Thermal analysis of some aromatic amine cured model epoxy resin systems .2. Residues of degradation

The thermal and thermo-oxidative stability of thermoplastic and thermoset epoxy resin model systems based on the diglycidyl ether of bisphenol A (DGEBA) are compared and contrasted as a function of (mostly) aromatic amine curative structure. Overall activation energies for thermal degradation were measured for selected model systems using programmed thermogravimetry, in conjunction with the Flynn-Wall and Kissinger methods of data reduction, and were used to establish correlations between thermal stability and curative structure, resin crosslink density and cure stoichiometry. The thermal degradation of poly(bisphenol A, 2-hydroxy propyl ether) 'Phenoxy'(tm) resin, a simpler bisphenol A-containing model system which remains soluble throughout the weight loss process in the absence of oxygen, was characterised through joint application of thermogravimetry, capillary viscometry, high resolution H-1 and C-13 Nuclear Magnetic Resonance spectroscopy and Infrared (IR) spectroscopy. Processes of thermal degradation and thermo-oxidative degradation of Phenoxy(tm) resin, and of network and thermoplastic epoxy resin model systems, were examined through the application of IR spectroscopy. The 1,3 di-phenoxy isopropanol chain extender in Phenoxy(tm) resin was shown to be more stable than the di-(3-phenoxy, 2-hydroxy) tertiary aromatic amine extender/crosslink in DGEBA based epoxy resins, both in the presence and in the absence of oxygen. (C) 1996 Elsevier Science Limited