Compatibilisation of Silica-filled Natural Rubber Compounds by Functionalized Low Molecular Weight Polymer

In silica-filled natural rubber, it is essential to use coupling agents or compatibilisers to enhance filler-rubber interactions, reduce silica network formation and hence to obtain good reinforcement. This work investigates the effect of epoxidised low molecular weight natural rubber (ELMWNR) in silica-filled NR compounds on processing, mechanical, dynamic-mechanical and morphological properties. ELMWNRs with 12 and 28 mol% epoxide groups having a molecular weight in the range of 50,000-60,000 g/mol were added into the compounds as compatibilisers at varying loadings from 0-15 phr. The reference compound containing bis-(triethoxysilylpropyl) tetrasulfide (TESPT) as coupling agent was also prepared for comparison. The addition of 10 phr ELMWNR-28 in the silica-filled NR compounds not only decreases mixing torque, compound viscosity and Payne effect to the levels close to those of the compound with TESPT, but also increases bound rubber content and filler dispersion resulting in improvement of mechanical properties. However, the TESPT-silica system still provides better mechanical and dynamic mechanical properties compared to the alternative ELMWNR-silica systems. Overall, ELMWNR can be an alternative as natural-based compatibiliser with no ethanol emission like in the case with TESPT