Flow property at capillary extrusion for ethylene–tetrafluoroethylene copolymer

•Melt fracture of ethylene–tetrafluoroethylene copolymer is revealed.•Super-extrusion occurs, leading to high out-put rate extrusion.•Critical stresses of shark-skin and slip-stick failures are found.

The capillary extrusion property of ethylene–tetrafluoroethylene copolymer (ETFE) is evaluated. It is found that ETFE shows several types of flow instabilities. The shark-skin failure is observed over the first critical shear stress 7.9 × 104 Pa. Then, the slip-stick instability is detected at 1.8 × 105 Pa, which corresponds to the critical stress of the slippage at the die wall, evaluated by the Mooney method. Moreover, gross wavy melt fracture appears at high out-put rate condition. It is interesting to note that quasi-stable flow region; so-called “super-extrusion”, is observed between slip-stick and wavy melt fracture regions. Because of the steady slippage, ETFE can be extruded at a high out-put rate condition without surface roughness and distortion of extrudates.

Graphical abstract“Super-extrusion” is observed between slip-stick and wavy melt fracture regions, leading to a high out-put rate extrusion without surface roughness and distortion of extrudates.Figure optionsDownload full-size imageDownload as PowerPoint slide