Rheological study on tetrafluoroethylene/hexafluoropropylene copolymer and its implication for processability

Abstract

Tetrafluoroethylene/hexafluoropropylene copolymers (FEPs) are widely used in diverse fields due to their outstanding performances in chemical resistance, thermal stability, and insulation. However, their processsability is poor, exhibiting narrow stable flow region and remarkably early melt fracture. Herein, we tried to explore the origin of such poor processability in a rheological way, because melt rheology behaviors are highly related to their processing processes. The shear rheology results indicate that FEPs exhibit multiple flow regions. The flow curve of FEP608 was obtained, and its g 0 value was calculated to be 1.70 kPa s À1 at 360 C. Extensional rheological data suggest that FEPs have much lower e and B values when compared with those of common polymers, suggesting their weaker elasticity during extrusion. Based on such rheological results, the poor processability of FEPs is ascribed to their high viscosity induced by special interchain interaction associating with F atom, which can easily cause accumulated elastic energy.

Fluorinated Polymers as Smart Materials for Advanced Biomedical Applications

“…FEP and PFA are obtained from the copolymerization of TFE with HFP and PPVE, respectively. Both polymers show lower molecular weights than PTFE, in particular FEP, and can be easily processed by conventional polymer processing methods due to the resulting lower melt viscosities [ 48 ]. In terms of chemical and weather resistances and electrical properties, FEP and PFA are quite similar to PTFE ( Table 1 ) [ 49 ].…”

Melt rheological properties of ETFE: an attempt to illuminate the fluorine-substitution effect

“…7, which means large elasticity exists in ETFE melt even under low shear rates. When compared to FEP [47] and common polymers [19,21,45,48,49], the die swell ratio of ETFE is more closer to those of common polymers under same shear condition, implying different characteristics between partially fluorinated and perfluorinated polymers.…”