AbstractThe generalization of a multiordering parameter model to treat physical aging in polymeric glasses is more fully explored. In the past, this model has successfully rationalized most aspects of time dependent volume and enthalpy behavior; however, only qualitative agreement between predictions of the generalized model and experiment were previously achieved for physical aging. Now, by paying strict attention to the specific analytical form of the shift factor expression, quantitative predictions have been realized for physical aging behavior based on evaluations of the shift factor parameters using volumetric data. The model also reproduces the observed behavior of glasses subjected to more complex thermal treatment such as those which evoke “memory” in glasses, e.g., shift reversal and nonmonotonic variations of the steepness of relaxation curves in the primary transition region.