Untersuchungen Über die Lineare Volumennachwirkung bei Amorphen Hochpolymeren

Abstract

Measurements of isothermal‐isobaric volume retardation occurring in atactic polystyrene after temperature and pressure jumps applied to the material are reported. The volume post‐effect could be measured at very small deviations from internal equilibrium and therefore linear retardation behavior was obtained. In this case, different kinetic theories give an exponential time dependence of volume deviation from the equilibrium value due to the presence of a single reatrdation time. This prediction was not corroborated by our experiments. It was found that the isothermal‐isobaric volume post‐effect could not be described, at least with styrene, by a single retardation time but that it was necessary to assume a retardation time distribution.

Volume Relaxation and the Lattice–Hole Model

“…The polymer is assumed to be in equilibrium at the initial pressure p 0 and temperature T. Then at time t = 0, the pressure is suddenly stepped to the final value p 1 without change in temperature. Rehage and Goldbach have measured the volume recovery following pressure steps from several elevated pressures down to atmospheric pressure at the temperature of 91.84 • C [Rehage and Goldbach, 1966;Goldbach and Rehage, 1967]. Their data are shown in Figure 4.10 along with the predictions computed.…”

“…For the first two Vleeshouwers [1993] and Vleeshouwers and Nies [1994].) experiments, polystyrene (PS) was used as the example material, allowing comparison with the experimental results [Rehage and Goldbach, 1966;Goldbach and Rehage, 1967;Rehage, 1970;Oels and Rehage, 1977].…”

“…The polymer is assumed to be in equilibrium at the initial temperature T 0 , and then at time t = 0, the temperature is suddenly stepped to the final temperature T 1 . The data of Rehage and Goldbach [Rehage and Goldbach, 1966;Goldbach and Rehage, 1967] are shown in Figure 4.9 for steps from various initial temperatures, T 0 , to the final temperature, T 1 , of 90.70 • C. The thermally polymerized PS examined had a number-average molecular weight of 500 kg/mol. The results basically agree with those of Kovacs [1958], Hozumi et al [1970], Uchidoi et al [1978], and Adachi and Kotaka [1982].…”

“…The computation of volume recovery following pressure steps at constant temperature is analogous to that described above for temperature steps under constant Robertson et al [1985]; data from Rehage and Goldbach [1966] and Goldbach and Rehage [1967].) pressure.…”

“…Lacking the usual S-shape slowdown as equilibrium is reached, however, the recovery from the pressure steps appears to be complete at nearly the same time as that from the temperature steps. Robertson et al [1985]; data from Rehage and Goldbach [1966] and Goldbach and Rehage [1967]. )…”