Comparison of thermo-oxidative ageing and thermal analysis of carbon black-filled NR/Virgin EPDM and NR/Recycled EPDM blends

Blends of natural rubber/virgin ethylene propylene diene monomer (NR/Virgin EPDM) and natural rubber/recycled ethylene propylene diene monomer (NR/Recycled EPDM) were prepared on a two-roll mill. A fixed amount of carbon black at 30 parts per hundred rubbers (phr) was also incorporated. Three different thermal studies, namely thermo-oxidative ageing, thermogravimetric analysis and dynamic mechanical analysis, were carried out and compared. Thermal ageing and thermogravimetric analysis of the blends containing high weight ratio of virgin or recycled EPDM suggested higher thermal stability of the blends by showing higher retained tensile properties as well as shifting initiation of degradation to a higher temperature. Due to the fact that recycled EPDM consists of crosslinking precursor, greater crosslink density was observed when recycled EPDM content was increased. This could be verified from the augmentation of storage modulus (E′) as well as the reduction in damping factor (tan δmax) when the weight ratio of recycled EPDM was increased.