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Synthesis and properties of branched polyethylene/high‐density polyethylene blends using a homogeneous binary catalyst system composed of early and late transition metal complexes
Author(s) -
Kunrath Fábio A.,
Mauler Raquel S.,
de Souza Roberto F.,
Casagrande Osvaldo L.
Publication year - 2002
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 - 10.1002/1521-3935(200210)203:14<2058::aid-macp2058>3.0.co;2-#
Subject(s) - polyethylene , homogeneous , polymer chemistry , materials science , catalysis , transition metal , binary number , high density polyethylene , chemical engineering , polymer science , chemistry , composite material , organic chemistry , thermodynamics , engineering , physics , arithmetic , mathematics
Branched polyethylene/high‐density polyethylene blends (BPE/HDPE) with a wide range of molecular weights, melt flow indexes (MFI), and intrinsic viscosity were prepared using the homogeneous binary catalyst system composed by Ni( α ‐diimine)Cl 2 ( 1 ) ( α ‐diimine = 1,4‐bis(2,6‐diisopropylphenyl)‐acenaphthenediimine) and {Tp Ms* }TiCl 3 ( 2 ) (Tp Ms* = hydridobis(3‐mesitylpyrazol‐1‐yl)(5‐mesitylpyrazol‐1‐yl)) activated with MAO and/or TIBA in hexane at two different polymerization temperatures (30 and 55 °C) and by varying the nickel loading molar fraction ( x Ni ). At all temperatures, a non‐linear correlation between the x Ni and the productivity was observed, suggesting the occurrence of a synergistic effect between the nickel and the titanium catalyst precursors, which is more pronounced at 55 °C. The molecular weight of the BPE/HDPE blends considerably decreases with increasing Al/M molar ratio. The melt flow indexes (MFI) and intrinsic viscosities ( η ) are strongly affected by x Ni , but the melting temperatures are nearly constant, 132 ± 3 °C. Dynamic mechanical thermal analysis (DMTA) shows the formation of different polymeric materials where the stiffness varies according to the x Ni and temperature used in the polymerization reaction. The surface morphology of the BPE/HDPE blends studied by scanning electron microscopy (SEM) revealed a low miscibility between the PE phases resulting in the formation of a “sandwich structure” after etching with o ‐xylene.