Low Temperature Izod Impact Studies of Blends Based on Impact Grade Polypropylene and Ethylene-α-Octene Copolymer

Abstract

With an aim to enhance low temperature impact strength, blends of PP-cp (Impact Grade PP) and metallocene-catalyzed plastomer (EXACT® ethylene-α-octene copolymer) were prepared using a co-rotating, intermeshing twin-screw extruder in 90 : 10, 80 : 20, 70 : 30, and 60 : 40 weight ratio. Rheological properties studied by Haake’ single-screw extruder with torque rheometer attachment and capillary die showed pseudoplastic melt behavior at 220°C in the shear rate range of 400—4000 s—1. Density and MFI determinations showed minimal change. Morphology studied by low voltage scanning electron microscope (LVSEM) of blend samples showed distinct biphasic blend morphology wherein PP-cp as continuous phase and plastomer as spherical domains (0.5—2 μm size) with stabilized distribution and dispersion. Izod impact strength of the blends at varied temperatures (23, 0, -10, -20, -30, and -40°C) showed substantial enhancement in low temperature impact strength compared to the base polymer (from 44 J/m in case of pure PP-cp to 539 J/m in case of 40% plastomer blend at -40°C).