Conditioning effect on the mechanical and thermal properties of heat-treated oil palm empty fruit bunch/high-density polyethylene composite

Oil palm empty fruit bunch (EFB) is one of the potential natural fibre that can be used as an alternative to synthetic fibre. EFB was heat-treated at 180°C using vacuum oven for 1 h, extrusion compounded with high-density polyethylene at 10%, 20% and 30% weight fraction. The composites were injection moulded into dumb-bell (ASTM D-638) and bar-shaped specimens (ASTM E-23). The composites were exposed to different environments which are soil burial and indoor environment for 3 months. The effects of conditioning on mechanical and thermal properties were studied relative to the dry as moulded samples as a standard. It was found that the mechanical and thermal properties of composites under soil burial conditions were reduced. Tensile modulus of 30% untreated fibre loading reduced from 1.56 GPa for dry to 1.03 GPa for soil burial conditions, respectively. The same reduction was also found in the flexural modulus. However, the value of treated fibre composites was found slightly higher compared to untreated fibre composites. The treated fibre composites showed more resistance towards the environment condition. Composites made from heat-treated EFB show improved thermal stability, expected due to better compatibility between fibres and matrices, thus lowering the moisture intake, despite the conditions of the samples. However, indoor exposure has no significant effect on the thermal and mechanical properties of composites.