Melting and Recrystallization Behavior of Polytetrafluoroethylene

Abstract

To clarify the structure of polytetrafluoroethylene (PTFE), a raw film made by compressing and rolling PTFE dispersion particles was examined using thermal analysis, X-ray diffraction and electron microscopy. In the PTFE raw film, granular PTFE particles are in contact with one another; wide angle X-ray diffraction shows their orientation. This orientation diminishes during sintering, but a clearer orientation reappears by cooling. The band structure with striations aligned parallel to the rolled direction appears on the fracture surface for samples prepared at low cooling rates. As the sintering time becomes longer, the oriented structure changes into an unoriented structure. Thermomechanical analysis shows that the PTFE maintains its ‘memories’ of before it was sintered, even in the melt, for a long time. To clear the ‘memories’ thoroughly, sintering at 450°C, or at 370°C for a longer time than 2hrs is necessary for the raw film. © 1983, The Society of Polymer Science, Japan. All rights reserved.