Characterization and properties of SiO₂-coated graphene/bismaleimide composites

The silane coupling agent vinyl trimethoxysilane (VTMO) was used to modify graphene (GE), and SiO₂ microspheres were coated on the surface of graphene by sol-gel method to obtain SiO₂-coated modified graphene (SiO₂@(VTMO-GE)). The 4,4′-diaminodiphenyl methane bismaleimide-diallyl bisphenol A-bisphenol A bisallyl ether (BBA-BBE-MBMI, MBAE) matrix was synthesized from BBA, BBE and MBMI, in which BBA and BBE were used as reactive diluents and MBMI was used as the monomer. The MBAE modified by SiO₂-coated graphene (SiO₂@(VTMO-GE)/MBAE) composites were prepared by in-situ polymerization with SiO₂@(VTMO-GE) as the reinforcement. The effect of SiO₂@(VTMO-GE) on the properties of the SiO₂@(VTMO-GE)/MBAE composite was studied by characterizing and analyzing the VTMO-GE and the coating effect. The results show that GE is successfully modified by VTMO, and SiO₂ microspheres are uniformly coated on the surface of VTMO-GE. The SiO₂@(VTMO-GE) component improves global properties of the SiO₂@(VTMO-GE)/MBAE composite. The impact strength and bending strength of the SiO₂@(VTMO-GE)/MBAE composite reach the maximum of 23.0 kJ/m² and 157.4 MPa, respectively, which are 150% and 58% higher than that of the MBAE, when the content of SiO₂@(VTMO-GE) is 2.0wt%. The dielectric constant and the dielectric loss are about 70.0 and 3.7×10^–3 in the frequency range of 10²–10⁴ Hz, while the heat resistance enhances with the increase of SiO₂@(VTMO-GE) amount. The SiO₂@(VTMO-GE)/MBAE composite exhibits excellent global properties and lays the foundation for further application.