Thermodynamic analysis of phase separation of a thermoplastic in a variant epoxy/monoamine-diamine system: influence of epoxy molecular structure

Abstract

Abstract A thermodynamic study of phase separation induced by the polymerization process was carried out in a variant epoxy/amine system modified with polystyrene (PS) by means of a model based on the Flory-Huggins theory in which the polydispersity of components was taken into account. Modification of the epoxy/amine system was to continually change its molecular structure from a linear polymer to a highly crosslinked polymer using a monoamine and a diamine mixed in different proportions. The cloud-point curves during polymerization for five epoxy/monoamine-diamine systems with PS blends were experimentally measured. Application of the thermodynamic model led to obtaining the corresponding phase diagrams. All studied blends showed an upper critical solution temperature behavior and an increase in miscibility was observed by increasing the monoamine/diamine ratio. The polydispersity of components caused a molecular fractionation leading to a difference in the conversion of separate phases.