STUDY ON ROUGH-SURFACE BIAXIALLY ORIENTED POLYPROPYLENE FILM .1. FORMATION OF BETA-FORM CRYSTALS IN SHEET CAST WITH T-DIE EXTRUDER

Sheets were cast by extruding polypropylenes (PP) which contained gamma -quinacridone, a beta -crystal nucleator, at levels of 0-10 ppm using a 30 mm phi extruder with a T-die at extrusion temperatures of 200-260 degree C and chill roll temperatures of 30-90 degree C. The influences of raw resin characteristics such as gamma -quinacridone content and MFI of the base PP and casting conditions such as extrusion temperature and chill roll temperature on the amount of beta -crystals formed in the sheet were studied. The amount of the beta -crystals formed was larger as the gamma -quinacridone content was higher and the extrusion temperature was lower and almost independent of the chill roll temperature.