Thermal analysis of some aromatic amine cured model epoxy resin systems .1. Materials synthesis and characterization, cure and post-cure

A selection of small, large and network epoxy resin model systems were prepared and characterized structurally. X-ray crystallography was used to establish that a conformation available to the RS diasteriomer of the di-beta-hydroxy, sp(2) hybridized tertiary amine structural motif, common to aromatic amine-glycidyl ether epoxy resin systems, is capable of engaging in intramolecular H-bonding. NMR spectroscopy was used to confirm the existence of strong intramolecular II-bonding in the RS diasteriomer and support the presence of weaker intramolecular II-bonding interactions in the RR=SS diasteriomer. It was illustrated, through the use of more complex model compounds and soluble polymers, that the structure-NMR spectroscopic correlations established in simpler models should extrapolate into 3-dimensional epoxy network systems. DMA spectroscopy was used to establish that changes in crosslink density of stoichiometric epoxy resin model systems, brought about through changes in hardener formulation, influence the energetics of the alpha and beta transitions as quantified through E(a), Delta H# and Delta S#. It was established also that changes in the chemical composition of epoxy resin model systems, brought about through changes in reagent stoichiometry, have a more significant influence on the energetics of measured thermal transitions as quantified by this method. (C) 1996 Elsevier Science Limited