CHANGE OF MOLECULAR-MOTION OF POLYTETRAFLUOROETHYLENE (PTFE) BY RADIATION-INDUCED CROSS-LINKING

The mechanical relaxation of radiation crosslinked PTFE was investigat ed in conjunction with molecular motion by means of dynamic visco-elas tic property measurement in a temperature range from -150 to 350 degre es C under vacuum. The molecular motion is very much affected by cross linking, 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 i nter-polymer chains among either crystallites or crosslinking sites. ( C) 1997 Elsevier Science Ltd.