Curing characteristics of an epoxy resin in the presence of ball-milled graphite particles

The effects of simply-made graphite particles (GPs, 1 wt%) on curing kinetics of an epoxy resin were investigated by means of differential scanning calorimetry (DSC). Two approaches based on constant and variable activation energy were applied to analyze the DSC curves. Results from the constant energy method showed that addition of the GPs increased the activation energy E_c and the overall order of reaction m + n. With the variable energy method, the activation energy varied with curing conversion substantially in the GP/epoxy system; in contrast, the variation in the pure epoxy was very limited. The GPs also decreased the heat of reaction (ΔH) and increased the glass transition temperature (T_g) for the epoxy. Comprehensive analyses indicated that the GPs did not significantly impede the curing reaction, which can enable improvement of the composite functionalities without creating processing penalties. The information obtained from this study provides an understanding of multiple factors involved in the complex relationship of structure and properties of the composites.