Utilization of palm oil as an alternative processing oil in carbon black-filled natural rubber compounds

Abstract

Due to the toxicity of distillate aromatic extract (DAE), palm oil (PO) being environmental friendliness, renewability, and sustainability, was used as an alternative processing oil in this study. The properties of carbon black-filled natural rubber compounds containing PO were investigated and compared with the DAE-added rubber compound. The results revealed that the presence of PO in the rubber compound gave the same degree of filler–filler interactions but higher filler-rubber interactions compared with the one with DAE. Payne effect as referred to filler-filler interactions of the rubber compounds with DAE and PO was 191 and 189 kPa, respectively. In addition, the presence of PO not only accelerated the vulcanization reaction but also reduced the crosslink density within the rubber matrix. The crosslinking type of PO-added rubber compounds consisted only of polysulfidic linkages, whereas the DAE-added rubber compound contained various crosslinking types, i.e., mono-, di-, and polysulfidic linkages. On the other hand, the presence of PO in rubber compounds promoted a positive effect on elastic properties, as indicated by the temperature scanning stress relaxation (TSSR) index and tan δ at 60 °C. The TSSR index of rubber compounds with DAE and PO was 0.69 and 0.71, respectively. Given the low tan δ at 60 °C of the PO-added rubber compounds, PO promoted a low rolling resistance when applied in tire applications, providing tires with safe energy.