Abstract
The origin of two maxima in specific heat observed at the higher and the lower temperatures in the glass-transition region in the heating process has been studied for polymethyl methacrylate and polyvinyl chloride using differential scanning calorimetry, and the calculation was done using the phenomenological model equation under a thermal history of the typical annealing experiment composed of cooling, annealing, and heating. The higher maximum is observed above the glass-transition temperature, and it remains almost unchanged independent of annealing time , while the lower one is observed above an annealing temperature and shifts toward the higher one, increasing its magnitude with . The analysis by the phenomenological model equation proposed in order to interpret the memory effect in the glassy state clarifies that under a typical annealing history, two maxima in specific heat essentially appear. The shift of the lower maximum toward higher temperatures from above is caused by an increase in the amount of relaxation during annealing with . The annealing temperature and the amount of relaxation during annealing play a major role in the determination of the number of maxima in the specific heat.
3 More- Received 24 June 2016
- Revised 6 November 2016
DOI:https://doi.org/10.1103/PhysRevE.94.062501
©2016 American Physical Society