THERMAL SHRINKAGE OF STRETCHED POLYVINYLCHLORIDE FILMS

Abstract

In this report the properties of PVC films prepared by various stretching methods is discussed from the point of view the thermal shrinkage under no tension. The test films were prepared by the following four stretching methods: uniaxial stretching under the conditions of free and constant width, and two-way successive and simultaneous biaxial stretching. The stretching was performed in a recirculating hot-air bath. The test of thermal shrinkage for these stretched films was performed in a glycerin bath changing the temperature and time (65°C_??_120°C and 10_??_103.5 sec). The following results were obtained:1. The shrinkage of the films is affected characteristically by the stretching method.2. The isothermal shrinkage curve as the functions of time has a shape similar to the stress-relaxation curve.3. A master curve for the thermal shrinkage can be obtained by means of time-temperature superposition. The inflection point of this curve is a measure of the glass transion point.* Studies on the Biaxially Stretching of Films. Part 2.Presented in the 21st Annual Meeting of the Chemical Society, Japan, Kansai University, Osaka, March 31, 1968.