Effect of ionizing radiation on the chemical composition, crystalline content and structure, and flow properties of polytetrafluoroethylene

Abstract

This article describes a study of ionizing radiation‐induced changes in the chemical composition, crystalline content and structure, and flow properties in polytetrafluoroethylene (PTFE). Irradiatins conducted in the presence of oxygen cause acid fluoride end groups to be formed, which on exposure to water vapor hydrolyze 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.

Structural and Physical Properties of Biofield Treated Thymol and Menthol

“…It is postulated that biofield energy may be acted at atomic level in the treated thymol and induced perfect arrangement in the crystals that caused alteration in crystallinity. It was previously reported that high energy radiation treatment appreciably increases the crystallinity in polyethylene and polytetrafluoroethylene [37][38][39]. Similarly, in the present work biofield energy might be acted as a cross linker in thymol and led the formation of crystalline entanglements which enhanced the crystallinity.…”

Modification of PTFE nanopowder by controlled electron beam irradiation: A useful approach for the development of PTFE coupled EPDM compounds

“…Besides these peroxy radicals, carbonyl fluoride groups are also formed which hydrolyse in the presence of atmospheric moisture to form carboxylic acid groups (-COOH). The complete reaction mechanism can be found in [33]. Chemical changes introduced in PTFE after exposure to electron treatment were monitored by FTIR spectroscopy.…”

157-nm pellicles for photolithography: mechanistic investigation of the deep-UV photolysis of fluorocarbons

“…A search for photoproducts of perfluoro-2H-3-oxa-heptane (3) produced upon UV irradiation was made using FTIR, 1 H NMR, 19 F NMR, GC, and GC/MS techniques. Two characteristic bands were observed from FTIR analysis of the photoproducts of 3 upon irradiation at both 254 nm and 185 nm under an air-saturated condition, as shown in spectrum d of Figure 2.…”

“…F NMR measurements. CFCl 3 was employed as an internal reference and calibrated as 0 ppm for the 19 F NMR experiments. The gas chromatography (GC) analyses were performed on a Varian 3900 gas chromatograph using a Varian Facter 4 capillary column or a WCOT fused silica column coating with CP-Sil 5 CB LOW BLEED/MS (25 m x 0.25 mm).…”