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

With an aim to enhance low temperature impact strength, blends of PP-cp ( Impact Grade PP) and metallocene-catalyzed plastomer (EXACT (R) ethylene-alpha-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 degrees 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 mu m size) with stabilized distribution and dispersion. Izod impact strength of the blends at varied temperatures ( 23, 0, -10, -20, -30, and -40 degrees 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 degrees C).