ISOTHERMAL CURE OF AN EPOXY SYSTEM CONTAINING TETRAGLYCIDYL-4,4'-DIAMINODIPHENYLMETHANE (TGDDM), A MULTIFUNCTIONAL NOVOLAC GLYCIDYL ETHER AND 4,4'-DIAMINODIPHENYLSULPHONE (DDS) - VITRIFICATION AND GELATION

Times to gelation and vitrification have been determined at different isothermal curing temperatures between 200 and 240 degrees C for an ep oxy/amine system containing both tetraglycidyl-4,4'-diaminodiphenylmet han (TGDDM) and a multifunctional Novolac glycidyl ether with 4,4'-dia minodiphenylsulphone (DDS). The mixture was rich in epoxy, with an ami ne/epoxide ratio of 0.64. Gelation occurred around 44% conversion. Vit rification was determined from data curves of glass transition tempera ture, T-g, versus curing time obtained from differential scanning calo rimetry experiments. The minimum and maximum values T-g determined for this epoxy system were T-g0 = 12 degrees C and T-gmax = 242 degrees C . Values of activation energy for the cure reaction were obtained from T-g versus time shift factors, a(T), and gel time measurements. These values were, respectively, 76.2 kJ mol(-1) and 61.0 kJ mol(-1). The i sothermal time-temperature-transformation (TTT) diagram for this syste m has been established. Vitrification and gelation curves cross at a c ure temperature of 102 degrees C, which corresponds to glass transitio n temperature of the gel.