THERMODYNAMIC PROPERTIES OF PERFLUORINATED LINEAR ALKANES AND POLY(TETRAFLUOROETHYLENES) MEASURED BY PVT AND THERMAL-ANALYSIS

Pressure-volume-temperature data have been obtained for an extensive series of poly(tetrafluoroethylenes) (PTFEs) and PTFE oligomers. The variation of density with MW of the PTFEs is governed by chain end effects, and the results are comparable to the hydrogenated linear alkane series. Dilatometry data of the melting transition in PTFE and oligomers are compared with DSC data on the same samples showing that the premelting region can be characterized in a consistent manner by the two techniques. For three ''high'' MW PTFE samples, crystallinities were determined by ambient densities of the solids, and also by DSC heats of fusion. From the Clapeyron equation and the measured pressure dependence of the melting points and changes in volume upon melting, the heats of fusion of the fully crystalline oligomers and polymers were estimated.