Abstract
The curing behavior of bisphenol-A type epoxide oligomers (Ep) was evaluated by DSC in the presence of S-alkyldiphenylsulfonium salts as a thermal latent initiator. These initiators are soluble in Ep to obtain the homogeneous solutions and the curing reaction of the resulting mixtures occurred on heating. The initiation activity of these salts was controllable by the character of the S-alkyl group and of the substituents on the benzene ring. Namely, the stability of carbocation released from the sulfonium salts and the electron density on the sulfide affect the initiating temperature. A good correlation was obtained between the initiating temperature and the electron density of the sulfur atom of the corresponding sulfide estimated from ab initio molecular orbital calculation. It showed the initialing temperature becoming higher as the electron density of the sulfur atom increased.
