Construction of high-barrier, high-strength EPDM composites: Synergistic optimization of zinc methacrylate -induced covalent-ionic dual network and hydroxy terminated polybutadiene plasticization

High-barrier rubber sealing materials are the most widely used sealing components in high-pressure hydrogen storage systems. The gas permeation behavior of rubber materials in high-pressure hydrogen environments is critical to ensuring the long-term sealing reliability and safety of such systems. This study incorporated butyl methacrylate (BMA), methacrylamide (MAM), and zinc methacrylate (ZDMA) into an ethylene propylene diene monomer (EPDM) matrix, establishing covalent crosslinking, grafted covalent integral, covalent-hydrogen bond dual crosslinking, and covalent-ionic dual crosslinking network systems within the EPDM. Among these, the covalent-ionic dual crosslinking network demonstrated the most significant effect, enhancing the composite's hydrogen barrier performance and tensile strength by 22.9% and 227.4%, respectively. The study revealed that microporous defects formed in the matrix when the ZDMA content reached 20 phr. Further investigations revealed that introducing 20 phr hydroxyl-terminated polybutadiene (HTPB) as a plasticizer eliminated these defects by im-proving ZDMA dispersion, further enhancing hydrogen barrier performance and tensile strength to 31.8% and 316.7%, respectively. This study provides a key methodology for optimizing the performance of high-pressure hydrogen sealing materials.