A method of rapid determination of thermal expansion and apparent second‐order transition temperature of polymer films

An Instron tensile tester has been modified to measure the thermal expansion of polymer films. The method greatly simplifies the experimental procedure necessary for the standard ASTM dilatometric thermal expansion measurement, particularly for thin films. Thermal expansion measurements were made for films of polyester, polycarbonates, vinyls, cellulosies, and polyolefins from room temperature up to 300°F. Second‐order transition temperatures were determined by plotting thermal elongation vs temperature; the transition temperature is indicated by a change in slope. Both expansion coeffcients and transition temperatures as determined by this method give excellent agreement with values reported in the literature.