Thermally Conductive and Insulating Epoxy Composites by Synchronously Incorporating Si-sol Functionalized Glass Fibers and Boron Nitride Fillers

Glass fibers (GFs)/epoxy laminated composites always present weak interlaminar shear strength (ILSS) and low cross-plane thermal conductivity coefficient (lambda(perpendicular to)). In this work, silica-sol, synthesized from tetraethyl orthosilicate (TEOS) and KH-560 via sol-gel method, was employed to functionalize the surface of GFs (Si-GFs). Together with a spherical boron nitride (BNN-30), the thermally conductive BNN-30/Si-GFs/epoxy laminated composites were then fabricated. Results demonstrate that Si-sol is beneficial to the improvement of mechanical properties for epoxy laminated composites (especially for ILSS). The BNN-30/Si-GFs/epoxy laminated composites with 15 wt% BNN-30 fillers display the optimal comprehensive properties. In-plane lambda(lambda(//)) and lambda(perpendicular to) reach the maximum of 2.37 and 1.07 W center dot m(-1)center dot K-1, 146.9% and 132.6% higher than those of Si-GFs/epoxy laminated composites (lambda(//) = 0.96 W center dot m(-1)center dot K-1 and lambda(perpendicular to) = 0.46 W center dot m(-1)center dot K-1), respectively, and also about 10.8 and 4.9 times those of pure epoxy resin (lambda(//) = lambda(perpendicular to) 0.22 W center dot m(-1)center dot K-1). And the heat-resistance index (T-HRI), dielectric constant (epsilon), dielectric loss (tan delta), breakdown strength (E-0), surface resistivity (rho(s)) as well as volume resistivity (rho(v)) are 197.3 degrees C, 4.95, 0.0046, 22.3 kV center dot mm(-1), 1.8 x 10(14) O, and 2.1 x 10(14) O center dot cm, respectively.