Addition of filled or unfilled fluoropolymers and their effects on the electrification of a metallocene polyethylene during capillary flow

During the extrusion of polymers, the extrudates exhibit distortions at high shear rates such as sharkskin, spurt or gross melt fracture that limit industrial production rates. One solution to reduce or eliminate these defects is to induce slip at the die wall or in the polymer bulk for example by adding some polymer processing additives (PPA).In this study, we used the addition of different fluoropolymers with and without inorganic fillers to promote wall and interlayer slippage in a metallocene polyethylene (mPE). As expected, defects onset was delayed and shear stress was decreased in any case due to the increase of slip velocity.In a previous work, we showed that the electrical charging of the extrudate during the extrusion could be correlated with slip velocity. Present results confirmed the relationship between electrical charging and wall or interlayer slippage. Indeed, the higher the amount of PPA without filler in the melt, the higher the wall-slippage and the higher the electrification. The filled fluoropolymer exhibited a more efficient postponing of extrusion defects than unfilled ones concomitant with a strong increase of the extrudate electrical charging. Finally, electrical charging versus wall-slippage curves witnessed the influence of additives concentration and nature on electrification as expected from the double-layer theory.