Beta Ray Absorption in Polymers and Determination of First and Second-Order Transition Temperatures

It is possible to determine the first- and second-order transition temperatures of polymers, copolymers, and other organic and inorganic substances with good accuracy and reproducibility by measuring their absorption of beta radiation. Variations in the measured absorptions are in essence related to variations in the product of the density and thickness of the sample, so that the method can be employed, in practice, when seeking information concerning variations in density, with the temperature or the time. The technique was used to investigate a number of polymers, e.g., polyethylene terephthalate, polystyrene, polyethylene, 1,4-cis polybutadiene, natural rubber, polyisobutylene, polybutene-1, polypropylene, and certain copolymers of ethylene/propylene and ethylene/butene-1. Finally, data pertaining to phase transitions in organic and inorganic substances are presented. The results are discussed., and compared with those obtained by other methods.