EFFECT OF IONIZING-RADIATION ON THE CHEMICAL-COMPOSITION, CRYSTALLINE CONTENT AND STRUCTURE, AND FLOW PROPERTIES OF POLYTETRAFLUOROETHYLENE

In the reported experiments, irradiations that have been conducted in the presence of oxygen, caused acid fluoride end groups to be formed, which on exposure to water vapor hydrolyzed to form carboxylic acid end groups. Analyses by infrared (IR) spectroscopy indicate that when irradiated in a vacuum PTFE exhibits defect absorption bands which have been attributed to branch and crosslink formation. The crystalline content of PTFE which increases after exposure to radiation was monitored by IR spectroscopy, density, x-ray diffraction on unoriented samples, and differential scanning calorimetry (DSC) as the measurement probes. The melt viscosity of PTFE exposed to various radiation doses in air decreases dramatically after irradiation. Between 2. 5 and 5 Mrd an increase in viscosity is attributed to the formation of branches and crosslinks. The effects of preirradiation crystallinity and postirradiation heat treatment were studied. A model is presented to explain the mechanism of the observed radiation effects.