Modeling of High-pressure Ethene Copolymerizations

The analysis of copolymer composition in Section 4.6.4.1 has been carried out using the terminal model which assumes that radical reactivity is solely determined by the terminal unit on the free-radical chain. The terminal model has been successfully applied to represent the monomer and copolymer compositions for a wide variety of systems, mostly studied at ambient pressure. This model is, however, not capable of describing both copolymer composition and copolymerization kinetics with a single set of reactivity ratios [63]. 

The majority of copolymerization systems studied so far can by represented well by the implicit penultimate unit effect (IPUE) model, where the two radical reactivity ratios, Si = kau/km and S2 - ki22/ 222. are introduced as additional parameters, to account for the influence of the penultimate unit on homopropagation. Within the IPUE model, no penultimate unit effect is considered for the reactivity ratios r = r2i and r2i = rx2- Despite the remarkable 

It should be noted that Predici simulation of kinetics and of polymer properties is extremely valuable for fitting measured copolymerization data and for extracting the full information contained within the experimental data. Moreover, Predici simulation effectively supports attempts to identify reaction conditions that are best suited to the unambiguous and sensitive determination of kinetic parameters [67]. 

Ethene copolymerizations have been thoroughly studied during recent years. A lot of work remains to be done in this area, however, in particular on termination and chain-transfer processes. The progress in these investigations is correlated to improvements achieved in the quality of copolymer MWD analysis. 

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