Electron Spin Resonance Studies of Radicals Formed in Irradiated Polytetrafluoroethylene

Abstract

Radicals formed in irradiated PTFE were studied by means of ESR, using reactions with gases. In interpreting the experimental results, it was assumed that the radicals formed in PTFE primarily by irradiation were —CF2–ĊF–CF2— and —CF2–CF2·. The former were found to be stable, but the latter to be very reactive, at room temperature. A large part of the latter is thought to disappear by recombination, and only a small part to be oxidized by oxygen occluded in the polymer to form less reactive oxide radicals —CF2–CF2–O· even in a vacuum vessel. The radicals —CF2–ĊF–CF2— give a double quintet and —CF2–CF2–O·, a triplet in the spectrum. When gaseous oxygen was admitted to the irradiated PTFE, oxygenated radicals were formed. They will be —CF2–(CF–OO·)–CF2— and —CF2–CF2–OO·; the former giving asymmetrical signal termed OI, and the latter a singlet OII. The following reversible reactions were also studied: —CF2–ĊF–CF2—+O2⇌—CF 2–(CF–OO·)–CF2—, and —CF2–CF–CF2—+NO⇌—CF2– (CF–NO)–CF2. Some discussions are given on the reactions between irradiated PTFE and gases.