Premium
Ethylene homo‐ and copolymerization over MgCl 2 ‐TiCl 4 catalysts: Polymerization kinetics and polymer particle morphology
Author(s) -
Hassan Nejad Mehdi,
Ferrari Paolo,
Pennini Gianni,
Cecchin Giuliano
Publication year - 2008
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/app.27964
Subject(s) - copolymer , polymer , polymerization , polymer chemistry , materials science , monomer , kinetics , morphology (biology) , particle (ecology) , diffusion , catalysis , ethylene , chemical engineering , chemistry , thermodynamics , composite material , organic chemistry , oceanography , physics , quantum mechanics , biology , engineering , genetics , geology
Three procatalysts of the MgCl 2 /TiCl 4 type, differing mainly in their morphological characteristics, were investigated in ethylene polymerization and ethylene‐1‐butene copolymerization. Apparently, hydrogen has an intrinsic and general deactivating effect but it can also play an activating effect in homopolymerization. This peculiarity was found to be related to a catastrophic breakage of the polymer/catalyst particles during growth and thus to the exposure of new active centers. In this case the kinetic profiles are irregular and characterized by one or more secondary peaks which reflect the moment when this morphology‐driven rate‐enhancement effect takes place. In general, the prepolymerization of the procatalysts with propylene tends to slightly enhance homopolymerization rate, to slow down copolymerization rate and to stabilize the morphology of the growing polymer particles, thus preventing the occurrence of the irregular kinetic profiles observed during homopolymerization in the presence of hydrogen. The behavior of the procatalysts investigated was found to depend on the distribution of their pore size rather than the absolute values of their porosity. Likely this is due to an easier diffusion of the monomer and a more regular and homogeneous growth of the polymer within larger as opposed to smaller pores. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008