Green surface modification strategy: Synergistic carboxymethyl cellulose -SiO2 hybrid layer boosts interfacial and ablative properties of aramid fiber/EPDM composites

In this study, a hybrid interfacial phase was constructed between aramid fibers (AFs) and ethylene-propylene-diene monomer (EPDM) using carboxymethyl cellulose (CMC) and silicon dioxide (SiO 2 ), two environmentally-friendly materials. Specifically, CMC self-assembled into a folded interfacial layer through hydrogen bonding with hydroxyl groups on AF surfaces, while SiO 2 nanoparticles were subsequently adsorbed to generate nanoscale roughness. Low-field NMR and AFM analyses revealed that this synergistic modification significantly enhanced fiber-matrix infiltration, forming mechanical interlocking via hydrogen bonds and topological entanglement. Consequently, the tensile strength of both AFs/EPDM composites (F1414 and F12) was increased by more than 20 %. In situ SEM observations further elucidated the positive correlation between interfacial reinforcement and mechanical performance. Moreover, comparative studies on two AF types (F1414 and F12) indicated that the Si-rich interfacial layer not only improved carbonization density but also enhanced ablation resistance (mass loss reduced by 28 %) and thermal insulation (back temperature reduced by 22.4 °C). This facile and environmentally benign strategy provides a scalable approach for fabricating high-performance composites using sustainable materials.