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

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