Time-of-flight ion mobility measurements in epoxy-amine systems during curing

The technique based on the time-of-flight (TOF) concept was proposed for determination of ion mobility in epoxy resins under isothermal curing conditions. This study extends our earlier investigations on this subject. Ionic conductivity dc measurements also were carried out in order to gain better understanding of the evolution of the ionic conductivity and mobility. The experiments have been performed for selected epoxy-amine systems that gellify and vitrify: diglycidyl ether of bisphenol A (DGEBA) with 4,4'-methylenebis [3-chloro-2,6-diethylaniline] (MCDEA) and for reacting medium that gellify only: diglycidyl ether of 1,4-butanediol (DGEBD) with 4,9-dioxa-1,12-dodecane diamine (4D). The differences found between the time dependency of the ionic conductivity and mobility during curing are explained by the decrease of the concentration of ionic charge carriers during the reaction. We conclude that the decrease of the ionic charge carrier density during the reaction, limits the applicability of the basic assumption of electrical techniques for reaction monitoring, that the ionic conductivity is related directly to the medium viscosity.