Cationic polymerization of diglycidly ether of bisphenol a resins initiated by benzylsulfonium salts

Benzylsulfonium salts are latent thermal cationic initiators that dissociate on heating to form benzyl cations that can initiate polymerizations. This paper describes the cure behavior of commercial epoxy resins using 1 ‐( p ‐methoxybenzyl)tetrahydrothiophenium hexafluoroantimonate [ 2 ]. The thermal cationic cure of bisphenol A diglycidylether (DGEBA) resins was investigated using differential scanning calorimetry (DSC). DSC revealed complex cure behavior as indicated by multiple exotherms. The resins cured rapidly at low initiator concentrations with gelation occuring in 3.5 and 1.5 min at 75 and 85 °C, respectively, at conversions of epoxy groups α = 0.2–0.3. Cure kinetics were evaluated from both dynamic and isothermal DSC measurements. The effects of initiator concentration, isothermal cure temperature and heating rate on the cure behavior and mechanisms, especially involving potential termination pathways, are discussed.