Interphase formation in model composites studied by micro-thermal analysis

Micro-thermal analysis was used for studying interphases formed in particle-filled composites based on an epoxy resin matrix. The subsurface distribution of the particles can be observed in the conductivity images, while spatial variations in thermal properties can be determined by local thermal analyses. anhydride-cured epoxy system filled with porous silica particles, an interphase is observed around the particles. In the ca. 60 μm wide interphase, the glass transition temperature gradually decreases from the bulk value to a value about 10 °C lower. The less densely cross-linked interphase can be detected in the thermal conductivity images and in the local thermal analyses. The interphase formation is attributed to the effect of adsorbed water on the polymerisation mechanism.