Effect of temperature on physical aging of thin glassy polymer films

The effect of temperature on the kinetics of physical aging of thin films formed from two amorphous glassy polymers, polysulfone based on bisphenol A and poly(2,6-dimethyl-1,4-phenylene oxide), was investigated by monitoring the changes in gas permeability and refractive index. Films with different thicknesses were subjected to isothermal aging at three temperatures, ranging from 35 to 55 degrees C, for a period of aging of more than 200 days. The rate of permeability loss and the rate of densification determined from the refractive index change by using the Lorentz-Lorenz equation were found to increase with aging temperature. Similar qualitative trends of aging rate were noted by the two measurements. The combination of effects of aging temperature and film thickness on aging behavior were studied and compared with previous research.