Effect of absorbed chemicals on the low-temperature dielectric properties of poly(tetrafluoroethylene)

Dielectric measurements were made from 5 to 300 K on poly(tetrafluoroethylene) which had been saturated with chloroform, fluorocarbon-113 (1,1,2-trichloro-1,2,2-trifluoroethane), or carbon tetrachloride. The peak height for the gamma-relaxation was increased by the polar additives. In the case of fluorocarbon-113 at frequencies below 1 kHz, it was shifted to lower temperatures with a lower activation energy. In the presence of either of the polar additives, a new relaxation appeared with a maximum in tan-delta at 1 kHz of 49 K for chloroform and 61 K for fluorocarbon-113 in isothermal frequency scans. These relaxations had activation energies of 2-3 kcal/mol and activation entropies close to zero. They are assigned to the reorientation of the absorbed molecules moving independently of each other. In separate measurements on chloroform and fluorocarbon-113, a relaxation was observed at temperatures below their melting points which became weaker after purification.