Curing-induced filler aggregation in epoxy-amine systems

Abstract

Polymer coating materials, such as paints, inks, and adhesives, are applied in a liquid state and form solid films through curing reactions. During the curing process, aggregation of filler particles dispersed in the matrix is often enhanced, yet the parameters governing this behavior remain unclear. In this study, we directly observed the three-dimensional configurations of fluorescent polystyrene particles before and after curing in an epoxy–amine system using confocal laser fluorescence microscopy. The aggregation fraction was quantitatively evaluated by varying the filler volume fraction and particle size a[jls-end-space/]. The results indicate that curing promotes filler aggregation that cannot be fully explained by conventional short-range attractive interactions alone. Furthermore, the increase in aggregation fraction cannot be described solely by the filler volume fraction, but is better organized by the mean interparticle gap, H[jls-end-space/]. The particle-size dependence further indicates that the relevant distance scale for aggregation is on the order of the particle size. In addition, the aggregation increment tends to increase with decreasing (Formula presented). These findings highlight interparticle spacing as a useful geometric parameter for describing curing-induced aggregation in curing-based polymer composite systems.