Journal of Applied Polymer Science, Vol.56, No.11, 1511-1517, 1995
Effects of Physical Aging and Carbon-Dioxide Absorption in Bisphenol-A Polycarbonate
Thermal and mechanical behavior of bisphenol-A polycarbonate was studied as a function of thermal history and absorbed mass fraction of CO2. Physical aging at 120 degrees C for one week produced dramatic changes in both the thermal and mechanical behavior. Gas absorption studies indicated that although initial diffusion was somewhat retarded in the aged samples, both aged and unaged polycarbonate samples showed identical equilibrium absorbed gas values at 6500 K Pa and identical gas desorption behavior. Absorbed CO2 was shown to dramatically reduce the glass transition of polycarbonate indicating that CO2 plasticizes polycarbonate. Additionally, samples which had been aged and absorbed a mass fraction of 0.07-0.10 of CO2 showed thermal and mechanical behavior identical to that of a glass quenched from above T-g with identical absorbed mass fraction. Once the absorbed gas was desorbed, the thermal and mechanical properties were similar to those of a glass freshly quenched from above T-g. This study demonstrates that sufficient CO2 gas absorption followed by desorption reverses physical aging in polycarbonate.