Effect of Modified Polyurethane Sizing Agent on Interfacial Properties of Aramid Fiber

ABSTRACT Waterborne polyurethane ( WPU ) modified by titanium dioxide ( TiO 2 ), which was treated by γ‐methacryloxypropyltrimethoxysilane (KH570), was used to coat the aramid fiber ( AF ), improving the interfacial bonding with AF and thermoplastic polyurethane elastomer ( TPU ). The effects of KH570 ‐modified TiO 2 on the surface characteristics of AF , interfacial bonding, and the mechanical properties of the AF and TPU composites were investigated. The results of Fourier‐transform infrared ( FTIR ) spectroscopy, x‐ray photoelectron spectroscopy ( XPS ), and scanning electron microscopy ( SEM ) showed that the TiO 2 was grafted by KH570 and better dispersed on the AF surface. When the content of KH570 was 2 wt%, TiO 2 can be uniformly distributed on the AF surface, and the tensile strength of the fiber was significantly increased by 28.76% compared with that of the AF only coated with the WPU sizing agent. The improvement of fiber wettability was confirmed by water contact angle and surface energy measurements. The tensile strength, interlaminar shear strength, and flexural strength of the composites with fiber treated by adding KH570 ‐modified TiO 2 to WPU were increased by 19.37%, 104.48%, and 47.94% more than the composites with untreated AF , respectively, and 4.11%, 20.23%, and 13.93% more than the composites where the AF was treated by adding unmodified TiO 2 to WPU . The improved dispersion and strengthened interfacial bonding imparted by the KH570 modification of TiO 2 are identified as the primary factors contributing to the enhanced performance of the composite.