Improving aramid pulp dispersion in epoxy resin via the in situ preparation of SiO2 on an aramid pulp surface

Aramid pulp (AP) is a highly fibrillated form of fiber? with excellent heat resistance, wear resistance, size stability, and other beneficial properties, that can be dispersed in rubber or resin matrix systems. Its fibrillation results in a large surface area. However, AP easily tangles and aggregates between fibers because of its large surface area. Consequently, it experiences difficulty in dispersing in matrices, especially when a relatively large amount of pulp is needed to be mixed. In this study, a SiO2 nanoparticle was synthesized on the surface of AP through the hydrolysis of tetraethyl orthosilicate to improve the dispersion of AP in an epoxy matrix. Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, and scanning electron microscopy showed that SiO2 nanoparticles coated on the pulp could improve the thermal and mechanical properties. The optimum treatment concentration was 0.15 mol/L. Dynamic mechanical analysis tests indicated when AP modified by SiO2, the E' is higher due to the uniformly diffusion and enhanced interfacial adhesion for load transfer from the epoxy to AP. But Tg is lower as the flexibility chain Si-O-Si in epoxy. In comparison with the properties of the unmodified AP, the tensile strength and modulus of modified pulp/epoxy composites increased by 53.5% and 160.4%, respectively. Therefore, the dispersion and interface combination of AP modified by SiO2 in the epoxy improved because of the interaction of AP with SiO2 through the hydrogen bonding and crosslinking of SiO2 with epoxy.