Comprehensive evaluation of kenaf as an alternative fiber for paper and wood composites

Search for non-woody, strong, recyclable and economical natural fibers provided motivation for this research. The study examined the fiber properties of four kenaf cultivars namely: Everglades 71, Tainung-2, SF-459 and 7N. The plants were grown in four sites in Texas and Illinois in 1994 and 1995. Results showed that the fiber lengths, widths, and length to width ratios of the four cultivars were not significantly different. What contributed to differences in fiber properties were the location of growth and the sources of fibers along the stem length and within the plants. Bark fibers from the middle section of stems were significantly longer than those from the bottom of the plants. On the other hand there was no significant difference among core fibers along the stem length. Fiber width remained uniform along the stem.; Kenaf fibers showed high sulphur content and low heat of combustion as compared to hardwoods. Bark fibers exhibited lower sulphur content than core fibers when compared with hardwoods. Hollocellulose amount in kenaf fibers was similar to hardwoods but alpha-cellulose and alcohol benzene extractives were higher than hardwoods. Cultivars SF-459 produced strongest fibers and Everglade produced weakest. Kenaf fibers showed elongation of 2% to 3.2% and a wide variation in water of imbibition values. Cultivar 7N had the strongest correlation of fiber strength and chemical composition.; Kenaf-aspen boards produced board properties similar to or better than those of commercial oriented strandboard. The specific gravity of these boards varied from 0.68 to 0.75. Moisture content was slightly higher for kenaf flakes as compared to commercial aspen flakes prior to the board making. Amount of kenaf, board construction, direction of flakes, glue content and density significantly affected the modulus of rupture and modulus of elasticity values of boards. The 6% resin and 42 pcf density performed better than 6% and 46 pcf density. Boards with 25% kenaf and 75% aspen were the best. Kenaf and glue levels were significant factors influencing the internal bond strength. The 25% kenaf and 75% aspen boards gave the best results. Boards with 50% to 100% kenaf flakes had similar internal bond strength. Kenaf percentage and resin content contributed significantly towards the hardness of boards. In general lower percentage of kenaf flakes and higher percentage of glue produced high hardness values.; Kenaf-aspen boards produced lowest values for linear expansion although no significant factor contributed towards linear expansion. Homogeneous boards performed better in linear stability than the 3-layered boards. Higher percentage of kenaf flakes gave lower values for linear recovery, thickness recovery and high values for moisture intake. Percentage of kenaf flakes and resin content controlled thickness swelling after 24 hours in water. The 100% kenaf boards showed higher thickness swelling and the boards with 25% kenaf and 75% aspen flakes had minimal thickness swelling. High resin content tends to reduce thickness swelling. Thickness swelling for boards with 25% to 75% kenaf flakes was less than 15%.