Reaction induced phase separation in semicrystalline thermoplastic/epoxy resin blends

The phase separation behaviour and phase morphology of blends of 4,4′-diaminodiphenyl sulphone cured diglycidyl ether of bisphenol-A with poly(ε-caprolactone) were investigated by means of scanning electron microscopy, small angle light scattering and optical microscopy. The components are miscible prior to curing. High-temperature isothermal curing induces phase separation. Blends with near to critical concentrations demix via spinodal decomposition. The associated co-continuous morphology is only preserved in the actual critical compositions whereas for off-critical compositions it rapidly breaks up into spherical particles. The proceeding reaction in the separated phases induces a secondary phase separation. Occasionally, tertiary phase separation is observed as well. Off-critical compositions that are further away on either side from the critical point, phase separate via the direct formation of spherical particles, most likely as a result of the dynamic asymmetry of these blends. The influence of the amount, the molar mass of PCL and the cure temperature is discussed.