The Apparent Second‐Order Transition Point of Polystyrene
作者:
T. Alfrey,
G. Goldfinger,
H. Mark,
期刊:
Journal of Applied Physics
(AIP Available online 1943)
卷期:
Volume 14,
issue 12
页码: 700-705
ISSN:0021-8979
年代: 1943
DOI:10.1063/1.1714949
出版商: AIP
数据来源: AIP
摘要:
(1) At high temperatures (above 80°C) the specific volume of polystyrene is an explicit function of the temperature.dV/dT=0.00043. (2) At low temperatures (below 40°C) the specific volume of polystyrene depends upon its past thermal historydV/dT=0.00024, althoughVis not explicitly fixed by the temperature alone. (3) When a sample of polystyrene is cooled at constant rate, it contracts according to the higher expansion coefficient until some critical region of temperature, and then contracts according to the smaller coefficient. (4) Thepositionof the critical temperature region depends upon the rate of cooling. The faster the cooling, the higher the ``transition point.'' (5) In the intermediate temperature range (say 40°C to 80°C), complex time effects can be observed. A sample heated from 20°C to this intermediate range will first expand, according to the small expansion coefficient, and then contract slowly toward a smaller volume. The rate of this contraction is greater at higher temperatures. (6) All the observations are in fair accord with the interpretation of the ``second‐order transition point'' of polystyrene as the temperature at which rate of volume change becomes comparable with the experimental time scale.
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