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Copolymer Composition Distribution (copolymer + composition_distribution)
Selected AbstractsOn the Production of Polyolefins with Bimodal Molecular Weight and Copolymer Composition Distributions in Catalytic Gas-Phase Fluidized-Bed ReactorsMACROMOLECULAR THEORY AND SIMULATIONS, Issue 8 2007Christos Chatzidoukas Abstract A comprehensive mathematical model is developed for the dynamic calculation of the molecular distributed properties (i.e. MWD and CCD) in a gas-phase, catalytic, ethylene-1-butene copolymerization, FBR, taking into account the various kinetic, micro- and macroscopic phenomena in the reactor. The effects of the two single-site catalyst mass fractions and reactor operating conditions on the production of polyolefins with ,tailor-made' bimodal molecular properties are investigated. It is shown that PE grades with either a bimodal MWD or CCD can be produced in a single FBR, using a mixture of two single-site catalysts under properly selected operating conditions. [source] Effect of polymerization method on structure and properties of cationic polyacrylamideJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Yinghua Shen Abstract Acrylamide and 2-(methacryloyloxy)ethyltrimethylammonium chloride (AM/MADQUAT) copolymers were synthesized by solution and inverse microemulsion polymerization using (NH4)2S2O8/NaHSO3 as redox initiator at the same feed mole ratio, and their microstructure, such as sequence distribution and composition distribution, was calculated from monomer reactivity ratios of different polymerization methods. The results show that charge distribution is more uniform for copolymer prepared in inverse microemulsion than that in solution, and copolymer composition distribution is close to unity, and maintains approximately at the feed ratio. Furthermore, the influence of the two structures of cationic polyacrylamides on kaolinite floc size and effective floc density, reduction of Zeta potential and floc compressive yield stress had been investigated at pH 7. The results show that the kaolinite floc size and effective floc density are strongly dependent upon copolymer microstructure, with greater floc size and lower effective floc density being observed for copolymer prepared in inverse microemulsion than for that in solution. Copolymer microstructure has a marked effect on the Zeta potential, whose reduction in the magnitude was much greater in the presence of copolymer prepared in inverse microemulsion than that in solution. Greater compressive yield stress was achieved for the strong flocs produced by copolymer prepared in inverse microemulsion than for the weak flocs produced by that in solution. The difference in flocs compressive yield stress may be attributed to flocs structure. Therefore, in this article, a correlation between the cationic polyacrylamide structure and flocculation property for kaolinite suspension was established. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Model development for semicontinuous production of ethylene and norbornene copolymers having uniform compositionAICHE JOURNAL, Issue 3 2009Shaojie Liu Abstract Terminal and penultimate models for controlling copolymer composition distribution (CCD) in ethylene and norbornene (NB) copolymerization were developed by taking into account the variation of active site concentration with the initial comonomer ratio. The models were validated by batch polymerization experimental data. The terminal model gave better correlation with the composition data whereas the penultimate model had a better fit to the rate data. The terminal model was then used to design NB feeding policies in semicontinuous processes for targeted CCD profiles. Based on the model results, a series of ethylene-NB copolymers with various NB contents were prepared. With the same NB content, the semicontinuous process produced a uniform composition, whereas the batch process yielded broad CCD. The batch samples had lower Tg values and broader transition ranges, even yielded crystalline materials. In contrast, the semicontinuous samples overcame the disadvantages. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Copolymer Sequence Distributions in Controlled Radical PolymerizationMACROMOLECULAR REACTION ENGINEERING, Issue 2-3 2009Amin Zargar Abstract Although simulations of polymerizations have been performed using population-balance and method-of-moments techniques to determine the properties of copolymers, the method used most often to estimate copolymer composition distribution is based on probabilistic arguments and is not entirely compatible with the population balance approach. In this paper, a model based on the method of moments is presented that determines not only the molecular weight and copolymer composition characteristics, but also allows prediction of the copolymer distribution. The method is applied to controlled-radical polymerization. Batch polymerizations are simulated to illustrate the effect of composition drift, and shot polymerizations are simulated to show the potential to produce copolymers with customized sequence distributions. [source] | ||||||||||