Temperature dependence of the free volume in polytetrafluoroethylene studied by positron annihilation spectroscopy

The temperature dependence of the free volume holes in pure polytetrafluoroethylene (PTFE) and doped with 25% glass have been studied in the temperature range (30-250 degrees C) using positron annihilation lifetime spectroscopy. The data clearly revealed the glass transition temperatures for pure and doped PTFE are 130 and 110 degrees C, respectively. As the temperature increases, the free volume distribution becomes positioned at larger free volume hole size. A good correlation between the electrical conductivity and the o-Ps parameters was achieved. (c) 2006 Elsevier Ltd. All rights reserved.