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The Effect of Reactor Conditions on High‐Impact Polypropylene Properties and Gas Phase Polymerization Kinetics
Author(s) -
Cancelas Aarón J.,
Yang Lanti,
Girod Robin,
de Heer Jos,
Kleppinger Ralf,
Delsman Erik,
Wang Jingbo,
Gahleitner Markus,
Monteil Vincent,
McKenna Timothy F. L.
Publication year - 2018
Publication title -
macromolecular reaction engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.37
H-Index - 32
eISSN - 1862-8338
pISSN - 1862-832X
DOI - 10.1002/mren.201700063
Subject(s) - copolymer , polypropylene , materials science , tacticity , polymer chemistry , polymerization , ethylene , chemical engineering , chain transfer , natural rubber , phase (matter) , molar mass distribution , kinetics , catalysis , polymer , chemistry , composite material , radical polymerization , organic chemistry , physics , quantum mechanics , engineering
High impact polypropylene (hiPP) powders are made in a 2.5 L semi‐batch gas‐phase reactor using a Ziegler–Natta catalyst and two sequential polymerization steps. The amount of copolymer, reactor temperature and pressure, the relative amounts of ethylene and propylene, and the presence of hydrogen are varied systematically to understand their impact on the copolymerization kinetics, hiPP properties, and on rubber distribution. Examples of discoveries are that the presence of hydrogen can reduce copolymerization activity, depending on the catalyst system, and that the fraction of crystalline copolymer decreases with 1) copolymer content in hiPP; and 2) copolymerization activity. The last implies a resistance to mass transfer of ethylene during copolymerization. To understand this phenomenon, atomic force microscopy analyses of hiPP samples with distinct morphology of the polypropylene matrix (isotactic polypropylene, iPP) and copolymer ethylene/propylene ratios are performed after microtoming. It is found that mesoparticles are the determining structure for the copolymer distribution, and that powders with more ethylene in the copolymer or an iPP matrix better suited for mass transfer had more rubber in the center of the mesoparticles. This indicates that the length scales of the mesoparticles that control transfer limitations for ethylene also impact the properties of the final impact copolymer.