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Rheologica Acta

, Volume 51, Issue 9, pp 821–840 | Cite as

Detecting very low levels of long-chain branching in metallocene-catalyzed polyethylenes

  • Florian J. Stadler
Original Contribution

Abstract

The detection of long-chain branches (LCBs) is an issue of significant importance in both basic research and industrial applications, as LCBs provide excellent means to improve the processing behavior, especially in elongation-dominated processing operations. In this article, different methods for the detection of very low amounts of LCBs in metallocene-catalyzed polyethylene are presented and compared with respect to their sensitivity. Depending on the molar mass, the zero shear rate viscosity increase factor η 0/\(\eta_{0}^{\rm lin}\), the steady-state elastic recovery compliance \(J_{e}^{0}\), the complex modulus functions G′(ω) and G″(ω), and the thermorheological complexity were found to be sensitive. In general, the higher the molar mass, the more important the transient quantities become and the easier finding the long-chain branches gets. Although rheology is very sensitive, rheological methods in combination with size exclusion chromatography proved to be the most sensitive combination to detect even very low amounts of LCBs. Especially methods involving the elastic properties (G′(ω), \(J_{\rm e}^{0}\), and J r(t)) react very sensitively, but these are also very distinctly influenced by the molar mass distribution.

Keywords

Long-chain-branched metallocene-catalyzed polyethylene Rheology SEC-MALLS Branch detection Zero shear rate viscosity η0 Steady-state elastic recovery compliance \(J_{e}^{0}\) 

Notes

Acknowledgements

The author would like to thank the German Research Foundation for the financial support and Prof. Dr. H. Münstedt, Dr. J. Kaschta, and Mrs. I. Herzer (University Erlangen) for the GPC-MALLS measurements. The authors would also like to acknowledge Dr. Christian Piel, Dr. Burçak Arikan, and Prof. Dr. Walter Kaminsky (University Hamburg) for the synthesis of most of the samples used in this article and Dr. Katja Klimke and Dr. Matthew Parkinson of the Max-Planck Institute of Polymer Research in Mainz (group of M. Wilhelm) for the solid-state NMR measurements. The financial support from “Human Resource Development (201040100660)” of the Korea Institute of Energy Technology Evaluation and Planning and from the National Research Foundation (Rheological Characterization of Intelligent Hydrogels) is gratefully acknowledged.

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© Springer-Verlag 2012

Authors and Affiliations

  1. 1.School of Semiconductor and Chemical EngineeringChonbuk National UniversityJeonbukRepublic of Korea

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