Effect of Pellet Geometry and Water Absorption on Strength of Long Jute Fiber Reinforced Polypropylene
Kazuhiro SHIMA, Hironori MIZOGUCHI, Kazuya OKUBO, Toru FUJII and Tatsuya TANAKA
Abstract: Effect of the twisting direction, pellet fiber length and water absorption on the strength was investigated for an ecological jute fiber reinforced polypropylene （JFRP）. High strength of JFRP is observed if jute fibers are well dispersed in the PP. It is necessary to pre-penetrate the matrix into the jute fiber bundle in producing the pellets for the dispersion of jute fibers, because the injection time should be reduced not to degrade the fiber strength at elevated temperature． For the pre-penetrating the matrix, Jute fibers should be twisted in opposite direction to the screw rotation at extruding the pellets. The interfacial failure is observed for any cases of the fiber lengths in pellet. However, the strength of JFRP has a maximum with respect to the fiber length. When the moderate fiber length encourages the ravels and dispersions of the fibers, high strength of the JFRP is obtained．A devised screw （CMH） is also effective for increasing thestrength of JFRP, because it improves fiber dispersion. If the JFRP absorbs moisture under high humidity, the strength of it decreases remarkably. The microscopic failure mode, however, is independent of the water absorption, i.e. interfacial failure is observed at all testing conditions. The reduction of fiber strength dominates that of JFRP due to water absorption. Key Words:Jute fiber, Polypropylene, JFRP, Fiber strength, Twisting direction, Pellet fiber length, Fiber dispersion, Resin penetration, CMH, Moisture absorption