Natural plant fibers

Cordage and fabric are made from natural plant fibers that come from different parts of various plants. Table 4.3 lists some of the most common plant fibers used to make fabric and cordage. 

U.S. Pat. No. 6,983,571 [73] discloses a composite roofing panel comprising polyethylene, polypropylene, or a combination thereof in an amount of 20-40% by weight, and natural plant fiber in an amount of 40-75%, selected from the group consisting of wood flour, sugarcane bagasse, hemp, coconut coir, jute, kenaf, sisal, flax, coir pith, rice hulls, and cotton. 

The basic raw material is cellulose, a major constituent of sawdust, straw, cardboard or paper wastes, wood chips, or other natural plant fibers. Any of these materials should be chopped or shredded, but never so finely as to eliminate their inherent structural qualities. This cellulosic base comprises approximately 80% of the total substrate mixture. 

Composites are engineered materials that contain two or more constituents with different properties that remain distinct from one another within the structure. POCs are a subset of the larger polymer composites group. The increased synthesis of POCs with different additives is necessary to satisfy the industrial demand that cannot be fulfilled by pure polymers. Additive materials can be classified as micro-and nanofillers depending on the applications of the composites. The fillers may be further subdivided as natural (plant fibers) or synthetic (glass fibers, CNT, etc.), different shapes (long or short length), flaky, fibrous, and spherical or disk-like [6]. The conventional addition of filler materials lowers the cost and improves the... 

In case of utilization by combustion, polymeric composites reinforced with natural plant fibers emit less CO2 than chemical fibers (Bledzki 1997). The composites based on natural fibers and synthetic polymers such as PE, PS, PP, etc. are called biocomposites, and being eco-friendly can contribute to solving numerous enviroimiental problems. 

F. 4.6 Natural plant fiber used in cxnnpany cars Daimler-Benz 65... 

The properties of a composite are dictated by the intrinsic properties of the constituents which may be summarized as fiber architecture and fiber-matrix interface (Fowler et al. 2006). The reinforcing efficiency of natural fibers depends on their physical, chemical, and mechanical properties. Major shortcomings of natural plant fibers include fiber nonuniformity, property variation even between individual plants, low degradation temperature, low microbial resistance, and susceptibility to rotting. In addition to naturally occurring nonuniformity, fiber extraction and processing techniques also have major impacts on final fiber quality, not to mention fiber costs and yield (Munder et al. 2005). 

The amount of cellulose in lignocellulosic systems, can vary depending on the species and age of the plant. Table 21.1 shows the chemical composition of some common natural plant fibers. 

Wood as a form of natural plant fiber is a composite material in which the cellulose fibers as reinforcing elements are embedded in the lignin matrix. It is used as fuel or as a construction material, for packaging, artworks, and paper. Lignins are aromatic amorphous oligomers of di- and trisubstituted phenyl propane units obtained from the wood as by-products of the pulp and paper industries by solvent extraction. Lignin can be used after fractionation as fillers or as antioxidants and can be modified by esterification [105,106],... 

The formation of fibers from natural or synthetic materials depends on some specific factors. A material must have the correct plastic characteristics that allow it to be formed into fibers. Without exception, all natural plant fibers are cellulose-based, and... 

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]. 

Figure 3.2 Structural hierarchy of natural plant fiber down to molecular level.

The structure and properties of biofibers, mainly of cellulose, were described in this chapter. First, the hierarchy microstructure of natural plant fiber and then a variety of crystal modifications of cellulose were mentioned. The ultimate mechanical properties (modulus of 138 GPa and strength of 17.8 GPa) and thermal properties (thermal expansion coefficient of 10 order) were emphasized as quite excellent for cellulosic fiber, enough for use as reinforcement in the composites. With the manifestation of these intrinsic properties in macroscopic material, the oH-cellulose composite was shown to possess excellent mechanical properties, thermal resistance, and optical transparency, besides being composed of fully sustainable resources and hence, biodegradable. Nowadays, the interest in cellulosic nanocomposites has increased considerably [60, 61] and they are expected to be used in many fields such as electronic devices, vehicles, and windmills to replace glass and/or carbon fibers. 

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