ESR STUDY ON FREE-RADICALS TRAPPED IN CROSS-LINKED POLYTETRAFLUOROETHYLENE (PTFE)

Free radicals in crosslinked PTFE which formed by Co-60 gamma-rays irr adiation at 77 K and at room temperature were studied by electron spin resonance (ESR) spectroscopy. The crosslinked PTFE specimens with dif ferent crosslinking density were prepared by electron beam irradiation ih the molten state. The ESR spectra observed in the irradiated cross linked PTFE are much different from those in non-crosslinked PTFE (vir gin); a broad singlet component increases with increasing the crosslin king density, G-value of radicals is much higher in crosslinked PTFE t han in non-crosslinked one. Free radicals related to the broad compone nt are trapped in the non-crystalline region of crosslinked PTFE and r ather stable at room temperature, whereas radicals trapped in amorphou s non-crosslinked PTFE are unstable at room temperature. It is thought that most of free radicals trapped in the crosslinked PTFE are formed in the crosslinked amorphous region. The trapped radicals decays arou nd 383 K (110 degrees C) due to the molecular motion of alpha-relaxati on. (C) 1997 Elsevier Science Ltd.