Improvement of mechanical properties of long jute fiber reinforced polylactide prepared by injection molding process

Natural plant fibers have recently been attracting attention as reinforcement for plastics due to their high specific mechanical properties and carbon neutrality. This study investigated the preparation process of long jute fibers reinforced polylactide acid (LJF/PLA) pellets by injection molding and explored the improvement of mechanical properties of molded LJF/PLA composites in relation to preservation of molecular weights of PLA matrix. LJF/PLA pellets containing 50mass% of jute fibers were prepared by an original pultrusion process developed for manufacturing long fiber reinforced thermoplastics (LFT), with excellent impregnation of resin into jute fiber bundles. Evaluation of injection-molded specimens from LJF/PLA pellets revealed that their tensile and flexural strength were dependent on molecular weights of PLA matrix, which correspondingly decreased with the moisture content of the original LJF/PLA pellets by the hydrolysis reaction. In the evaluation of chopped jute fiber reinforced PLA (Chopped-JF/PLA), prepared by the ordinary extruding method and injection molding, it was revealed that severe dehydration of jute fibers prior to compounding was proven to be effective for preventing the deterioration in the molecular weight of PLA, and that better fiber dispersion in ChoppedJF/PLA than in LJF/PLA contributed to attaining high mechanical properties in spite of shorter average fiber length remaining in the composites.