Confocal microscopy study of phase morphology evolution in epoxy/polysiloxane thermosets

The morphology of stoichiometric initially immiscible reactive blends of DGEBA epoxy resin and poly(3-aminopropylmethylsiloxane) has been characterized by laser scanning confocal microscopy. Observations were done on samples cured isothermally at different curing temperatures in the range 20–120 °C as well as in situ and in real time at 60 °C. Three different processes were revealed: coalescence, which occurs primarily at very low conversion, diffusion of DGEBA through polysiloxane-rich domains and chemical reaction, which occurs at the interphase between both phases. The interphase-thickness and compositional gradients were characterized by laser scanning confocal microscopy (LSCM). Results show that as curing temperature increases within the studied range, the material becomes more homogeneous although the interphase thickness remains almost constant.