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Short and long chain branching of polyethene prepared by means of ethene copolymerization with 1‐eicosene using MAO activated Me 2 Si(Me 4 Cp)(N t Bu)TiCl 2
Author(s) -
Walter Philipp,
Trinkle Stefan,
Suhm Jürgen,
Mäder Dietmar,
Friedrich Christian,
Mülhaupt Rolf
Publication year - 2000
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(20000301)201:5<604::aid-macp604>3.0.co;2-i
Subject(s) - branching (polymer chemistry) , copolymer , polymer chemistry , crystallinity , polymer , differential scanning calorimetry , alkyl , methylaluminoxane , chemistry , crystallization , materials science , chemical engineering , polymerization , organic chemistry , crystallography , metallocene , physics , engineering , thermodynamics
Ethene copolymers with 1‐eicosene were prepared using the methylaluminoxane (MAO) activated dimethylsilanediyl(tetracyclopentadienyl) (tert ‐butylamido)‐titanium dichloride (Me 2 Si(Me 4 Cp)(N t Bu)TiCl 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‐eicosene exceeding 39 wt.‐% was attributed to side chain crystallization. CBT is well known for introducing long chain branches (LCB) into polyethene. Accordingly, the presence of additional long chain 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.