Blending of NR/BR/ENR/EPDM-g-GMA by reactive processing for tire sidewall applications

Application of ethylene–propylene-diene monomer (EPDM) grafted with glycidyl methacrylate (GMA), along with epoxidized natural rubber (ENR) was investigated for tire sidewall blend. The presence of ENR and EPDM-g-GMA improved physico-mechanical properties of the blends. The best results were obtained using 5 phr EPDM-g-GMA in the blend. Tensile and tear strength of the blend with 5 phr EPDM-g-GMA were 13.7% and 46.5% higher than conventional blend of tire sidewall, respectively. Ozone resistance in dynamic condition of NR/BR/ENR with 5 phr EPDM-g-GMA were 20% and 30% superior than NR/butadiene rubber (BR)/ENR/EPDM and conventional NR/BR with N-(1,3-dimethylbutyl)- N′-phenyl- p-phenylene, respectively. Improved mechanical and ozone resistance properties are due to better homogeneity of cross-link density and carbon black distribution in the blend.