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High molecular weight tail and long-chain branching in low-density polyethylenes



The composition of the high molecular weight tail in branched low-density polyethylenes made by both tubular and autoclave reactors was studied in detail using size-exclusion chromatography (SEC) coupled with a viscosity detector (VD) and a two-angle light-scattering detector (LSD). The detection of a second peak at very small elution volumes in the light-scattering chromatogram but not in the refractive index chromatogram and viscosity chromatogram is due to high molecular weight species. It is also indicative of a change in the long-chain branching distribution. It was found that the intrinsic viscosity contraction factor g′ scales with the radius of the gyration contraction factor, g, with the exponent, ε, having a value in the range 0.4–1.4. Furthermore, ε shows significant molar mass dependence. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2815–2822, 2001