Effect of oil palm fibre and pineapple leaves fibre on biodegradability, tensile and water absorption properties of polylactic acid based fibre composite / Norsuriati Muhmad Hapizi

Fabrication and analysis of polymer composites from Polylactic Acid (PLA) on two types of fibre, oil palm fibre (OPF) and pineapple leaf fibre (PALF), with three different percentages of fibre loading were investigated in this work. In this study, the effect of biodegradable PLA with the incorporation of these fibres on tensile, biodegradability, water absorption, thermal, and morphological analysis was performed. Initially, different OPF and PALF fibre compositions of 10%, 50%, and 60% with PLA were compounded using a Haake twin screw compounder. In addition, a hybrid composition containing 40% starch, 10% PLA, OPF, and PALF fibre 50% was tested. The tensile properties test shows that increasing the fibre loading will reduce the tensile strength of the composites. The highest tensile strength value (17MPa) was found for OPF with a composition of 10% compared to other composites. Soil burial testing for three months and water absorption testing for one month at RT and 50℃ were used to assess the biodegradability of the OPF and PALF composites. The degradability of composites was observed to increase with high fibre loading due to the enzymatic attack of microorganisms on the composites. The composite PLA50/OPF50/Lubricant (PLAOPF50L) shows a high degradation rate at moderate tensile strength (7MPa) and lost tensile properties within two months. For PALF composites, the degradation rate is fastest for 60% fibre loading within one month, with a strength of 5.5 MPa. For highest filled fibre loading, these composites also possessed a high water absorption rate. Based on this result, PLA50/OPF50/L has better result as compared to PLA50/PALF50/L. This is due to OPF composite has sufficient tensile properties for straw making and consider as faster degradation rate. From the FTIR spectrum displayed after three months of soil burial, the intensity of the peak significantly decreased and broadened at peak 3426cmˉ¹ due to the OH group as a result of degradation. Morphological analysis of OPF and PALF composites was carried out using SEM, showing that after three months of soil burial, many voids and cracks took place as higher fibre loading was used. The OPF composites are recognised to be the recommended composites since they provide better tensile properties and similar fast degradation as PALF composites. The optimum fibre content was found to be 50% (PLAOPF50L), which dropped in mechanical properties, showing high degradability. The high fibre loading fibres conferred easy biodegradability for composite applications. Higher immersion temperature (50℃) seems to accelerate the moisture uptake behaviour at maximum 18% compared to RT (10%). After 1 month of immersion at 50℃ increased less than double than RT. This may be attributed to different diffusivity of water into the composites, leading to interfacial cracks induced by moisture at an accelerated rate due to the degradation in the fibre-matrix interface region and the presence of water molecules in the OPF and PALF composites. Hence, composite PLAOPF50L is a useful formulation for biodegradable straw applications.