Cooperative motions in PVC studied by thermally stimulated currents: Comparison with A.C. dielectric derivative analysis

Abstract

The thermally stimulated current–thermal sampling (TSC–TS) technique was used to study the broadened glass transition in conventional “atactic” poly(vinyl chloride), PVC. The activated parameters obtained from the TSC–TS data, mainly the apparent activation energy (Ea), characterize the breadth of glass transitions in a very sensitive way. These results are compared with those values of Ea obtained from the literature, using a recently proposed method of analyzing a.c. dielectric constants and their derivatives, over the temperature range of −100–130°C. Both techniques detect weak cooperative glass transition‐like relaxations well below the main glass transition of ca. 80°C. As is the case with “atactic” PMMA, the data suggest that compositional heterogeneity related to a small fraction of predominantly isotactic sequences contribute to the broad glass transition extending ca. 60°C below the main glass transition in atactic PVC. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 913–918, 1998

Study of the Effect of Annealing and Physical Aging on PVC by the Thermally Stimulated Currents Methods

“…[8] The plot of logðsÞ ¼ fð1=TÞ, where s is the relaxation time, indicates a compensation phenomenon that demonstrates the existence of an order within the material in its amorphous phase. [9] This compensation phenomenon is observed for each temperature of annealing. An empirical formula is introduced that relates the rate of crystallinity to the temperature of compensation.…”

TSDC spectroscopy of relaxational and interfacial phenomena

“…Nogales and Sauer [269] used the TSDC-thermal sampling (TSDC-TS) technique to study the broadened glass transition in conventional "atactic" poly(vinyl chloride), PVC (Fig. 64).…”

“…350 K. As is the case with "atactic" PMMA, the data suggest that compositional heterogeneity related to a small fraction of predominantly isotactic sequences contribute to the broad glass transition extending ca. 333 K below the main glass transition in atactic PVC [269].…”

Thermally stimulated depolarization current behaviour of 75 MeV oxygen ion irradiated Kapton-H polyimide film

“…In the present article, we are reporting the effect of 75 MeV oxygen ions on the various dielectric relaxation processes in Kapton-H polyimide using the thermally stimulated depolarization current (TSDC) technique. This technique is known for its capability of resolving complex dielectric relaxation processes into narrow distributions of relaxations [11][12][13][14]. The various current maxima appearing in the TSDC spectrum characterize the operative molecular mechanisms through which an electret stores its charge.…”