Efficient toughening of epoxy anhydride thermosets with modified PVA fibers

The poor interfacial properties of polyvinyl alcohol (PVA) fibers and epoxy resin seriously affect the toughening effect of PVA fibers on epoxy resin. To solve this problem, the surface of PVA fibers was modified with 3-aminopropyltriethoxysilane (KH550) and 3-glycidoxypropyltrimethoxysilane (KH560), as well as the surface of PVA fibers with tannic acid (TA) and KH560. The acid-cured epoxy resin toughening mechanism of the modified PVA fibers was systematically investigated by multiscale analysis. The experimental data showed that the epoxy resin performed best when TA and KH560 synergistically modified PVA fibers. The impact strength of the epoxy resin increased by 76.3% and the tensile strength by 20.3%. The toughening mechanism of modified PVA fibers on the epoxy resin was revealed by a series of characterizations such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA). Because KH560 can participate in the curing reaction of the epoxy resin, it greatly enhances the adhesion between the fiber and the resin. The toughening mechanism of TA and KH560 working together on PVA fibers to strengthen epoxy resin is summarized through the analysis of different scales. This also offers theoretical and experimental support for using PVA fibers in composites.