Premium
Nonisothermal, uncontrolled homo‐ and copolymerization of ethylene using selected zirconocenes
Author(s) -
Atiqullah Muhammad,
Hammawa Hassan,
Akhtar Muhammad N.,
Khan Javaid H.,
Hamid Halim
Publication year - 1998
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/(sici)1097-4628(19981003)70:1<137::aid-app14>3.0.co;2-4
Subject(s) - branching (polymer chemistry) , crystallinity , copolymer , polymerization , polymer chemistry , ethylene , polymer , thermal stability , materials science , catalysis , diffusion , chain transfer , mixing (physics) , chemical engineering , chemistry , thermodynamics , organic chemistry , radical polymerization , physics , composite material , engineering , quantum mechanics
Nonisothermal, uncontrolled polymerization, conducted in varying mixing regimes, offered a facile methodology to evaluate the influence of several important process development factors such as mixing, reaction exotherm, and thermal perturbations on the catalytic activity and kinetic stability, polymerization performance, and properties of the resulting polymers. Ethylene was homo‐ and copolymerized with hexene‐1 under varying impeller speeds (hence, thermal perturbations), using Ind 2 ZrCl 2 and Et(Ind) 2 ZrCl 2 and the MAO cocatalyst. With respect to the effects of the above process development factors, the following was observed: The reaction exotherm profiles, tracing the polymerization history, qualitatively represented the kinetic profile and the catalytic stability. The unbridged Ind 2 ZrCl 2 was shown to be more stable than the bridged Et(Ind) 2 ZrCl 2 . With change in the level of stirring from a diffusion‐controlled regime to a nondiffusion‐controlled, external gas–liquid mass‐transfer resistance‐free one, the reaction exotherm and the run time‐average catalytic activity increased. So far as the influence of the chiral versus the achiral zirconocene structure is concerned, the copolymer composition distribution and soluble fraction generated by chiral Et(Ind) 2 ZrCl 2 were more sensitive to the mixing conditions and thermal perturbations than were those produced by achiral Ind 2 ZrCl 2 . Et(Ind) 2 ZrCl 2 produced higher molecular weight backbones, incorporated more hexene‐1 and chain branching, and introduced less crystallinity in the copolymers than did Ind 2 ZrCl 2 . The influence of Ind 2 ZrCl 2 on higher‐weight homopolymer backbones was opposite to that of Et(Ind) 2 ZrCl 2 . Incorporation of hexene‐1 significantly decreased the average molecular weights and density and increased the run‐time‐dependent average catalyst activity. A positive comonomer effect took place. The bulk polymer properties did not critically depend on the mixing state. Thermal perturbations broadened the polydispersity index. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 137–147, 1998