Enhancing supercritical CO2 immersion resistance of aramid pulp-filled ethylene propylene diene monomer rubber composites through reinforced interfacial bonding

• A method to treat the aramid fiber surface, which can increase the aramid-rubber H-pull-out force by ∼300 %, is proposed. • Strengthening the interfacial bonding between aramid fibers and rubber enhances the composite’s resistance to CO 2 gas explosion. • Aramid pulp-filled ethylene propylene diene monomer rubber composite with excellent supercritical CO 2 immersion resistance is designed. The development of supercritical carbon dioxide(sCO 2 )-resistant sealing rubbers is a key solution to addressing the critical challenges in the application of sCO 2 -related industries. This study focused on enhancing the sCO 2 immersion resistance of aramid fiber-reinforced ethylene propylene diene monomer (EPDM) rubber composites through strengthened interfacial bonding. Combined modification with coupling agents and polyisocyanate was applied to the surfaces of phosphoric acid-etched aramid fibers. H pull-out tests revealed that after modification, the interfacial bonding strength between the fibers and rubber significantly increased from 12.9 to 51.1 N. Scanning electron microscopy analysis further confirmed this enhanced interfacial bonding. Notably, the modified interface had minimal impact on the high-temperature compression set, thermal aging resistance, thermal decomposition temperature, or low-temperature performance. However, sCO 2 immersion tests (165 °C, 17 MPa, 3 days) revealed that interface reinforcement improved the tensile strength retention of EPDM composites containing phosphoric acid-treated aramid fibers modified with coupling agents and polyisocyanate. Specifically, this modification reduced tensile strength loss from 41 % to 33 %. This study provides a simple and effective surface impregnation-based interfacial reinforcement strategy to enhance the sCO 2 resistance of rubber composites.