Thermoplastic vulcanizates based on epoxidized natural rubber/polypropylene blends: Selection of optimal peroxide type and concentration in relation to mixing conditions

A proper balance between degree crosslinking of ENR and degradation of PP-phase, and the tendency of peroxide to form smelly by-products, in particular acetophenone are investigated on a 60/40 ENR/PP TPV. Four types of peroxides were used at two mixing temperatures: 160 and 180 oC. The maximum and final mixing torques are clearly related to the intrinsic decomposition temperature of the particular peroxide used, where DCP and DTBPIB turn out to be effective at 160 °C, whereas the other two type of peroxides require a higher temperature of 180 °C. The best mechanical properties are obtained at lower mixing temperature with DCP and DTBPIB, presumably due to less degradation of the PP and ENR. Unfortunately, these two types of peroxides form more smelly by-products and blooming than those of the DTBPHY and DTBPH. Dependent on the requirements of the pertinent application, a balanced selection needs to be made between the various factors involved to obtain an optimal product performance of these ENR/PP TPVs.