POSS-bound ZnO nanowires as interphase for enhancing interfacial strength and hydrothermal aging resistance of PBO fiber/epoxy resin composites

A new hierarchical reinforcement was fabricated by growing ZnO nanowires (NWs) onto poly(p-phenylene benzobisoxazole) (PBO) fibers using a mild hydrothermal method, which served as a platform for the polyhedral oligomeric silsesquioxanes (POSS) grafting, using 3-aminopropyltrimethoxysilane (APTMS) as a bridging agent. Scanning electron microscopy (SEM) was employed to characterize the surface morphologies of PBO fibers and the de-bonding surface morphologies of their composites. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the chemical bonding nature between ZnO NWs and APTMS, as well as between APTMS and POSS. The reinforcement offered a 83.4% enhancement in the interfacial shear strength (IFSS) without degrading the base fiber. Moreover, the possible interfacial property enhancing reasons were explored. The hydrothermal aging resistance of PBO/epoxy composites was also greatly improved.