Method of exposing and curing an epoxy composition containing an aromatic onium salt

A method for effecting the cationic polymerization of epoxy resin which comprises,

• (1) forming a mixture consisting essentially of epoxy resin and an effective amount of a radiation sensitive aromatic onium salt of a Group Va element of the formula,
• [(R).sub.a (R.sup.1).sub.b (R.sup.2).sub.c X].sub.d.sup.+ [MO.sub.e ].sup.-(e-f),
• which is capable of effecting the cure of such mixture when exposed to radient energy,
• (2) exposing said mixture to radiant energy to effect the cure of the organic material,
• where R is a monovalent aromatic organic radical selected from carbocyclic radicals and heterocyclic radicals, R.sup.1 is a monovalent organic aliphatic radical selected from alkyl, alkoxy, cycloalkyl and substituted derivatives thereof, R.sup.2 is a polyvalent organic radical forming an aromatic heterocyclic or fused ring structure with X, X is a Group Va element selected from N, P, As, Sb and Bi, M is a metal or metalloid, Q is a halogen radical, a is a whole number equal to 0 to 4 inclusive, b is a whole number equal to 0 to 2 inclusive, c is a whole number equal to 0 to 2 inclusive, and the sum of a+b+c is a value equal to 4 or the valence of X,
• d=e-f
• f=valence of M and is an integer equal to from 2 to 7 inclusive
• e is >f and is an integer having a value up to 8.