Processability and Physical Properties of Compatibilized Recycled HDPE/Rice Husk Biocomposites

The circular economy promotes plastic recycling, waste minimization, and sustainable materials. Hence, the use of agricultural waste and recycled plastics is an eco-friendly and economic outlook for developing eco-designed products. Moreover, new alternatives to reinforce recycled polyolefins and add value to agroindustrial byproducts are emerging to develop processable materials with reliable performance for industrial applications. In this study, post-consumer recycled high-density polyethylene (rHDPE) and ground rice husk (RH) of 20% w/w were blended in a torque rheometer with or without the following coupling agents: (i) maleic anhydride grafted polymer (MAEO) 5% w/w, (ii) neoalkoxy titanate (NAT) 1.5% w/w, and (iii) ethylene-glycidyl methacrylate copolymer (EGMA) 5% w/w. In terms of processability, the addition of RH decreased the specific energy consumption in the torque experiments with or without additives compared to neat rHDPE. Furthermore, the time to reach thermal stability in the extrusion process was improved with EGMA and MAEO compatibilizers. Tensile and impact test results showed that using coupling agents enhanced the properties of the RH composites. On the other hand, thermal properties analyzed through differential scanning calorimetry and thermogravimetric analysis showed no significant variation for all composites. The morphology of the tensile fracture surfaces was observed via scanning electron microscopy. The results show that these recycled composites are feasible for manufacturing products when an appropriate compatibilizer is used.