Change of molecular motion of polytetrafluoroethylene (PTFE) by radiation induced crosslinking

The mechanical relaxation of radiation crosslinked PTFE was investigated in conjunction with molecular motion by means of dynamic visco-elastic property measurement in a temperature range from -150 to 350 degrees C under vacuum. The molecular motion is very much affected by crosslinking, that is, the logarithmic decrement of beta relaxation (19 and 30 degrees C) quickly disappears, the gamma relaxation (-97 degrees C) shifts to a higher temperature and alpha relaxation (130 degrees C) shifts to a lower temperature, as the crosslinking density increases. The gamma relaxation is assigned to be a glass transition temperature and the alpha relaxation to be the transition in molecular motion of inter-polymer chains among either crystallites or crosslinking sites. (C) 1997 Elsevier Science Ltd.