Tuning morphologies of thermoset/thermoplastic blends - Part 2: Phase separation of poly(vinyl methyl ether), PVME, using amine mixtures as thermoset hardeners
Résumé
Part 2 of the study investigates morphologies of epoxy thermoset / thermoplastic blends obtained with formulations of the thermoset hardeners. The thermosetting matrices are composed of one epoxy resin crosslinked by a mixture of two aromatic diamine hardeners, namely MCDEA+DDS or MDEA+DDS (DDS is 4,4'-diaminodiphenylsulfone, MCDEA is 4,4'-methylenebis-(3-chloro-2,6-diethylaniline), MDEA is 4,4'-methylenebis-(2,6-diethylaniline). The blends are made at a fixed concentration of thermoplastic ( poly( vinyl methyl ether), PVME, 10wt%) whereas three different cure temperatures are chosen and the matrix composition is varied by the ratio of DDS. DDS is a PVME-insoluble diamine whereas MDEA or MCDEA are PVME-soluble diamines. The domain size of the PVME nodules is tuned from a few micrometers down to sub micron sizes, typically between 50 and 80 nm. We attempt to explain this evolution thanks to the difference in the reactivity of the amines with the epoxy oligomer coupled to the difference in miscibility of each amine towards PVME. The kinetic study developed in Part 1 of this work is used to calculate the concentrations of each amine along the reaction time and their rate of incorporation in the polymer network. The latter parameter is shown to be the limiting factor for obtaining a nano phase separation.