Predicting the complex cure and gelation behaviour of epoxy resins used in generator stator insulation systems

Predicting the complex cure and gelation behaviour of epoxy resins used in generator stator ground wall insulation systems is necessary if the manufacturing conditions and final properties of the insulation system are to be optimized. While it is possible to obtain a variety of measurements of cure behaviour using bulk probing of the insulation system it is also important to follow the chemistry of the cure process up to and beyond the gel point and to relate the evolution of physical properties to the chemical conversion process during crosslinking and network formation. Here we describe a variety of molecular spectroscopic and calorimetric investigations into the isothermal and non-isothermal reaction kinetics of a bisphenol-A epoxy-anhydride system accelerated with a carboxylic acid salt. It is shown that the detailed cure process and reaction kinetics can be modelled to produce a predictive tool to describe the complete reaction process for any time-temperature cycle as a function of the accelerator concentration. Generalisation of these findings to the reaction behaviour of mica tape systems utilizing the same resin system is also discussed.