Polyolefins in hydrocarbon solvents exhibit a lower critical solution temperature (LCST) in which the polymer solution splits into a liquid-liquid equilibrium (LLE). This phenomena may cause problems during a solution polymerization, as operating in an excessively high temperature, or low pressure, will result in the polymerization occurring in the two phase region. Alternatively, the phenomena may be useful in a post-polymerization process when separating the polymer from the solvent. For these reasons a detailed map of the LLE boundaries would be useful. The boundaries depend on three parameters: (1) the polymer molecular weight distribution, (2) the polymer chemical composition distribution, and (3) the solvent mixture. Here, we present ongoing work at Corporate Strategic Research to systematically map out the LLE phase boundaries as a function of these parameters. Experimental work involves measuring the LLE of systems which cover a wide range of polymer molecular weights, polymer chemical compositions, and solvent mixtures. This requires well characterized, narrow molecular weight and composition distribution polyolefins. Modeling is also required as the permutations of polyolefin types and solvent mixtures are too large to cover experimentally. Different variants of statistical associating fluid theory (SAFT) equation of state models have been evaluated to determine the optimum for interpolating the gaps in the experimental data.

Measuring and modeling the liquid-liquid equilibrium phase boundaries of polyolefins in hydrocarbon solvents

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.