Mechanical properties of bio-fibers-reinforced high-density polyethylene composites: effect of coupling agents and bio-fillers

Bio-based fibers (wood and bamboo)-filled high-density polyethylene composites were prepared in a twin-screw extruder using two types of coupling agents: maleated polyethylene and glycidyl methacrylate-grafted polyethylene. The effect of bio-fibers used as filler on the mechanical properties of composites was studied. It was observed that mechanical properties such as tensile and flexural strengths of the composites with coupling agent increased with increasing filler loadings. Tensile strength and flexural strength exhibited improvement up to 66% and 90%, respectively, over virgin high-density polyethylene. The maximum enhancement in the properties was observed with wood pulp when compared with wood- or bamboo flour-filled composites. Effect of coupling agents on the performance of composites was evaluated at 30% filler loading with wood flour as the filler. The study suggested that glycidyl methacrylate-grafted polyethylene exhibited better tensile and flexural properties as compared with maleated polyethylene. Impact strength of the composites prepared with coupling agent was found to be more than uncoupled composites. Among the fiber type, the impact strength of wood-fiber-filled composites was superior than that of bamboo flour-filled composites. Moisture absorption study indicated that even at 40% filler loading, moisture gain by the wood fiber- and bamboo flour-filled composites was merely 1.55% and 2.60% after 600 h of water immersion test, which suggests encapsulation of filler material by the polymer matrix.