Peroxydicarbonate modification of polypropylene and extensional flow properties

Long chain branches (LCB) were added to initially linear polypropylene (PP) using reactive extrusion in the presence of selected organic peroxydicarbo nates (PODIC). The LCB structure was confirmed by high temperature size exc lusion chromatography combined with on-line intrinsic viscosity measurement s. Compared to the initial linear PP, the branched samples showed distinct strain hardening of the elongational viscosity, slightly lower Melt Flow In dex, increased extrudate swelling and improvement of the melt strength by u p to a factor of two. All elastic properties increased with the degree of b ranching. The efficiency of PODIC with varying structure for the LCB modifi cation of PP was evaluated. PODIC with non-linear or large linear alkyl gro ups resulted in modified PP with the highest degree of branching and the fa stest strain hardening. (C) 2001 Elsevier Science Ltd. All rights reserved.