Kenaf fiber structure

D. Feng and A.R. Sanadi. Effect of compatibilizer on the structure-property relationships of kenaf fiber-polypropylene composites. In Fourth International Conference on Wood-flber-Plastic Composites, Madison, WI, May 12-14, 1997, pp 157-160. 

The secondary wall found in wood cells is composed of two or three layers, known as SI, S2, and S3, respectively. In each of these layers, the cellulose microfibrils are "spirally-wound" at a different angle to the major axis of the tracheid. This variation in microfibril angle imparts strength to the fiber structure in a variety of directions. Within the bast or schlerenchyma cells found in flax, hemp, jute, and kenaf, the secondary wall is less thick than that of wood, but contains layers of similarly spirally-wound microfibrils embedded in a hemicellulose and pectin-rich matrix. This "composite structure" imparts potentially high strength to regions of the cell wall. Figures 9.1 and 9.2 show a schematic representation of flax fiber and a section of an elementary fiber with its fibrillar structure in its secondary cell wall [31]. 

Stout has written a detailed review on jute and kenaf. X-ray diffraction patterns show the basic cellulose crystal structure, although in jute and kenaf the crystalline orientation is high and the degree of lateral order is lower than in flax. Batra" in a comprehensive review has highlighted the morphological structures and physical, mechanical and chemical properties of other long vegetable fibers. 

Kenaf is now being grown in several countries where the bast fiber is used for geotextiles and the pith is going into sorbents for oil spill clean up and animal litter. The production of pulp and paper from kenaf is growing, but it is only used for limited types of papers at present. The utilization of the whole plant of both jute and kenaf is under consideration for structural and nonstructural composites. Automotive interior door panels are now produced in Germany and the United States out of jute and kenaf bast fiber in combination with thermoplastics. 

The x-ray diffractograms showed the presence of cellulose I structure in all raw fibers. In the treated banana fiber, cellulose II structure was dominant. While cellulose I ([002] peak) is found in all five raw fibers, the [002] peak cellulose II is found as a shoulder in kenaf and ramie. The measured crystallinity (x%) in raw and alkali-treated fibers are shown in the table below ... 

The mechanical properties of bast fibers, especially flax, hemp, kenaf, and jute, are very good and may successfully compete with glass fiber. Their characteristics are strongly related to the structure and composition. 

Nakagaito AN, Yano H (2005) Novel high-strength biocomposites based on microfibrillated cellulose having nano-order-unit web-like network structure. Appl Phys A 80 155-159 Nakagaito AN, Yano H (2008) The effect of fiber content on the mechanical and thermal expansion properties of biocomposites based on microfibrillated cellulose. Cellulose 15 555-559 Nishino T, Hirao K, Kotera M, Nakamae K, Inagaki H (2003) Kenaf reinforced biodegradable composite. Compos Sci Technol 63 1281-1286... 

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