Monitoring the storage stability of large volumes of vacuum pressure impregnating resins

Catalyzed storage stability tests have been carried out with a series of vacuum pressure impregnation epoxy-anhydride solventless impregnants. The changes in viscosity with storage time were recorded for several of these resins. Replenishment storage tests, in which a 20% addition of fresh material was added every two weeks, were also carried out. The data obtained indicate that under the most severe manufacturing conditions anticipated in "shop" usage (i.e., 26°C and 0.25% H2O), the impregnants attain a steady-state viscosity condition after 10 weeks of storage. A theoretical discussion is presented in which empirical parameters are derived for these resins. Theoretical steady-state viscosity values are calculated for some of the impregnants and show good agreement with the experimentally derived ones.