Phase separation and morphology development in a thermoplastic-modified toughened epoxy

The morphologies developed by blends based on a polystyrene modifier and an epoxy system polymerized with a monoamine and a diamine mixed in different proportions that are phase separated during the polymerization, were studied. The proportion of monoamine–diamine in the system affects the crosslinking degree of the material, which was controlled and continuously modified from a linear polymer to a highly crosslinked polymer. The effect of modifier proportion, polymerization temperature, and monoamine–diamine ratio on the final morphology was investigated. Different types of morphologies were developed depending mainly on the composition of modifier in the blend. The nature of the separated phases in the different types of morphologies was investigated and confirmed by experiments with a solvent and elemental analysis. Explanations for the developed morphologies as a function of the variables were proposed and discussed in detail.