The nucleophility as the determining parameter in the curing of epoxy resins

The reaction behaviour of epoxides was investigated using model reactions. For these, a monofunctional cresole epoxide was selected to be used and its reaction behaviour with compounds containing different functional groups was observed. The results of the investigations indicate that the nucleophilicity of the functional groups is the determining parameter in curing of epoxy resins. The most reactive were aromatic mercapto groups. When using amines, the primary amino groups are the first to react followed by secondary amino groups of hardeners. The secondary amino groups of reaction products (Beta-aminoalcohols) formed are less reactive and the lowest reactivity in these systems is shown by hydroxy groups of theses Beta-aminoalcohols. Thus it is concluded that in the first step of a reaction with primary diamines bifunctional epoxides always form linear polymers. It is also shown that cross-linking via secondary amino groups occurs more easily with increasing curing temperature. An ad ditional cross-linking via additions of hydroxy groups only becomes possible with increasing cure temperature, but the amine additions are still preferred.