article

Abstract

Long chain branches have been introduced on linear propylene through its modification by reaction with peroxydicarbonates in a twin screw extruder. The melt strength of the modified polymers was determined with a Rheotens apparatus and found to improve to a much greater degree than what the very few branches and the slight increase of the molecular weight would suggest. The zero shear viscosity increased, while the viscosity at the shear thinning range did not change. The elasticity as measured by the extrudate swell, the elastic modulus and the extensional viscosity growth increased. The branched PP samples show distinct strain hardening, something that is absent in the original linear melt.  It seems that even a low degree of long chain branching at high molecular weights is able to enhance the strain hardening behaviour of the PP chains.

j. rheology, 48(4), 895-914, 2004

Effect of long branches on the rheology of polypropylene