Surface Roughening of Irradiation-Activated Basalt Fiber through In Situ Growth of SiO2: Effects on Crystallization and Properties of PP Composites

Basalt fiber (BF) is deemed a new environmentally friendly and high-performance fiber material due to its high strength, electrical insulation, corrosion resistance and high temperature resistance. Yet, the surface inertness restricts its practical application. In this work, the BF was irradiated and activated by electron beam, followed by in situ growth of SiO2 using a hydrothermal method, then composites with polypropylene (PP) were prepared by microinjection molding. According to the results of scanning electron microscopy (SEM) and Fourier transform infrared (FTIR), more active sites can be formed after irradiation, thus more SiO2 nanoparticles were generated on the surface of BF. Consequently, the rough surface of modified BF could provide stronger shear force during melt processing and resulted in a higher orientation of the molecular chains, increasing the lamellar thickness and generating more highly ordered beta crystals in the composites. I400BF-gSiO(2) exhibited the highest content of beta crystals with the crystallinity of 53.62% and orientation of beta (300) crystal plane of 0.91, which were 8.66% and 0.04 higher than those of the composite with pristine BF. Furthermore, due to the perfection of crystals, increased interfaces and interfacial interlocking between PP molecules and modified BF, I400BF-gSiO(2) showed good overall performance, with storage modulus of 8000 MPa at 100 degrees C, glass transition temperature of 23.03 degrees C and tensile strength of 62.2 MPa, which was 1900 MPa, 1.23 degrees C and 29.6 MPa higher than neat PP. Hence, the surface roughing strategy proposed in this work is expected to provide some insight and promote the application of BF reinforced thermoplastic composites.