Utilization of Indonesian seaweed in polyethylene-based composite with coconut husk powder as bio-compatibilizer

The addition bio-based materials into plastic is expected to produce composites that can be decompose in a shorter time compared to petroleum-based plastics. Combining hydrophobic-high density polyethylene (HDPE), with a hydrophilic-biobased material, is challenging and requires a compatibilizer agent to produce good performance bio-composite. In this study, Halymenia sp. or Gracilaria sp. seaweed was utilized as filler in HDPE based composite by 20% of total weight, and coconut husk powder that varied at 0%, 1%, 5%, and 10% was used as bio-compatibilizer. The materials were mixed in the rheomixer (rotor rotating speed of 80 rpm, at 140 °C for 5 min). The addition of 1% coconut husk powder can improve the modulus of elasticity of HDPE-Halymenia extract and HDPE-Gracilaria residue by 21.43% and 55.71%, respectively, compare to pure HDPE. Furthermore, the crystallinity index of Halymenia extract with the addition of 1% coconut husk powder was the highest (50.40%) among other HDPE-Halymenia extract composites in this study.