Enhancing epoxy/silica composite properties with a novel biomass-based silane coupling agents synthesized via thiol-ene reaction

This study aims to synthesize a novel biomass-based silane coupling agent (SCA) and apply it to epoxy/silica composites (ESCs) for performance evaluation in comparison with commercial SCAs. The novel biomass-based SCA was prepared by epoxidation of cinnamyl alcohol (CA) extracted from cinnamon leaves, followed by a thiol-ene reaction with (3-mercaptopropyl)trimethoxysilane (MPTS). The chemical structure of the synthesized SCA was characterized using Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. This synthesized SCA was applied to ESCs, and its performance was compared to that of ESCs utilizing three different commercial SCAs. The experimental results showed that the viscosity of the ESC mixtures with the synthetic SCA decreased by 19.6%. Additionally, observations of the fractured surface revealed that the synthetic SCA participated in the curing system of the epoxy resin, enhancing interfacial interactions and causing the silica particles to be covered by the epoxy resin, making them no longer visible. This enhanced interfacial interaction, driven by the participation of the synthetic SCA in the curing system, improved the cross-linking density of the epoxy resin, contributing to an increase in the glass transition temperature (Tg), the temperatures corresponding to 5% weight loss (T5%), and tensile strength of the ESC by 18.5 degrees C, 10.8 degrees C, and 49.7%, respectively. These results support that the synthetic SCA improved the compatibility and bonding strength between the epoxy resin and silica and demonstrate its potential as a replacement for commercial SCAs.Highlights A novel biomass-based SCA (CA-SCA) was synthesized for ESC. The chemical structure of CA-SCA was confirmed via FT-IR and 1HNMR. CA-SCA participated in the curing reaction, bonding epoxy resin and silica. CA-SCA has improved the thermal and mechanical properties in ESC.