The improvement mechanism of styrene grafted nano-Al2O3 on the hydrophobicity of epoxy resin composites: Based on molecular dynamics and experimental research

In the environment with high humidity, water will penetrate into the epoxy resin, resulting in the deterioration of the electrical properties and the decreasing resistance for the heat and corrosion. This study aims to utilize styrene grafted Al2O3 to improve the wettability of the epoxy resin surface and reduce the infiltration of water molecules into the epoxy resin interior. Firstly, the effects of doping PS/Al2O3 on the internal structure of epoxy resin and the diffusion process of water molecules within it are analyzed through the method of molecular dynamics (MD). Subsequently, epoxy resin samples with mass fractions of 1%, 3%, and 5% are prepared, followed by testing for hydrophobicity, water absorption, and the quality of surface condensation under different temperature differentials. The results indicate that the PS/Al2O3 and epoxy resin exhibit a strong interaction, reducing the proportion of free volume fraction of epoxy resin, which lowers the diffusion rate of water molecules. To be specific, the nanoparticles capture water molecules by forming hydrogen bonds with them, limiting the displacement of water molecules and reducing the water absorption of the epoxy resin (maximum reduction of 87%). Moreover, the addition of PS/Al2O3 decreases the adhesion energy of the material surface to water molecules, increasing the static contact angle from 103.58 degrees to 125.42 degrees. Additionally, the total weight of condensation droplets on the material surface is reduced (maximum reduction of 26.02%). These findings serve as a reference for modifying epoxy resin materials in hygrothermal environments.