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Tailoring Polyethylene Characteristics Using a Combination of Nickel α ‐Diimine and Zirconocene Catalysts under Reactor Blending Conditions
Author(s) -
Mota Fábio F.,
Mauler Raquel S.,
de Souza Roberto F.,
Casagrande, Jr Osvaldo L.
Publication year - 2001
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(20010401)202:7<1016::aid-macp1016>3.0.co;2-n
Subject(s) - methylaluminoxane , polyethylene , differential scanning calorimetry , materials science , gel permeation chromatography , polymerization , linear low density polyethylene , polymer chemistry , zirconium , low density polyethylene , polymer , metallocene , composite material , physics , metallurgy , thermodynamics
Ethylene was polymerized using a combination of Ni( α ‐diimine)Cl 2 ( 1 ) ( α ‐diimine = 1,4‐bis(2,6‐diisopropylphenyl)acenaphthenediimine) and rac ‐ethylenebis(IndH 4 )ZrCl 2 ( 2 ) (IndH 4 = 4,5,6,7‐tetrahydro‐1‐ η 5 ‐indenyl) compounds, activated with methylaluminoxane in toluene. The polymerizations were performed at three different temperatures (0, 30, and 50°C), and the effect of varying the zirconium loading molar fraction ( x Zr ) was monitored. The polymerization runs carried out at 0 and 50°C show that the productivity increases linearly with x Zr . On the other hand, at 30°C the productivity reaches a maximum of 8.19×10 3 kg of PE/mol[M]·h for x Zr = 0.67, indicating a non‐linear correlation between the productivity and x Zr . The polyethylene characteristics have been evaluated by means of differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and scanning electron microscopy (SEM). The PE produced at 0 and 30°C showed monomodal molecular weight distributions with narrow polydispersities. At higher temperature (50°C), using x Zr = 0.10, two different polyethylenes were produced; an amorphous rubbery PE with M̄ w of 83×10 3 g·mol –1 and a linear high density PE with M̄ w of 284×10 3 g·mol –1 . DSC thermograms of the PE obtained at 0°C ( x Zr = 0.25–0.50) showed the presence of two melting points corresponding to branched and linear PE, indicating a low compatibility between the phases. By SEM it was observed that the branched polyethylene obtained at 0°C forms very small aggregates dispersed in the linear polyethylene matrix, but the polymer obtained at 30°C forms larger particles which show low compatibility with the linear polyethylene.