Preparation, curing, and properties of boron-containing bisphenol-S formaldehyde resin/o-cresol formaldehyde epoxy resin/nano-SiO2 composites

Boron-containing bisphenol-S formaldehyde resin (BBPSFR) with different amounts of nano-SiO2 by in situ formation was used to cure o-cresol formaldehyde epoxy resin (o-CFER). The curing kinetics, dynamic mechanical properties, and thermal stability of BBPSFR/o-CFER/nano-SiO2 composites (BCS) were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetry (TG), and thermogravimetrymass spectrometry (TGMS). Morphology of nano-SiO2-containing BBPSFR and glass fiber laminates of the BCS were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The mechanical properties and electrical properties were also determined. The results showed that nano-SiO2 accelerated the curing process and decreased the curing temperature; the non-isothermal curing kinetics of the BCS can be described by the two-parameter (m, n) Sestak-Berggren kinetic model, and the average value of m was 0.32 and n was 1.00. The thermal stability was enhanced by the addition of nano-SiO2, especially at higher temperatures, and the residual weight increased with increasing nano-SiO2 content. Incorporation of 6 wt% of nano-SiO2 increased the impact strength from 105 to 149 kJ/m2 and storage modulus at ambient from 6.85 to 12.7 GPa, and the TEM photograph of which showed that nano-SiO2 particles (about 50 nm) were dispersed in the matrix more uniformly. The volume resistance, R v, and dielectric constant, e, slightly increased when the nano-SiO2 content was 3 wt%.