Thermodynamics of concentrated polymer solutions containing polyethylene, polyisobutylene, and copolymers of ethylene with vinyl acetate and propylene

Newman, Reagan; Prausnitz, John M.

doi:10.1002/aic.690190405

Cited by 39 publications

(16 citation statements)

References 18 publications

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“…A study by lwai et al (1985) indicates that Henry's constant, HI, is very similar for a given solute in both polyethylene and polypropylene, while Newman and Prausnitz (1973) found that the Flory interaction parameter is almost the same for polyethylene and ethylene-propylene copolymers. From these results it appears that HI for ethylene-propylene copolymers is not strongly dependent on polymer composition over the 0 to 100% ethylene range.…”

Section: Estimation Of Model Parametersmentioning

confidence: 99%

Effect of diffusion on heterogeneous ethylene propylene copolymerization

1994

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In heterogenous olefin polymerization with Ziegler catalysts, the influence of monomer mass transport in the growing granule on polymer properties has been extensively modeled, but it has not been possible to clearly establish the importance of diffusion experimentally since the multisited nature of most Ziegler catalysts can produce similar effects. In this study, ethylene-propylene copolymers were made with single-sited metallocene catalysts by slurry polymerization in liquid monomers. These copolymers had a relatively narrow molecular weight distribution with a composition distribution (CD) broader than expected for a single-site catalyst. Data analysis indicates that mass-transfer limitations in the polymer particles are the most likely explanation for the observed results. For amorphous copolymers, a diffusion IntroductionThe vast majority of the billions of pounds of polyolefins produced each year by Ziegler-Natta catalysts are made in multiphase reactors where the polymer exists as granules suspended in a fluid containing the monomers. For the most part, Ziegler polyolefins have a broad molecular weight distribution (MWD) with a ratio of weight to number average molecular weight (Q) of greater than 2 (4 to 10 is typical). Early investigations recognized that likely explanations of broad MWD included multiple active catalyst sites in the catalyst and nonsteady-state effects at the active site due to mass transport limitations (Zucchini and Cecchin, 1983). Initial attempts (Bul and Higgins, 1970) to model the diffusionheaction process at an active site embedded in a matrix of polymer indicated that diffusion alone could account for the observed MWDs. However, a large body of evidence now exists (see Zucchini and Checcin, 1983;Cozewith, 1987;Yechevskaya et al., 1987;and Haejaski et al., 1988) showing that multisited Ziegler catalysts are the rule rather than the exception. Thus, diffusion may indeed have an influence on polymerization rates and polymer properties, but if so, it would be very difficult to distinguish from the complicated polymerization behavior resulting from the multiple active sites. Consequently, there is no unequivocal data published in the literature that demonstrates whether polymer phase mass transport effects are important in Ziegler polymerizations.Recently, a new class of olefin polymerization coordination catalysts was discovered (Sinn et al., 1980) based on metallocene compounds of zirconium, titanium, or hafnium combined with an activator such as methyl alumoxane. These catalyst systems are capable of making the same range of olefin homo-and copolymers as Ziegler-Natta catalysts, however, they tend to be single-sited and to produce polymers with a most probable ( M J M , = 2) molecular weight distribution. In multiphase polymerizations with single-sited metallocene catalysts, deviations from the polymerization rate behavior or polymer properties expected for kinetically controlled reactions might well be strong evidence for diffusional effects on the polymerization.We have studie...

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Section: Estimation Of Model Parametersmentioning

confidence: 99%

Effect of diffusion on heterogeneous ethylene propylene copolymerization

1994

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“…Analysis of the Thermodynamic Data. Figures 2 and 3 show the change of the parameter with temperature for n-hexane and cyclohexane in EP copolymers with varying ethylene contents, which were obtained by this study, and compare them with the values obtained by Frensdorff (1964a) and Newman and Prausnitz, (1973).…”

Section: Resultsmentioning

confidence: 66%

Diffusion and Sorption in Ethylene-Propylene Copolymers: Comparison of Experimental Methods

Faridi¹,

Hadj-Romdhane²,

Danner³

1994

Ind. Eng. Chem. Res.

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The solubility and diffusion coefficients of various solvents in ethylene-propylene copolymers with different ethylene contents were measured over a temperature range of 30-200 °C using capillary column inverse gas chromatography and gravimetric sorption. The value of the Flory-Huggins parameter decreased with an increase in temperature. The infinitely dilute diffusion coefficients obtained by the two methods were consistent with each other. The data indicate that the diffusion coefficients and solubility parameters are independent of the ethylene content of the copolymers. The results obtained from the sorption technique were extrapolated using a free-volume theory to the limit of zero solvent concentration, and the free-volume model was used to interpret the diffusion data. Analysis of the diffusion data indicated that the inclusion of an activation energy in the free-volume model does not significantly improve the correlation of the diffusion data.

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“…Measurements were made on low‐density polyethylene (LDPE) to check the reliability of the adopted approach. This is simply because data for LDPE over the temperature range of interest (170 to 230 °C) are available in the open literature 3–10…”

Section: Introductionmentioning

confidence: 99%

Differences between Ziegler–Natta and Single‐Site Linear Low‐Density Polyethylenes as Characterized by Inverse Gas Chromatography

Zhao

Choi

2004

Macromol. Rapid Commun.

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Summary: Zero‐pressure weight‐fraction‐based Henry's constants $(H_{{\rm 12}}^0 )$ of two alkanes, two alkenes, and benzene in Ziegler–Natta (ZN) and single‐site (ss) linear low‐density polyethylenes (LLDPE) with different average branch contents, molecular‐weight averages ($\overline M _{\rm n}$ and $\overline M _{\rm w}$), and polydispersity indices (PDI) were measured in the temperature range of 170 to 230 °C using the technique of inverse gas chromatography. For both types of LLDPEs, the measured $H_{{\rm 12}}^0$ was insensitive to molecular weight and PDI. However, the branch content dependence differed significantly. In particular, ZN‐LLDPE exhibited a strong branch content dependence on $H_{{\rm 12}}^0$ while ss‐LLDPE did not. In fact, depending on the temperature and solvent used, $H_{{\rm 12}}^0$ of ZN‐LLDPE could drop as much as 21% with an increase in an average branch content from 13 to 35 branches per 1 000 backbone carbons, while the differences of $H_{{\rm 12}}^0$ between ss‐LLDPEs with comparable differences in branch content were well within experimental uncertainties (5%). This observation is also supported by the fact that comparable ZN‐ and ss‐LLDPEs exhibited larger differences in $H_{{\rm 12}}^0$ at higher average branch contents. The above findings strongly suggested that the liquid morphologies of ZN‐ and ss‐LLDPEs differ considerably. In particular, the local chain conformation and free volume characteristics (i.e., the size distribution and/or spatial distribution of the free volume holes) of them are rather different. Such differences become more pronounced at higher temperatures.

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Thermodynamics of concentrated polymer solutions containing polyethylene, polyisobutylene, and copolymers of ethylene with vinyl acetate and propylene

Cited by 39 publications

References 18 publications

Effect of diffusion on heterogeneous ethylene propylene copolymerization

Effect of diffusion on heterogeneous ethylene propylene copolymerization

Diffusion and Sorption in Ethylene-Propylene Copolymers: Comparison of Experimental Methods

Differences between Ziegler–Natta and Single‐Site Linear Low‐Density Polyethylenes as Characterized by Inverse Gas Chromatography

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