Synthesis and characterization of ethylene-propylene copolymer and polyethylene using α-diimine nickel catalysts

Pourtaghi-Zahed, Hamid; Zohuri, Gholam
November 2012
Journal of Polymer Research;Nov2012, Vol. 19 Issue 11, p1
Academic Journal
Nickel-based catalysts of dibromo[ N,N′-bis(2,6-diisopropylphenyl)-2,3-butanediimine]nickel(II) ( A) and dibromo[ N,N′-(phenanthrene-9,10-diylidene)bis(2,6-diisopropylaniline)]nickel(II) ( B) were synthesized under controlled conditions. The catalysts A, B and mixed of 1:1 weight ratio of them were used for ethylene-propylene (EP) copolymerization and ethylene polymerization. Methylaluminoxane (MAO) was used as a cocatalyst. The polymers were characterized by means of FT-IR, H NMR and DSC (Differential scanning calorimetry). In ethylene polymerization using mixed of 1:1 w/w of the catalysts A and B degree of branching polymer chain decreased with increasing monomer pressure while increased with enhancing polymerization temperature. In ethylene-propylene copolymerization using mixed of 1:1 w/w of A and B, the catalytic system showed the maximum activity at about [Al]/[Ni] = 2000:1 ratio and further addition of MAO did not affect the activity of the catalyst. Increasing the copolymerization temperature from 20 to 80 °C decreased the productivity of the catalytic system while increased the ethylene content of the copolymer. Decreasing relative pressure of P/P from 9:1 to 1:1 increased the ethylene contents of the copolymers from 51 % to 72 % while decreased the viscosity average molecular weight (M) and glass transition temperature (T) of the products. A copolymer with more rubber-like behavior was obtained in relative pressure of P/P (5:1) and total pressure of 5 bars.


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