A MODEL FOR PREDICTING SLIP VELOCITY DURING EXTRUSION WITH FLUOROPOLYMER PROCESSING ADDITIVES

A molecular model, based on the concept of the activation rate theory, is developed for slip of a polymer as it flows through a die. The mod el correctly predicts the dependence of the apparent slip velocity of high molecular weight, linear polyethylene resins on wall shear stress , up to the onset of gross melt fracture. It also predicts the increas ed slip which occurs when die surfaces are coated with a fluoropolymer processing aid having a low surface tension.