Polyhydroxybutyrate (PHB), a bio-derived and biodegradable polyester, has the potential to be a substitute for traditional polymers. PHB was modified with montmorillonite (MMT), a nanoclay, with the aim of improving its mechanical properties. The clay dispersion, mechanical, rheological and thermal properties of untreated and acid-treated MMT-modified PHB nanocomposites were investigated. Nanocomposite specimens at three different clay loading were prepared using extruder and injection moulding machine. Energy dispersive X-ray mapping revealed that nanocomposites with clay content of 3 phr exhibited better dispersion compared to nanocomposites with higher clay content. The mechanical properties of the MMT-modified PHB, such as the tensile and flexural modulus, were enhanced when compared to neat PHB. From rheology, PHB and PHB nanocomposites modified with untreated MMT exhibited Newtonian fluid behaviour in the tested frequency range. However, for nanocomposites modified with acid-treated MMT, shear thinning behaviour was observed at higher clay content. The nanocomposites also exhibited higher complex viscosity compared to PHB. From transmission electron microscopy analysis, exfoliation of the MMT was observed for the treated MMT nanocomposites at all clay loading. MMT-modified PHB has lower melting temperature when compared to neat PHB. Furthermore, it was found that the addition of MMT influenced the crystallisation behaviour of PHB. The presence of acid-treated MMT also reduced the degree of crystallinity with increasing clay content.

Oil palm empty fruit bunch (OPEFB) was heat treated at 180°C using a vacuum oven for one hour, extruded and compounded with high-density polyethylene at 10%, 20% and 30% weight fraction. The composites then were injection moulded into dumb-bell shaped specimens. The effect of composition and heat treatment on the thermal properties of composites were investigated using Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The tensile and flexural properties were also tested using an Instron Universal Testing Machine. TGA shows an increase in the degradation peak temperature of the heat-treated composites. DSC revealed an increasing trend in the degree of crystallinity (X c ) of the matrix as the heat-treated empty fruit bunch was used as a filler. An increment in the tensile modulus and tensile strain were observed for the treated fibre composites. In addition, the tensile strength value was increased for treated fibre composites with lower fibre loading.

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.