Reinforcement and Toughening Mechanisms of Ionic Clusters in Ethylene-Propylene-Diene Monomer Rubber

Abstract

Zinc methacrylate (ZDMA) is widely used for reinforcing and toughening non-polar rubbers due to its ability to graft onto the rubber chains and form ionic clusters. However, the specific mechanisms by which these ionic clusters enhance the mechanical properties of rubbers remain to be fully elucidated. In this paper, the reinforcement and toughening effects of ZDMA in an ethylene-propylene-diene monomer (EPDM) rubber were systematically investigated. By adjusting the contents of ZDMA and bis(tert-butyldioxyisopropyl) benzene (BIPB), the tensile strength of ZDMA-modified EPDM vulcanizate at 20 °C increased from 21.70 MPa to 33.66 MPa, while the toughness improved from 24.29 MJ·m^-3 to 48.96 MJ·m^-3. The results demonstrated that the ionic cross-linking and strain amplification effects introduced by the ionic clusters were the primary causes for the significantly improved strength and toughness. Notably, it was found that the ionic cross-linking could be partially dissociated to promote homogeneous stress transfer and strain-induced crystallization (SIC) in the EPDM, which played a vital role in the rubber reinforcement and toughening. Overall, this study provides a comprehensive understanding of the reinforcement and toughening mechanism of ZDMA in EPDM, which is of great significance for the future research, development and application of reactive fillers in non-polar rubbers.