SOLID-STATE EXTRUSION OF VINYLIDENE FLUORIDE (VF2) VINYLIDENE TRIFLUORIDE (VF3) COPOLYMERS .1. DYNAMICS OF SOLID-STATE EXTRUSION

Solid state extrusion dynamics of poly(vinylidene fluoride) and its co polymers have been studied using an Instron capillary rheometer with s pecially designed die set. At and above the Curie transition temperatu res, the copolymers rapidly soften while preserving the semicrystallin e structure. This allows them to be solid state extruded between this temperature and melting temperature. The processing windows within whi ch high quality extrudates can be obtained were established for two co polymer compositions and they were found to be much wider than those t ypically observed in semicrystalline homopolymers such as polyethylene and polypropylene. Extrudate swell under all solid state extrusion co ndition remains constant and is always less than 1 and it was found to increase above this value as the extrusion temperature increased thro ugh the melting region which is typical of melt extrusion of these pol ymers.