High mechanical interlocking and hydrogen bonding based carboxymethyl cellulose/SiO2 composite structures for interfacial bonding of reinforced polyimide fiber/EPDM composites

In this study, carboxymethyl cellulose (CMC), a polymer abundant in hydroxyl and carboxyl groups, was employed as an interfacial layer between polyimide fibers and EPDM rubber. The formation of hydrogen bonds between CMC and the polyimide fibers facilitated a robust encapsulation of CMC on the fiber surface. Additionally, a greater number of SiO 2 nanoparticles were adsorbed onto the CMC surface through hydrogen bonding and condensation reactions, significantly enhancing the fiber's surface roughness and the matrix's wettability. This strong mechanical interlocking structure markedly improved the interfacial adhesion and mechanical properties of the composites. Specifically, the H pull-out force, tensile strength, and elongation at break increased by 84.8 %, 89 %, and 45 %, respectively, compared to the control samples. In-situ electron microscopy further confirmed that the reinforced interface effectively inhibited crack propagation along the interface. Low-field NMR analysis revealed that the enhanced interfacial bonding restricted the mobility of rubber molecules, contributing to higher strains and stresses during the orientation hardening phase under tension. Moreover, the improved interfacial adhesion and the incorporation of SiO 2 within the interfacial layer also enhanced the ablative resistance and thermal insulation properties. These findings demonstrate that the CMC/SiO 2 encapsulation strategy represents an environmentally friendly, rapid, and efficient interfacial modification method for polyimide fiber-reinforced EPDM insulation materials.