KH550, KH560, and KH570 modified SiO2 enhance the moisture resistance, thermal properties and electrical insulation properties of epoxy resin: Based on experiments and molecular dynamics simulations

In this study, the enhancement mechanism of SiO 2 modified by different silane coupling agents (SCA) on the moisture resistance, thermal properties and electrical insulation properties of epoxy resin (EP) composites is discussed. Through the combination of experimental tests and molecular dynamics (MD) simulations, the performance differences of five systems (EP, SiO 2 -EP, KH550 / SiO 2 -EP, KH560 / SiO 2 -EP, KH570 / SiO 2 -EP) in water absorption, glass transition temperature ( T g ) and volume resistivity are analyzed. The changes of free volume fraction (FFV), interaction energy, number of hydrogen bonds and diffusion behavior of water molecules are revealed from the microscopic point of view. The experimental results show that the introduction of modified SiO 2 significantly improves the moisture resistance, thermal properties and electrical properties of EP. Among them, KH550 modified SiO 2 has the best effect, T g increases by 12.3 %, volume resistivity increases by 22.1 %, and water absorption rate decreases by 21.9 % at 60 °C. MD simulations further confirm that the nano-SiO 2 modified by SCA can effectively limit the diffusion of water molecules and reduce the effect of temperature on the mean square displacement (MSD) of the system. The KH550 / SiO 2 -EP system has the smallest free volume and the highest number of hydrogen bonds, which effectively inhibits the diffusion of water molecules and the movement of molecular chains. This study provides a theoretical basis and material design strategy for the application of epoxy composites in hygrothermal environments.