required to improve its physical and chemical properties. Various chemical treatment methods have been used to modify the surface properties of the natural fibers. Few methods of surface modification are described below ... 

K. Williams. Automotive industry uses of natural fiber reinforced composites. In The Global Outlook for Natural Fiber Wood Composites 2003, Intertech, New Orleans, LA, December 2003. 

Thielemans, W. and Wool, R.P. (2004) Butyrated kraft lignin as compatibilizing agent for natural fiber reinforced thermoset composites. Composites Part A Applied Science and Manufacturing, 35,327-338. Satheesh Kumar, M.N., Mohanty, A.K., Erickson, L. and Misra, M. (2009) Lignin and its applications with polymers. Journal of Biobased Materials and Bioenergy, 3, 1-24. 

Christian, S.J. and Billington, S.L. (2011) Mechanical response of PHB- and cellulose acetate natural fiber-reinforced composites for construction applications. Composites Part B, 42 (7), 1920-1928. 

Xue L, Tabil LG, Panigrahi S (2007) Chemical treatments of natural fiber for use in natural fiber reinforced composites a review. J Polym Environ 15 25-33 Yanai Y Non-resin shrink-proof process, Caltopia. Nisshinbo Industries Inc. Miai Plant, Aichi, Japan (unpublished)... 

X. Li, L. Tabil, and S. Panigrahi, Chemiccil treatments of naturcd fiber for use in natural fiber-reinforced composites A review. J. Polym. Environ. 15(1), 25-33 (2007). 

S. Chappie, and R. Anandjiwala, Flammability of natural fiber-reinforced composites and strategies for fire retardancy A review. /. Ihermoplast. Compos. Mater. 23,871-893 (2010). 

Kumar et al. [83] studied the weathering properties of ethylene-propylene copolymer (EPC) matrix composites with three different reinforcement materials, namely, 3% NaOH-treated jute fibers, 17.5% NaOH-treated jute fibers and commercial microcrystalline cellulose powder, using maleated EPC as a compatibilizer. The samples were subjected to UV radiation at 60°C in air for 150 hours. Again, the neat polymer samples were more resistant to weathering than the composites. The samples reinforced with commercial microcrystalline cellulose were the most stable of the composites and those made with fibers treated with the lower concentration of NaOH were the most susceptible to photo-oxidation. It was concluded that optimizing the durability and mechanical properties of the natural fiber-reinforced composites was closely dependent on selecting the appropriate treatment for the fibers. 

One increasingly important property for interior components in automotive applications, where natural fiber-reinforced composites have performance advantages, is the acoustic absorption. Natural fiber-reinforced composite materials in an interior component have an open cell structure. It will therefore contribute to sound absorption and may result in a reduced need for absorbers. Multilayer components further offer many possibilities to tailoring the acoustic absorption of the system. 

All bast (stem) fibers (flax, kenaf, ramie, nettle, hemp, jute) as well as hard fibers (caroa, sisal) are suitable as for reinforcing fibers for natural fiber reinforced polymer composites, if they have a high tensile modulus and sufficient tensile strength. In addition to cultivation site, type and harvest, the properties of natural fibers depend significantly on the fiber extraction method. An extraction to technical fiber grades, i.e. production of bundles with different number of single fibers, is generally sufficient for use in plastics composites. The properties of such extracted fibers may be described as follows ... 

Due to the increasing commercial interest for natural fiber-reinforced polymer composites as well as demands for environment friendly materials, the development of fully biodegradable plant fiber-PLA composites is on the rise. Different natural plant fibers have been employed with PLA to produce composites. The most studied natural fiber reinforcements for PLA were kenaf [10, 21-23], flax [24, 25], hemp [26], bamboo [27], jute [28], abaca [29], pineapple leaf [9], and wood fibers (WF) [30, 31]. In addition to these conventional plant fibers, recently reed fibers have been used for preparation of PLA composites [31]. 

Interest in natural fibers obtained from different resources to reinforce polymer so as to get the novel composites is growing rapidly because they are renewable, cheap, recyclable, and biodegradable. Research in this field has prompted surface modification of natural fibers in order to improve the compatibility between hydrophilic fibers and hydrophobic matrix [1], Major challenges for polymer scientists in the development of structural natural fiber-reinforced composites are to increase the moisture resistance, dimensional stability with minimized matrix material, and to decrease the manufacture costs of the composite materials. Different researchers have used different surface modification methods, that is, mercerization [2], benzoylation [3], silanation [4], acetylation [5], graft... 

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