Effects of Epoxide Content and Blend Ratios on Properties of Dynamically Cured Epoxidized Natural Rubber/Poly(ether-block-amide) Copolymer Blends

Abstract

Abstract ENR with varying levels of epoxide groups ranging from 10 to 50 mol% was prepared in-house and later dynamically phenolic vulcanized by blending it with poly(ether-block-amide) copolymer (PEBA) at 160°C. The results revealed that the thermoplastic vulcanizates (TPVs) of ENR/PEBA blends exhibited a sea-island morphology. Increasing the epoxide content and PEBA proportion improved the strength properties, including higher Young's modulus (stiffness), toughness, tensile properties, and hardness. Additionally, increasing the epoxide content and ENR proportion in the TPVs resulted in decreased tension set values, indicating improved elastic properties. This is attributed to the interaction between the polar groups present in the phenolic-cured ENR domains and the PEBA molecules. This also caused a decrease in the size of the ENR domains dispersed in PEBA matrix as the content of epoxide groups increased. This effect, in turn, contributed to the enhancement of interfacial adhesion between the ENR domains and PEBA interfaces, leading to the observed improvements in the strength and elastic properties of the TPVs. Additionally, an increase in the epoxide content correlated with a decrease in Tan δ and tension set, further supporting the observed improvements in strength and elasticity. In addition, a single glass transition temperature (Tg) was observed in the ENR/PEBA blends, whereas two Tgs were observed in pure PEBA. The presence of a single Tg in the ENR/PEBA blend is attributed to the overlapping of the Tg of the ENR and PEBA immiscible blend components.