3621 -- Absorption of HCFC-123 and CFC-11 by Epoxy Motor Varnish PDF

Because of compatibility concerns with motor varnishes and refrigerants, a study was initiated to determine the effect of various parameters on the absorption of HCFC-123 and CFC-11 by epoxy motor varnishes. Absorption of refrigerant continues to increase until equilibrium is established and then remains constant. There is no apparent difference between a continuous exposure to refrigerant as compared to a cyclic exposure involving cooling and removal of the varnish by introduction into the refrigerant. Desorption of moderate amounts of refrigerant is extremely slow to nonexistent at room temperature and would require many days for complete removal of refrigerant at 250 deg F. The rate of attainment of equilibrium absorption is different for each varnish and is more rapid at higher temperatures. The rate varies from a few days at 250 deg F to many months at 150 deg F. The equilibrium absorption value for HCFC-123 is linearly dependent on temperature, with greater absorption at lower temperatures. The equilibrium absorption of CFC-11 appears to be relatively independent of temperature. Because of the greater absorption of HCFC-123 at lower temperatures, care must be exercised in compatibility studies. Low-temperature exposure to refrigerant may be a more severe condition than high temperature and pressure. A long period of time may be required for the full effect of low-temperature exposure to be manifested.

KEYWORDS: absorption, R123, R11, refrigerants, epoxy resins, motors, low temperature, high temperature, exposure, room temperature, equilibrium