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Non‐equilibrium processes in poly(vinyl chloride) glasses vitrified at elevated pressures
Author(s) -
Prest W. M.,
O'Reilly J. M.,
Roberts F. J.,
Mosher R. A.
Publication year - 1981
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760211802
Subject(s) - endothermic process , vitrification , vinyl chloride , differential scanning calorimetry , exothermic reaction , materials science , glass transition , polymer , thermodynamics , annealing (glass) , fourier transform infrared spectroscopy , polymer chemistry , chemical engineering , composite material , chemistry , adsorption , physics , engineering , medicine , copolymer , andrology
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 T g . 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.