Silica-reinforced natural rubber with epoxidized low molecular weight rubber as a compatibilizer

This work investigates the effect of epoxidized low molecular weight natural rubber (ELMWNR) in silica-filled NR compounds on processing, mechanical and dynamic mechanical properties. The ELMWNRs with mol% epoxide groups varying from 0-50 and molecular weight in a range of 50,000-60,000 g/mol were prepared from depolymerization of epoxidized natural rubber using periodic acid in latex state. They were then added in the silica-filled NR compounds as a compatibilizer at varying loading from 0-15 phr. The addition of ELMWNR decreases compound viscosity and Payne effect, i.e. filler-filler interaction. The optimal mechanical properties of silica-filled vulcanizates are observed at the ELMWNR-28 (28 mol% epoxide) loading of 10 phr. The incorporation of ELMWNR with 28 and 51 mol% epoxide groups into NR compounds introduces a second glass transition temperature and affects on their dynamic mechanical properties. Higher epoxide content leads to higher Tan δ of the rubber vulcanizates in the range of normal service temperature.