Short and long chain branching of polyethene prepared by means of ethene copolymerization with 1-eicosene using MAO activated Me2Si(Me4Cp)(NtBu)TiCl2

Autor: Christian Friedrich, Stefan Trinkle, Rolf Mülhaupt, Dietmar Mäder, Philipp Walter, Jürgen Suhm
Rok vydání: 2000
Předmět:
Zdroj: Macromolecular Chemistry and Physics. 201:604-612
ISSN: 1521-3935
1022-1352
DOI: 10.1002/(sici)1521-3935(20000301)201:5<604::aid-macp604>3.0.co;2-i
Popis: Ethene copolymers with 1-eicosene were prepared using the methylaluminoxane (MAO) activated dimethylsilanediyl (tetracyclopentadienyl) (ter-butylamido)- titanium dichloride (Me 2 Si(Me 4 Cp)(N t Bu)TiC1 2 , CBT) catalyst system in slurry polymerizations. The thermal behavior of the polymers was studied by differential scanning calorimetric (DSC) measurements in order to investigate the influence of long alkyl-branches on polyethene crystallinity, Upon increasing the incorporation of 1-eicosene from 0 to 50 wt.-%, the melting temperature decreased from 135°C to 35°C. The presence of a second peak in the DSC curves of ethene/1-eicosene copolymers with an incorporation of 1-eincosene exceeding 39 wt.-% was attributed to side chain crystallization. CBT is well known for introducing long chain branches (LCB) into polythene. Accordingly, the presence of additional long hain branches (with a chain length of more than 100 carbon atoms) was detected using rheological measurements. In oscillatory and creep tests, samples with low incorporation of 1-eicosene showed a behavior typical of long chain branched polymers. Poly (ethene-co-1-eicosene)s with high incorporation of 1-eicosene behaved like linear polymers, whereas ethene homopolymers contained less LCB. A long chain branching index (BI) was defined using terminal relaxation times. A correlation between BI and 1-eicosene content in the feed, as well as the number of long chain branches was established.
Databáze: OpenAIRE
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