Preparation and characterization of long chain branched polypropylene mediated by different heteroaromatic ring derivatives

Three different heteroaromatic ring derivatives (coagents) were used to adjust the melt radical reaction of polypropylene (PP). From the results of high temperature H-1 NMR and high-temperature size-exclusion chromatography (HT-SEC), all the coagents could quickly convert the tertiary PP macroradicals into resonance stabilized macroradicals and effectively restrain the beta-scission of PP macroradicals. Long chain branched structures, without significant bimodal distribution of molecular weight, could be introduced into coagents-functionalized PP samples. Effect of chemical structures of heteroaromatic rings and electron-attracting groups on the molecular structures and melt properties of modified PP samples was studied. The possible reactions of coagents-functionalized PP samples in different theoretical molar ratio of coagent to alkoxy radical were also proposed according to the results of H-1 NMR, torque curves, rheological measurements and HT-SEC coupled with laser light scattering detector. (C) 2012 Elsevier Ltd. All rights reserved.