Non-equilibrium processes in poly(vinyl chloride) glasses vitrified at elevated pressures
| Autor: | F. J. Roberts, William M. Prest, J. M. O'Reilly, R. A. Mosher |
|---|---|
| Rok vydání: | 1981 |
| Předmět: |
Exothermic reaction
Materials science Polymers and Plastics Annealing (metallurgy) Thermodynamics General Chemistry Endothermic process Vinyl chloride chemistry.chemical_compound Differential scanning calorimetry chemistry Materials Chemistry Organic chemistry Vitrification Fourier transform infrared spectroscopy Glass transition |
| Zdroj: | Polymer Engineering and Science. 21:924-924 |
| ISSN: | 1548-2634 0032-3888 |
| DOI: | 10.1002/pen.760211408 |
| Popis: | The conformational and enthalpic changes that occur in poly(vinyl chloride) (PVC) glasses that have been vitrified from the melt under pressure have been examined by Fourier transform infrared spectroscopy and quantitative differential scanning calorimetry. It is shown that these pressures freeze in the high energy states that are characteristic of the vitrification temperature and increase the apparent glass transition temperature of the polymer. In addition, pressures in excess of the vitrification pressure, cause intermolecular effects that can be relaxed out below Tg. Both of these processes create characteristic endothermic and exothermic changes in the apparent heat capacity of the glass that appear over a period of time and are sensitive functions of the glass formation processes as well as the subsequent annealing history. The endothermic events are interpreted as the stress perturbed volumetric relaxation process white the exotherms are associated withh the release of the frozen in stresses. |
| Databáze: | OpenAIRE |
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