Olefin polymerization and copolymerization
Nona Ghasemi Hamedani; Fatemeh Poorsank; Hassan Arabi; Seyed Mehdi Ghafelehbashi
Abstract
Insights have been developed into the influence of different structures, including bismethoxymethylfluorene (B) and 2,2-diisopropyl succinate (I), on both internal donor (ID) and external donor (ED) roles on the performance of MgCl2/ID/TiCl4. Catalyst performance including activity, hydrogen response, ...
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Insights have been developed into the influence of different structures, including bismethoxymethylfluorene (B) and 2,2-diisopropyl succinate (I), on both internal donor (ID) and external donor (ED) roles on the performance of MgCl2/ID/TiCl4. Catalyst performance including activity, hydrogen response, molecular weight distribution and thermal properties is explained through the coordination nature of external donors and its correlation with the internal donor. Replacement of the typical alkoxysilane ED with B and I leads to an overall decrease in activity, which is more pronounced (average 1.4 times) in systems with similar structures as ID and ED. However, these compounds significantly enhance hydrogen response. The use of B as ED leads to an average 1.5-fold increase in MFI and usage of I as ED results in an average 1.1 times increase in MFI. Changing the ED influenced the thermal properties so that in the catalyst with the succinate structure as ID, altering the ED from alkoxysilane to I, leads to an increase in crystallinity from 43.86% to 48.12%. These findings suggest that the choice of package of internal and external donor can significantly influence the resulting polymer characteristics.
Olefin polymerization and copolymerization
Wei Wang; Taoyi Zhang; Liping Hou
Abstract
The present paper systematically studies the homo- and copolymerization of ethylene or propylene using metallocene as catalyst and diethyl zinc as chain transfer agent to obtain the polyolefin waxes with narrow molecular weight distribution and with a high activity. The molecular weight of the resultant ...
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The present paper systematically studies the homo- and copolymerization of ethylene or propylene using metallocene as catalyst and diethyl zinc as chain transfer agent to obtain the polyolefin waxes with narrow molecular weight distribution and with a high activity. The molecular weight of the resultant polymer could be controllable by the concentration of diethyl zinc quantitatively. The introduction of a-olefin into the ethylene polymerization system would shield the chain transfer action, and the shielding effect in propylene (co) polymerization is more serious, due to the mass transfer resistance of the substituents on the monomers. Branched comonomer and long chain comonomer provide stronger shielding effect. The regression results show that the order of the chain transfer reaction of propylene polymerization is smaller than that of ethylene polymerization, and the order of the chain transfer reaction of copolymerization is less than that of homopolymerization. It indicates that the substituent on the monomer would result in the deviation of the regression data from the ideal primary reaction order.
