The Apparent Second-Order Transition Point of Polystyrene

Abstract

(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 history dV/dT=0.00024, although V is 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) The position of 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.

Polymer Transport Properties

“…The kinetics of the lattice contraction are not dependent on the sample dimensions. The diffusion of free volume or holes was first proposed by Alfrey and co-workers (132). In this mechanism, packets of free volume are pictured as diffusing from the interior to the surface of the sample where they are eliminated.…”

Relaxation and viscoelastic properties of heterogeneous polymeric compositions

“…Of interest from this point of view is the examination of the effect of fillers on such relaxation processes in which sufficiently large structural elements take part. Those phenomena were studied (33,(45)(46)(47) by calculating the average relaxation time proceeding from the data on the isothermic contraction of the volume of various filled systems by the method proposed in (48).…”

Diffusion mechanism for physical aging of polycarbonate far below the glass transition temperature studied by means of dielectric spectroscopy

“…Still little is known, however, about the microscopic mechanisms of physical aging. In the early forties, Alfrey et al [5] proposed that diffusion of free volume holes towards the external surface of the sample could be responsible for the time evolution of the macroscopic thermodynamic properties. This hypothesis was later opposed by Braun and Kovacs [6], who found a weak, if any, geometry dependence of the aging process.…”