Clear impact-resistant syndiotactic polypropylene

Abstract

Syndiotactic polypropylene blends having a unique set of mechanical properties may be prepared by blending syndiotactic polypropylene with an ultra low density polyethylene and, optionally, an isotactic polypropylene random copolymer. The syndiotactic polypropylene blends of the present invention have been found to have improved impact strength, reduced haze, increased light transmittance, and reduced flexural modulus. It has been determined that the addition of about 10 to about 50 wt % of an ultra low density polyethylene plastomer to a syndiotactic polypropylene can greatly enhance mechanical toughness, particularly at low temperatures, while maintaining good optical clarity. These results are made possible by using a sPP material with good optical clarity and dispersing the ULDPE plastomer uniformly throughout the sPP matrix to act as a sort of impact modifier. Moreover, the addition of about 10 to about 50 wt % of an iPP random copolymer to the sPP matrix phase provides comparable or improved mechanical properties while also resulting in a significant reduction in injection molding cycle times. The syndiotactic polypropylene blends according to the present invention may be further processed according to accepted practices to make cast films, blown films, co-extruded films, laminated sheets, injection molded parts, blow molded containers, and other articles using basic plastic fabrication techniques as known in the art.