Structural recovery of polymer glasses

Abstract

AbstractThe structural recovery of polystyrene glasses subjected to thermal cycles in the glass transition region is studied by differential scanning calorimetry and by dilatometry. Three different types of behaviour are observed in respect of the peak in the specific heat capacity or thermal expansion coefficient on heating, and are found to be in full agreement with the predictions of the KAHR model. First, for well‐stabilized glasses, the dependence of the (main) peak temperature on heating rate and annealing time yields consistent values for the structure parameter x by means of the peak‐shift method. Second, for poorly‐stabilized glasses, the (upper) peak temperatures shift quite differently, but again consistently with theory. Third, for glasses intermediate between poorly‐and well‐stabilized conditions, both main and upper peaks can be observed simultaneously in the same endotherm.