Properties of Plant Fibers

Exploiting natural fibers from agro-residues brings a new question that whether these fibers characteristics would let them to act as effective reinforcement elements for utilization in composites [15]. This necessitates close study of the characteristics of agro-residual fibers. Accordingly, Table 11.5 lists characterization methods applied on agro-residual fibers. 

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The mechanical and physical properties of plant fibers are also influenced by the following structure parameters [17,21] ... 

Cellulose is found not to be uniformly crystalline. However, the ordered regions are extensively distributed throughout the material and these regions are called crystallites [27]. Cellulose exists in the plant cell wall in the form of thin threads with an indefinite length. Such threads are cellulose micro-fibrils, playing an important role in the chemical, physical, and mechanical properties of plant fibers and wood. 

The properties of plant fibers can be modified through physical and chemical technologies to improve performance of the final biocomposite. Some of the plant fibers with suitable properties for making biocomposites are summarized in Table 4.11... 

Mishra S, Naik JB, Patil YP (2000) The compatibilising effect of maleic anhydride on swelling and mechanical properties of plant-fiber-reinforced novolac composites. Compos Sci Technol 60(9) 1729-1735... 

Hill CAS, Khalil HPS, Hale MD (1998) A study of the potential of acetylation to improve the properties of plant fibers. Ind Crops Prod 8 53. http //www.thefreelibrary.com/Natural... 

In this section, first, the relationship between NaOH concentration and mechanical properties of plant fibers is discussed using X-ray analysis. Further, the effect of alkali treatment on the mechanical properties of ramie fiber-reinforced composites is explained. 

The angle of the fibrils and the content of cellulose determine the properties of the plant fibers. The Hearle et al. s model [19] considers only these two structure parameters. For the description of stiffness, solely, the St layers were considered because the properties of these fibers were decisively dominated by the amount of these layers. 

When used as substitutes for asbestos fibers, plant fibers and manmade cellulose fibers show comparable characteristic values in a cement matrix, but at lower costs. As with plastic composites, these values are essentially dependent on the properties of the fiber and the adhesion between fiber and matrix. Distinctly higher values for strength and. stiffness of the composites can be achieved by a chemical modification of the fiber surface (acrylic and polystyrene treatment [74]), usually produced by the Hatschek-process 75-77J. Tests by Coutts et al. [76] and Coutts [77,78] on wood fiber cement (soft-, and hardwood fibers) show that already at a fiber content of 8-10 wt%, a maximum of strengthening is achieved (Fig. 22). 

Properties of cellulose fiber will be considered in more detail in the next section and at the description of specific plant materials. 

In this chapter an attempt has been made to discuss the methods available for the isolation and analysis of higher plant cell walls. Because the structures and properties of the cell wall polymers from various tissue tyjDes show considerable differences, it is emphasized that, where possible, separation of the tissues in a plant organ prior to preparation of the cell walls is desirable. Attention is drawn to the problems associated with coprecipitation of intracellular compounds with cell wall polymers, particularly in view of the occurrence of small amounts of proteoglycan and proteoglycan-polyphenol complexes in the walls and the covalent attachment of phenolics and phenolic esters with some of the cell wall polymers of parenchymatous and suspension-cultured tissues. The preparation of gram quantities of relatively pure cell walls from starch- and protein-rich tissues is discussed at some length because of the importance of dietary fiber in human nutrition and an understanding of the composition, structure, and properties of dietary fiber would be hampered without such methods (Selvendran, 1984). 

Recent patents describe the use of solvents to improve the properties of agricultural chemicals. In one invention, a carrier was developed from an agglomerated composition of plant fibers and mineral filler. The purpose of the carrier is to absorb and hold a large quantity of pesticide until it is delivered to the application site. The pesticide must be in a form of low melting liquid. In order to reduce its melting point, solvents selected from aromatic hydrocarbons are used to dissolve pesticide. In a water dispersible composition of insecticide, solvent is used to convert insecticide to a liquid form at room temperature. Solvents proposed for this application are from a group of aUcyl aromatic hydrocarbons, methyl esters of alkanoic acids, and ester mixtures derived from plant oils. 

There are many reports in scientific literature that present data determining physical-mechanical properties of bast fibers. The properties of the fiber are related to varieties of fibrous plants, condition of cultivation and retting, as well as the condition of measurement. Natural fibers are also characterized by the variability of individuals and from these reasons it is possible to find some differences between the fiber properties given by different authors in literature. 

In order to utilize sisal fiber for electrical apphcatimis, several researchers have studied different electrical properties of sisal fiber at different temperatures and frequencies. The work carried out by Xin et al. [138] showed that an increase in frequency decreases the dielectric crmstant e whereas an increase in temperature increases at all frequencies. Increasing the plant age shifts the dissipation factor (tan 5) peak to higher temperature. 

Sharma D (2004) India automotive components industry, Swiss Business Hub India, pp 1-20 Sink SE (2005) Specials reported cars made of plants, http //www.edmunds.com Bolton J (1997) Plant fibers in composite materials a review of technical challenges and opportunities. The Burgess-Lane Memorial Lectureship in Forestry, March 5 138. 3 X, Xu CG, Qing LF (2007) Friction properties of sisal fiber reinforced resin brake composites. Wear 262 736-741... 

Coir fibers are obtained from the husk of the coconut. Coir fiber is generally extracted by mechanical means from the plant [52]. Manilal et al. [52] extracted coir fibers by a closed retting process in an aerobic retting reactor. Bakri and Eichhorn [53] mechanically extracted coir and celery fibers and studied their tensile behaviors in terms of micromechanics. Mothe and Miranda [45] studied the thermal stability and chemical constituent analyses of coir fibers. Khan and Alam [54] investigated the effects of several chemical treatments on the thermal and meachanical properties of coir fibers. Mahato et al. [55] studied the effect of alkalization on the thermal degradation of coir fibers. 

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