COMPARATIVE STUDIES ON CURE CHARACTERISTICS AND MECHANICAL PROPERTIES OF OIL PALM BIOMASS FILLED NATURAL RUBBER COMPOSITES

Abstract

Oil palm is categorised as the most important agricultural crop in Malaysia occupying about 70% of the agricultural land. The palm oil industry is one of the biggest contributors to Malaysia’s Gross National Income (GNI). However, the rapid development of the palm oil industry causes high production of palm oil waste which is a worrying environmental issue these days. As the need to promote sustainable, renewable and clean energy keeps rising, researchers have taken a keen interest in utilising palm oil waste as a source of biomass. Palm oil waste such as palm kernel shell (PKS) is a great source of valuable biomass and readily available in large amounts which can then be transformed into biochar and activated carbon via pyrolysis and activation processes, respectively. By producing palm kernel shell biochar (PKSB) and activated palm kernel shell (APKS) derived from palm oil waste, they can potentially be used as potential bio-fillers in rubber composites. The research aimed to study the effect of different loading of PKSB and APKS in natural rubber (NR) composite since they have higher carbon content, porosity and surface area compared to other biomass fillers. The surface morphology analysis by scanning electron microscopy, cure characteristics, swelling measurements, and mechanical properties was analysed. APKS was observed to have well-developed pores that could provide a high surface area of contact resulting in improved mechanical interlocking between filler and rubber matrix. Comparisons were made between PKSB, APKS and other bio-fillers such as coconut fibre (CF), bamboo charcoal (BC) and untreated kenaf (UK). The cure characteristics for PKSB showed a high range of maximum torque (MH) values (11-23 dN.m), better in ts2 (1 min) and t90 (2-3 min), whereas the MH values for APKS were slightly lower and longer in t90 which were 14-15 dN.m and 2-4 min, respectively. PKSB also showed a better swelling percentage (226%-329%) which would indicate high crosslink density compared to APKS (305%-336%). Moreover, APKS showed better tensile strength (8-18 MPa) and elongation at break (519%-669%) as the filler loading increased in comparison with PKSB which recorded a tensile strength of 5-14 MPa and elongation at break of 385%-561%. Based on the results, it can be concluded that the optimum value of APKS filler loading ratio in NR composite is 40 phr as 40 phr of APKS filled NR composite had the highest mechanical properties compared to the other filler loading ratios. Both PKSB and APKS have great potential to be used and commercialised as semi-reinforcing fillers in the rubber industry. This way, PSKB and APKS are able to provide a sustainable alternative to existing petroleum-based fillers and could help to reduce the abundance of palm oil waste while producing high-performance rubber-based products.