Robust Heat-Free Curing via ‘SiNergy’ in Action: Residual Cure Kinetics and Thermal Stability of Epoxy Silicon Nitride / Tungsten Carbide Dual Filler Nanocomposites

This work explores the synergistic effects of SiN and WC nanofillers on the residual curing behaviour and thermal degradation of epoxy (EP). DSC was used to evaluate residual curing characteristics, while TGA assessed thermal stability. HR-TEM confirmed that both nanofillers were uniformly dispersed and exhibited strong inter-particle and matrix interactions, suggesting effective integration into EP. The 0.5 wt% SiN/EP (ES2) exhibited near-to-complete curing, attributed to the hotball mechanism of silicon nitride (SiN), enhancing localized heat transfer which promotes crosslinking reactions. Tungsten carbide (WC) demonstrated minimal influence on the curing process, acting as a thermally inert filler in this context. However, the 0.25 wt% and 0.5 wt% of SiN/WC in EP showed improved curing efficiency compared to WC-based composites, confirming a synergistic interaction between the fillers. The activation energy (Ea) for residual curing was determined using model-free methods, such as the Kissinger and Ozawa methods, among others. ES2 displayed the lowest residual content with the highest Ea, suggesting more complete curing. Thermal degradation kinetics was studied using the Horowitz-Metzger, Coats-Redfern, and Friedman models. Among all formulations, the hybrid nanocomposite demonstrated superior thermal stability, attributed to the enhanced crosslink density induced by SiN and the good thermal barrier property of WC. The combined effect of these nanofillers resulted in increased activation energy for decomposition, indicating improved resistance to thermal degradation. These findings highlight the potential of combining SiN and WC nanofillers to engineer epoxy with enhanced curing efficiency and thermal durability, making them promising candidates for high-performance applications.