Randomand block copolymerization of ethylene and a-olefins with Ziegler-Natta catalysts
Polimery 1994, No 10, 593
The kinetics of ethylene polymerization and of its successive copolymerization with propylene under varying conditions of comonomer addition into the reaction medium and with changing the comonomer addition sequence has been investigated in the presence of high-active magnesium- supported titanium catalyst. To determine correctly the rate of incorporation of ethylene into copolymer chain and of the ethylene/propylene copolymerization rates it was necessary to determine also the concentration of this monomer in the vicinity of active centre, this concentration being different from that in the polymerization medium because of monomer access to catalyst being limited by the previously formed polymer.Therefore, the solubilities of ethylene and propylene in isotactic polypropylene and in UHMWPE were determined both in the presence and in the absence of a hydrocarbon solvent. The corresponding dissolution rates were determined as a function of temperature.
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