Thermo-Oxidative Aging and Performance Comparison of Recovered, Sustainable, and Virgin Carbon Black in Ethylene Propylene Diene Monomer-Based Elastomers

Pyrolysis is becoming increasingly important in the context of recycling and the volume of end-of-life tires worldwide. Sustainable carbon black (sCB), which is produced from pyrolysis oil instead of crude oil, and recovered carbon black (rCB), which is the remaining solid from pyrolysis, are promising secondary raw materials for rubber compounds as a substitute for industrial carbon black produced from fossil resources. This study investigates the possibility of substituting carbon black N550 partially or fully in an EPDM (Ethylene Propylene Diene Monomer) sealing compound. rCB contains impurities that affect the properties of the compound. Aging at higher temperatures, in the presence of oxygen is studied. The properties of the compounds are evaluated after heat treatment in air at different temperatures for up to 6 weeks. The results show that sCB is very close to N550 as a raw material and in terms of its in-rubber properties. Due to the impurities, rCB alters the cross-linking density and structure of the polymer-sulfur network (shift to polysulfidic structure). Lower reinforcement is also observed, which is related to weaker polymer-filler (decrease of I_3/1 for sCB by 3% and rCB by 43% related to vCB) and filler-filler interactions. Aging effects are also more pronounced in the compounds containing rCB.