Melt processability of polytetrafluoroethylene: Effect of melt treatment on tensile deformation mechanism

It is widely accepted that the melt processibility of polytetrafluoroethylene (PTFE) is poor. In this article, a high‐molecular‐weight PTFE was extruded smoothly with a modified die; and critical shear rate could be raised to 4 s^?1, using a die with L/D (length to diameter) ratio of 200. Meanwhile, we compared the current PTFE fiber spinning method with melt spinning to investigate the effects of high‐temperature treatment on the drawability of PTFE and found that the processing sequence could play a key role. The deformation imposed before or after the high‐temperature treatment could determine whether the fibrillation can be achieved continuously and effectively. Based on the experiment phenomenon, together with the results of differential scanning calorimetry, X‐ray diffraction, and scanning electron microscopy characterization, we proposed a model to describe the submicron structural change of PTFE during extension. From this model, the fundamental mechanism for the poor melt processibility of PTFE was elucidated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012