Abstract:
The twenty-first century has witnessed remarkable achievements in the rubber industry regarding
green technology through the development of natural fiber based rubber composites. A wide variety
of natural fibers extracted from coconut, palmyra and banana has been used as fillers in the
development of natural rubber (NR) based green composites, most importantly to reduce
environmental pollution caused by hazardous powdered fillers and to enhance reinforcement. Oil
palm fiber (OPF) is hard, tough and has the potential to reinforce the rubber matrix. Mesocarp part of
OPF, which generates as a waste material of palm oil processing mills was used as a filler in this
study. The objective was to investigate the effect of size of OPF on cure, physico-mechanical, water
absorption and ageing properties of NR composites. A chemical treatment was conducted to reduce
fiber size and to improve physico-mechanical properties. Chemical processing with sodium
hydroxide, bleaching with sodium chlorate and oxalic acid were conducted to remove residual oil and
reduce fiber size. A series of NR composites were prepared with 2 phr OPF by varying its size from
250 μm to below 50 μm. The NR composite prepared without OPF, but with 2 phr of carbon black
was considered as the control. Although an increase in properties was expected with the reduction of
fiber size, no significant increase was observed. Nevertheless, results showed the highest values for
the NR composite prepared with OPF in the size range 125-175 μm in regard to modulus at 300%
elongation, tensile strength, hardness, resilience and an average value for water absorption. This
revealed even dispersion of OPF in the rubber matrix of the above composite and the results were in
agreement with crosslink density indicated by the delta cure value. There was no decrease in tensile
modulus and strength after ageing, which indicates high retention of these properties. Overall, results
revealed that carbon black in NR composites could be replaced with OPF to manufacture rubber
products requiring hardness ranging from 29-36 Shore A.
Keywords: Oil palm fiber; Natural fillers; Natural rubber; Cure characteristics; Physico-mechanical
properties
