Enhanced mechanical properties of aramid fiber/epoxy composites through reinforcing interfacial adhesion based on strong hydrogen bonding interactions

Aramid fiber/epoxy (AF/EP) composites often exhibit suboptimal interfacial bonding between the fibers and matrix, which undermines their mechanical performance and hinders the broader application of these materials. Herein, an amphiphilic polymer brush of polyvinyl alcohol-2-Amino-4-hydroxy-6-methylpyrimidine-hexylisocyanate (PVA-UPy) as interfacial modification agent was designed and synthesized to reinforce interfacial bonding of AF/EP composites. The incorporation of PVA-UPy markedly improved the interfacial adhesion between the aramid fibers and the epoxy matrix, leveraging strong supramolecular interactions and principle of "like dissolves like". The interfacial shear strength of AF/EP composites displayed a substantial boost from 27.9 MPa to 60.9 MPa. Additionally, the interlaminar shear strength, flexural strength and tensile strength of composites were reinforced by 55.9 %, 46.8 % and 42.9 %, respectively. The reinforcement is ascribed to the formation of strong hydrogen bonds between 2-Amino-4-hydroxy-6-methylpyrimidine (UPy) side chain of PVA-UPy and the AF/EP interface, as well as the compatibility principle between hydroxyl and epoxy. This work presents a novel and straightforward approach to the design and synthesis of interfacial modification agents, offering an effective strategy for reinforcing interfacial bonding in composites through supramolecular interactions.