Polymer Engineering and Science, Vol.39, No.2, 327-339, 1999
Extrusion characteristics of thermoplastic melts containing fluoropolymers
This paper investigates the influence of fluoropolymers on the extrusion characteristics of three different thermoplastic melts, The presence of a small amount of fluoropolymer reduced the pressure drops, extrudate swell, and retarded the onset of surface defects in linear low density polyethylene (LLDPE), while little or no effect was found in polystyrene (PS) and polyamide 12 (PA 12). Among the fluoropolymers investigated in this study, vinylidene fluoride-hexafluoropropylene (VDF-HFP) copolymer was the most effective additive in reducing the pressure drop and extrudate distortion of LLDPE, polyvinylidene fluoride (PVDF) intermediate, and tetrafluoroethylene-hexafluoropropylene (TFE-HFP) copolymer exhibited the least effectiveness. Contact angle measurements on the die surface indicated that all fluoropolymers preferentially deposit on the die surfaces during the extrusion of LLDPE and PS blends with small amounts of fluoropolymers.