Thermo-Oxidative Degradation of Polypropylene by Use of Screw Extruders

Abstract

Films were cast from a polypropylene thermo-oxidatively degraded by use of a screw extruder and an undegraded polypropylene with a T-die extruder. The effect of casting conditions on the structures and properties of the films were studied.Films cast from the degraded polypropylene show superior transparency, dart impact strength, and heat sealability and show low stiffness and slipperiness. α-crystal phase is decreased and smectic and amorphous phases are increased by degradation. Although such tendency is also attained by decreasing the chill roll temperature or by increasing die temperature, it is more notable in films cast from the degraded polypropylene than in ones cast from the undegraded polypropylene under any casting conditions. Films cast from the degraded polypropylene have a feature that their inner structures are almost constant independent of the casting conditions.