Evaluation of suitability of sesame oil as an alternative for aromatic processing oil in natural rubber composites

Abstract

Polycyclic aromatic oils, high in aromatic content are used in tyre compounds as processing aids and these have been found to be carcinogenic. Therefore, it is necessary to find processing aids consisting of a low content of aromatics which would help to overcome the problem associated with the use of petroleum-based aromatic oils. The main aim of this research was to develop carbon black filled natural rubber (NR) composites using environmentally friendly sesame oil as the processing aid. Initially sesame oil was characterized using Fourier Transform Infra-Red analysis. Thereafter, a series of NR based tyre tread compounds was prepared by varying the sesame oil loading from 3-9 phr at 2 phr intervals. Cure characteristics, physico-mechanical and swelling properties of these composites were evaluated and compared with those of the composite prepared with the aromatic processing oil, Dutrex-R (control). Dispersibility of carbon black in all the NR composites was assessed. Viscosity, processing safety and cure rate of the composite produced with 5 phr sesame oil were higher compared to the control and indicated that the oil behaves as a co-activator in rubber compounds. Hardness, modulus at 100% elongation and abrasion volume loss of the vulcanizates prepared with more than 5 phr sesame oil were lower, whereas tensile strength, elongation at break and resilience were higher than those of the control. Tear strength and compression set of the vulcanizates prepared with 5 phr sesame oil were comparable to those of the control. Further, the former vulcanizate showed a higher and lower swelling indices in toluene and water, respectively compared to the control. Furthermore, the vulcanizates prepared with sesame oil showed better ageing resistance in comparison to the control. Hence, sesame oil could be a suitable alternative for Dutrex-R in tyre tread compounds at 5 phr level.