Dependence of the zero shear-rate viscosity and the viscosity function of linear high-density polyethylenes on the mass-average molar mass and polydispersity

被引:0
作者
Florian J. Stadler
Christian Piel
Joachim Kaschta
Sascha Rulhoff
Walter Kaminsky
Helmut Münstedt
机构
[1] Friedrich-Alexander-University Erlangen-Nürnberg,Institute of Polymer Materials
[2] University of Hamburg,Institute of Technical and Macromolecular Chemistry
来源
Rheologica Acta | 2006年 / 45卷
关键词
High-density polyethylene; Zero shear-rate viscosity; Mass-average molar mass; Polydispersity; Viscosity function; Carreau–Yasuda model;
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摘要
Linear high-density polyethylenes with molar masses Mw between 240 and 1,000,000 g/mol, obtained by metallocene catalysts, were characterized in shear using oscillatory and creep tests. The polydispersities of the molar mass distributions (MMDs) lay between 1 and 16. The resulting zero shear-rate viscosities η0 covered a range from 2.5×10−3 to around 108 Pas. Above a critical molar mass of Mc≈2,900 g/mol, the experimental results can be described by the relation η0 ∼ Mw3.6, independently of the MMD. The oscillatory data were fitted with a Carreau–Yasuda equation. The resulting parameters were correlated to molecular structure. The parameter a, being a quantity for the width of the transition between the Newtonian and the non-Newtonian regime, showed a dependence on the molar mass Mw but not on Mw/Mn. The parameter λ of the Carreau-Yasuda equation was found to be the reciprocal crossover frequency for all samples with a log-Gaussian MMD. λ depends on the molar mass Mw and also on Mw/Mn.
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页码:755 / 764
页数:9
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