Exploring the thermomechanical properties of peroxide/co‐agent assisted thermoplastic vulcanizates through temperature scanning stress relaxation measurements

Abstract

AbstractTemperature scanning stress relaxation (TSSR) measurement of peroxide vulcanized polymer blends of polypropylene (PP) and ultrahigh molecular‐EPDM (UHM‐EPDM) rubber has been performed to study the thermomechanical behavior of thermoplastic vulcanizates (TPVs). Co‐agents play crucial roles in the enhancement of properties of TPVs. Different types of co‐agents (Triallyl cyanurate‐TAC; N, N‐m‐phenylene‐dimaleimide‐HVA2; zinc dimethacrylate‐ZDMA; and in‐situ formed zinc dimethacrylate‐ZMA) have been explored in this work. TSSR study shows that higher T50 and T90 values have been achieved in ZMA co‐agent assisted‐TPV. Higher TSSR‐index (RI) value was also found for the same co‐agent ZMA, indicating higher elastic behavior. TSSR result supports the mechanical and rheological properties, and it is found that the ZMA and ZDMA show higher mechanical strength. Cross‐linked‐density calculated by modified Flory–Rehner equation and the cross‐link‐density as obtained from TSSR method have been compared and the trend was found to be the same. Stress relaxation study shows the slow relaxation‐phenomena of the ZMA‐TPV with slowest relaxation‐time (θr) than the other TPVs, which correlates with superior material strength. Thermogravimetric analysis proves that there is a difference in degradation temperature of the blends at approximately 5–10°C. Ultrahigh molecular weight‐EPDM/PP based TPVs reveal superior thermomechanical and physico‐mechanical properties with ZMA and ZDMA co‐agent over TAC and HVA2. These ultrahigh molecular weight‐EPDM based TPVs can be used in automotive seals/strips, hoses, bellows, and 2 K‐molds for automotive applications.