Substitution of Aromatic Oil with Palm Oil in Natural Rubber/Silica Composites via Latex Processing

Rubber materials incorporating vegetable oils are being developed as sustainable alternatives to conventional petroleum-derived plasticizers. In this study, palm oil (PO) was used as a green processing oil for natural rubber (NR) composites, and aromatic oil (AO) was included for comparative analysis. The preparation of rubber material via the latex method, with and without vulcanizing agents, was also compared to the conventional preparation method. The test results showed that replacing AO with PO in the latex method yielded a similar cure rate index. The Payne effect, indicating the extent of filler-rubber interaction via the latex method, was 182 kPa for AO and 171 kPa for PO. The mechanical properties in terms of the Young's modulus of the PO-based composites were higher than those of the AO-based counterparts. Furthermore, the PO-based composites exhibited the smallest tan δ value at 60 °C (0.05), indicating the lowest rolling resistance. Life cycle assessment results showed that the PO-based natural rubber latex reduces fossil fuel depletion, human toxicity, and ozone layer depletion. Moreover, the latex method reduces human toxicity compared to the conventional method. Substituting PO in place of AO in rubber compounds serves as a suitable alternative plasticizer for rubber products.