Preparation and characterization of poly(lactic acid)/rice hulls based biodegradable composites

Rice-hull-filled poly(lactic acid) (PLA) composites were prepared, with particular attention given to the enhancement of adhesion between polymer matrix and natural filler through addition of 5 wt.% PLA-grafted-MA (CA). Composites containing 20 and 30 wt.% rice hulls (RH), as well as composites where a certain amount of PLA matrix was substituted with a coupling agent, were investigated through tensile test and fracture test at low strain rate, using the concept of linear elastic fracture mechanics. Introduction of 20 wt.% rice hulls into PLA matrix resulted in increased tensile modulus and modulus in flexure, and decreased tensile strength and flexural strength. For PLA composite with 30 wt.% rice hulls, introduction of 5 wt.% CA caused 33% and 40% improvement, correspondingly in the composite tensile and flexural strength, obviously as a result of improved adhesion. Kc and Gc values were determined for PLA and PLA based composites, revealing that introduction of rice hulls into PLA decreases the material toughness. Thermal stability of PLA/RH composites was lower than thermal stability of neat PLA. The examination of PLA/rice-hull-based composites revealed that rice-hull agricultural waste could be used as a biodegradable eco-friendly filler, rather to minimize environmental pollution and cost of the final product than as a reinforcement of PLA matrix.