Change in the porosity of polytetrafluoroethylene during radiation modification above the melting temperature

Abstract

The X ray degree of crystallinity, χ, and the density, ρ, of suspension polymerized polytetrafluo roethylene after its irradiation above the melting temperature of the crystalline phase are studied. A compar ison of dose dependences of χ and ρ makes it possible to infer that pores occur in the initial polytetrafluoro ethylene and that porosity substantially decreases during irradiation. The time of pore contraction in polytet rafluoroethylene after its radiation modification above the meting temperature is estimated with respect to the order of the magnitude. This estimate is based on the consideration of viscous flow under the action of sur face tension forces.

Structure of Polytetrafluoroethylene Modified by the Combined Action of γ-Radiation and High Temperatures

“…Previously, the analysis of the closed pore system in PTFE was carried out by the method of hydrostatic weighing or by measuring the overall dimensions of the samples before or after annealing [32][33][34][35]. Attempts to use scanning electron microscopy methods [33,36] to estimate the size of pores and to analyze the spectral shape of the diffraction maximum hkl = 100 in X-ray spectra of PTFE by the Rietveld method [37,38] are known also.…”