Influence of polyamide acid coating reaction on the properties of aramid fibre

The interfacial properties of aramid fibres (AFs) affect their mechanical behaviours. In this work, polyamide acid (PAA) was grafted onto the surface of aramid fibres (AF@PAA) to reinforce epoxy resin (EP E44) by improving the interfacial properties. The AF@PAA contained many active groups and improved the roughness of aramid fibres on the surface, which improved the interfacial performance and mechanical properties of AF-reinforced E44 composites. FTIR and XPS showed the introduction of C-O and -COO-, which confirmed the existence of chemical reactions among groups between the aramid fibres and polyamide acid. A micro-droplet test proved that the benzene ring of the AF could be oxidized under high temperature, and the oxygen-containing groups generated during the oxidation process were important for the grafting process of polyamide acid. The interfacial shear strength (IFSS) increased by 40.7% after treatment with 5 wt% polyamide acid. This study provides a feasible method for interfacial modification in AF-reinforced epoxy resin composites and may be applicable to rubber composite systems.