Structure-Property Relationships of Linear and Long-Chain Branched Metallocene High-Density Polyethylenes Characterized by Shear Rheology and SEC-MALLS
✍ Scribed by Christian Piel; Florian J. Stadler; Joachim Kaschta; Sascha Rulhoff; Helmut Münstedt; Walter Kaminsky
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 242 KB
- Volume
- 207
- Category
- Article
- ISSN
- 1022-1352
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✦ Synopsis
Abstract
Summary: Linear and long‐chain branched high‐density polyethylenes with a molar mass $\overline M _{\rm w}$ between 1 700 and 1 150 000 g · mol^−1^ were synthesized using metallocene catalyst systems. Depending on the polymerization parameters the molar mass distribution reached values ranging from 2 to 12. The resins were characterized with various analytical methods. The branch detection took place via two independent methods, melt rheology and SEC‐MALLS. New relationships between catalyst structure, polymerization conditions, and the branching content of polyethylenes were established. Besides the branched materials strictly linear polymers are presented; for those no long‐chain branches were detected either by light scattering or by rheology. The viscosity function was observed to be strongly influenced by the molar mass distribution and the degree of long‐chain branching. The molar mass distribution was affected by the catalyst type and the polymerization conditions. A dependence of the melting point and the melting enthalpy on the molar mass was observed.
η~0~‐$\overline M _{\rm w}$ correlation of the linear and long‐chain branched samples.
image__η__~0~‐$\overline M _{\rm w}$ correlation of the linear and long‐chain branched samples.