Investigation on the application of coconut copra residue for the reinforcement of high-density polyethylene composites

In the food industry, a significant amount of coconut meat residue is discarded annually following milk extraction. This waste has traditionally been considered low value and underutilized. Our research aimed to investigate the potential of utilizing this by-product as a reinforcement material in fiber-reinforced polymer composites. We examined the morphology and mechanical properties of composites produced from a mixture of high-density polyethylene (HDPE) powder and coconut flour, with varying concentrations ranging from 10 to 40 wt%. The materials were processed using a twin-screw roller at 160 °C for 15 min and then molded into 20 × 20 cm2 squares. The composite samples were subjected to testing for tensile, flexural, and impact strength using a standard material testing machine in a controlled setting. Our results showed that as the proportion of coconut flour in the formulations increased, the density decreased while water absorption increased. Moreover, the impact strength of the composites improved with higher fiber content, although the tensile and flexural properties decreased. Scanning electron microscopy (SEM) images indicated that while the fibers were not well aligned in the matrix, there were no visible gaps between the fibers and HDPE matrix, and no significant cavities due to particle pullout, suggesting strong interface bonding. Additionally, we examined how temperature and duration impact coconut meat, akin to the composite formation process, using Fourier transform infrared spectroscopy (FTIR). Our findings revealed notable alterations in coconut meat due to fiber degradation. Ultimately, we demonstrated the feasibility of incorporating coconut meat-filled HDPE composites for indoor furniture manufacturing.