Characterization of High-Density Polyethylene (HDPE)-based Biocomposite with Green Seaweed Caulerpa lentillifera as Filler and Polyethylene-grafted-Maleic Anhydride (PE-g-MA) as Coupling Agent

Indonesia possesses abundant seaweed resources; however, their use in composites remains limited. This study investigates the impact of incorporating green seaweed (Caulerpa lentillifera) as a filler and polyethylene-grafted-maleic anhydride (PE-g-MA) as a coupling agent on the mechanical, thermal, morphological, water uptake, and soil degradation properties of high-density polyethylene (HDPE) biocomposite. C. lentillifera content in the biocomposite was varied from 10% to 40%, PE-g-MA content ranged from 0% to 15%, and C. lentillifera particle size was also varied. Results indicate that adding C. lentillifera significantly increases the biocomposite's modulus of elasticity (up to 1.63 GPa), thermal stability, and soil degradation resistance (up to 15%). The incorporation of PE-g-MA (up to 5%) effectively reduces water uptake to 0.94%, slightly improves mechanical properties, and enhances interfacial adhesion compared to the un-compatibilized biocomposite. A smaller C. lentillifera particle size further decreases water uptake and soil degradation, reaching 0.45% and 1.13%, respectively.