Effect of chain structure on the melt rheology of modified polypropylene

The effect of molecular structure of polypropylene (PP) on the melt rheolog ical properties were investigated for electron irradiated polymer and di-2- ethylhexyl peroxy dicarbonate (EHPC)-treated polymer. The modifications wer e examined in terms of the rheological behaviors, molecular weight distribu tion, and the degree of branching. The high melt strength PP was obtained b y irradiating with 50 and 80 kGy and adding EHPC. The modified PPs showed t he strain hardening in the uniaxial elongational viscosity, though the line ar elongational viscosity was lower than that of the unmodified PP. Low ang le laser light-scattering measurements of the modified PPs showed the inter esting results; high irradiation doses such as 50 and 80 kGy caused higher molecular weight chains branching. Nevertheless, the long branching chains were not detected for the EHPC modified PP, which also showed the strain ha rdening in uniaxial elongational flow. In this article, the relation betwee n chain structure and rheological properties is discussed. (C) 1999 John Wi ley & Sons, Inc.