REACTIONS IN AMINOSILANE EPOXY PREPOLYMER SYSTEMS .1. KINETICS OF EPOXY AMINE REACTIONS

The reactions of an epoxy prepolymer based on bisphenol A diglycidylether (DGEBA) with gamma-aminopropyltriethoxysilane (gamma-APS) are studied. The results of different techniques are compared: size exclusion chromatography, differential scanning calorimetry, chemical titration, and Fourier Transform Infrared absorption. Epoxy amine reactions are shown to be faster than the crosslinking reactions between alkoxysilane and hydroxy groups, and thus, can be studied separately. The reactivity of the epoxy group in DGEBA is compared with that of phenylglycidylether (PGE). And the reactivity of the amine group of gamma-APS is compared with that of hexylamine. The kinetic constants are calculated with a mechanism which takes into account both the catalytic and noncatalytic reactions. The ratio r = k2/k1 of the reactivity of the secondary to the primary amino-hydrogens was also determined. The values of r are 1.4 for hexylamine and 1.2 for gamma-APS. The reactivities of the epoxy groups are the same for both PGE and DGEBA.