Metallocene-catalyzed ethene polymerization : long-chain branched polyethene

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en Kokko, Esa 2012-02-10T09:32:49Z 2012-02-10T09:32:49Z 2002-09-06
dc.identifier.isbn 951-22-6080-8
dc.identifier.issn 1239-0518
dc.description.abstract Long-chain branches and narrow molecular weight distribution is a novel structure combination in polyethene, which has only been possible to achieve with single-center catalysis. Long-chain branches, even at very low concentrations, have a strong effect on the polymer melt behavior and, thereby, the processing properties. This work deals with ethene polymerization using group IV metallocene catalysts and the examination of long-chain branching in polyethene. Long-chain branching in metallocene catalysis is believed to take place via a copolymerization route, in which a vinyl terminated polyethene chain is incorporated into a growing polymer chain. Understanding the chain transfer mechanisms (vinyl end-group formation) and copolymerization abilities of metallocene catalysts have been important issues in this work. The examination of the polymerization behavior of several metallocene compounds revealed that chain transfer mechanisms were catalyst specific. Depending on the catalyst structure, the termination of chain growth occurred via β-H elimination, chain transfer to the monomer, or chain transfer to the cocatalyst. The vinyl selectivities were between 20 and 100%. Comonomer response in ethene and 1-olefin copolymerization also depended on the catalyst structure. 10-fold differences in comonomer reactivity ratios were observed. Long-chain branching analysis of homopolyethenes produced with different metallocene catalysts indicated that the catalysts with high vinyl selectivity and good copolymerization ability were the most prominent in producing a polymer with modified rheological properties. In addition to rheological measurements, 13C NMR spectroscopy also showed the presence of long-chain branches. Besides the choice of catalyst, the polymerization conditions had a major impact on long-chain branch contents. Adjusting the ethene, hydrogen, or comonomer (1-olefin or nonconjugated α,ω-diene) concentration changed the rheological properties of the polymers. en
dc.format.extent 52, [98]
dc.format.mimetype application/pdf
dc.language.iso en en
dc.publisher Helsinki University of Technology en
dc.publisher Teknillinen korkeakoulu fi
dc.relation.ispartofseries Acta polytechnica Scandinavica. Ch, Chemical technology series en
dc.relation.ispartofseries 290 en
dc.relation.haspart Malmberg, A., Kokko, E., Lehmus, P., Löfgren, B., Seppälä, J.V., Long-Chain Branched Polyethene Polymerized by Metallocene Catalysts Et[Ind]<sub>2</sub>ZrCl<sub>2</sub>/MAO and Et[IndH4]<sub>2</sub>ZrCl<sub>2</sub>/MAO, Macromolecules 31 (1998) 8448-8454.
dc.relation.haspart Lehmus, P., Kokko, E., Härkki, O., Leino, R., Luttikhedde, H.J.G., Näsman, J.H., Seppälä, J.V., Homo- and Copolymerization of Ethylene and alpha-Olefins over 1- and 2-Siloxy-Substituted Ethylenebis(indenyl)zirconium and Ethylenebis(tetrahydroindenyl)-zirconium Dichlorides, Macromolecules 32 (1999) 3547-3552.
dc.relation.haspart Kokko, E., Malmberg, A., Lehmus, P., Löfgren, B., Seppälä, J. Influence of the Catalyst and Polymerization Conditions on the Long-Chain Branching of Metallocene-Catalyzed Polyethenes, J. Polym. Sci. Part A: Polym. Chem. 38 (2000) 376-388.
dc.relation.haspart Kokko, E., Lehmus, P., Leino, R., Luttikhedde, H.J.G., Ekholm, P., Näsman, J.H., Seppälä, J.V., meso- and rac-Diastereomers of 1- and 2-tert-Butyldimethylsiloxy Substituted Ethylenebis(indenyl)zirconium Dichlorides for Formation of Short- and Long-Chain Branched Polyethene, Macromolecules 33 (2000) 9200-9204.
dc.relation.haspart Kokko, E., Lehmus, P., Malmberg, A., Löfgren, B., Seppälä, J., Long-Chain Branched Polyethene via Metallocene-Catalysis: Comparison of Catalysts. In Organometallic Catalyst and Olefin Polymerization, Catalysts for a New Millennium, Blom, R., Follestad, A., Rytter, E., Tilset, M., Ystenes, M (Eds.) Springer, 2001, 335-345.
dc.relation.haspart Kokko, E., Pietikäinen, P., Koivunen, J., Seppälä, J.V., Long-Chain-Branched Polyethene by the Copolymerization of Ethene and Nonconjugated α,ω-Dienes. J. Polym. Sci. Part A: Polym. Chem. 39 (2001) 3805-3817.
dc.relation.haspart Kokko, E., Wang, W.-J., Zhu, S., Seppälä, J.V., Structural Analysis of Polyethene Prepared with rac-Dimethylsilylbis(indenyl)zirconium Dichloride/Methylaluminoxane in High-Temperature Continuous Stirred-Tank Reactor, J. Polym. Sci. Part A: Polym. Chem. 40 (2002) 3292-3301.
dc.relation.haspart Gabriel, C., Kokko, E., Löfgren, B., Seppälä, J.V., Münstedt, H., Analytical and Rheological Characterization of Long-Chain Branched Metallocene-Catalyzed Ethylene-Homopolymers, Polymer 43 (2002), in press.
dc.subject.other Chemistry en
dc.title Metallocene-catalyzed ethene polymerization : long-chain branched polyethene en
dc.type G5 Artikkeliväitöskirja fi
dc.description.version reviewed en
dc.contributor.department Department of Chemical Technology en
dc.contributor.department Kemian tekniikan osasto fi
dc.subject.keyword metallocene catalysts en
dc.subject.keyword polyethylene en
dc.subject.keyword copolymerization en
dc.subject.keyword characterization en
dc.subject.keyword long-chain branching en
dc.subject.keyword rheology en
dc.identifier.urn urn:nbn:fi:tkk-001871
dc.type.dcmitype text en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.type.ontasot Doctoral dissertation (article-based) en
dc.contributor.lab Laboratory of Polymer Technology en
dc.contributor.lab Polymeeriteknologian laboratorio fi

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