Effect of pressure on the dielectric γ-relaxation in poly(tetrafluoroethylene) and FEP

• Published in: Macromolecules Vol. 25; no. 26; pp. 7145 - 7149
• Main Authors: Starkweather, Howard W, Avakian, Peter, Fontanella, John J, Wintersgill, Mary C
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.12.1992
• Subjects: Applied sciences; Electrical, magnetic and optical properties; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Tetrafluoroethylene copolymer; Pressure effect; Hexafluoropropylene copolymer; Tetrafluoroethylene polymer; Gamma relaxation; Experimental study; Activation energy; Dielectric relaxation
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma00052a011

Dielectric measurements have been made on PTFE at temperatures from 188-237K and pressures up to 3000 atm. With increasing pressure, internal motions are restricted due to decreases in volume, and the gamma -relaxation shifts to higher temperatures and lower frequencies with an increasing Arrhenius activation energy. The activation volume decreases with increasing temperature but is larger than for the analogous relaxation in polyethylene. The distribution of Helmholtz activation free energies is independent of pressure. In FEP, the copolymer of tetrafluoroethylene and hexafluoropropylene, the loss peak is thought to be a composite of the gamma - and beta -relations.