Changes in the chemical structure of polytetrafluoroethylene induced by electron beam irradiation in the molten state

Polytetrafluoroethylene (PTFE) was exposed to electron beam radiation at el evated temperature above the melting point under nitrogen atmosphere and in vacuum for comparison. Fourier-transform infrared (FTIR) spectroscopy was used to study the changes in the chemical structure. The irradiation under nitrogen atmosphere leads to the same structures as described recently for PTFE irradiated in vacuum. Trifluoromethyl branches and double bond structu res were detected. The concentrations of terminal and internal double bonds are higher after irradiation under nitrogen than in vacuum. Annealing expe riments have shown that the thermal oxidative stability of the radiation-mo dified PTFE is reduced compared to unirradiated PTFE. The reason are the fo rmation of unstable structures such as double bonds. (C) 2000 Elsevier Scie nce Ltd. All rights reserved.