Glass transitions in polypropylene

Abstract Dilatometric measurements show that both isotactic and atactic polypropylenes have two distinct glass transition temperatures. Because of the two transitions, three values for the cubical coefficient of thermal expansion are necessary to accurately define the volume expansion of polypropylene from −80° to +90°C. A method is outlined for calculating the content of amorphous atactic, amorphous isotactic, and crystalline isotactic polymer in a given polypropylene sample.