Thermodynamic Analysis of Phase Separation of a Thermoplastic in the Precursors of Different Epoxy‐Amine Systems

Abstract

Abstract The miscibility of a thermoplastic, polystyrene (PS), with the precursors of several epoxy‐amine systems has been studied thermodynamically and experimentally. The epoxy‐amine systems were different only in the origin of amino groups, which were provided by a monoamine (MA) and a diamine (DA) in different proportions. Cloud‐point curves (CPC) at conversion zero were reported for five modified systems with different MA‐DA proportion. All CPCs showed an UCST behaviour. CPC shifted to lower temperatures when the ratio of MA/DA in the system increased, meaning that the MA produces an increase in the miscibility of the system. A model based on the Flory‐Huggins theory was used for the thermodynamic analysis, in which the dependence of interaction parameter on temperature and composition, χ (T, ϕ ), and the polydispersity of components were considered. A general equation for χ (T, ϕ ) also depending on the MA‐DA proportion was reached and used to obtain the phase diagram of the different systems. A high level of agreement between theoretical and experimental CPCs was obtained.