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

Abstract

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 À1, 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.

A comparative study of characteristics of polytetrafluoroethylene fibers manufactured by various processes

“…It is clear that the four dispersion powders show the same absorption intensity [Figure (a)] that corresponds to two strong peaks (at 1151and 1210cm −1 ). These peaks could be attributed to the E1 or A2 symmetric stretching vibration of the molecular chains of CF 2 chemical bonds . From the spectra, it is reasonable to conclude that the chemical composition of four PTFE powder samples have no significant difference, implying that virgin dispersion powders do not contain extra chemical reagent.…”

Sintering process investigation during polytetrafluoroethylene hollow fibre membrane fabrication by extrusion method

“…Owing to better fusion of PTFE particles in node area, it was more difficult to pull the FCCs out of the node with elevated T S and t S . Furthermore, new fibril formation was suppressed due to the more restrained chain movement in rigid particle 38 because the large-size folded-ribbon-like crystalline structure gradually disappeared during sintering. This may explain the change of mechanical properties of membrane sintered above melting point.…”

Nitroxide-Mediated Controlled Radical Copolymerization of α-Trifluoromethylstyrenes with Styrenes

“…Fluorinated polymers are important materials in everyday life because of their unique properties, such as heat resistance, water repellency, and low dielectric constant [ 1 , 2 , 3 , 4 ]; however, well-established fluoropolymers, such as polytetrafluoroethylene, poly(vinylidenedifluoride), and poly(chlorotrifluoroethylene) are prepared from fluorinated olefin monomers that are gaseous, pose severe safety concerns [ 5 , 6 ], and are difficult to polymerize in an ordinary laboratory. Most of these polymers have very high melting points and poor solubility in common solvents and they lack formability [ 7 , 8 ]. Therefore, (semi)fluorinated polymers using fluorine-containing monomers, which are easy to handle, have recently attracted considerable attention [ 9 ].…”