Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Software for the prediction of solubility, swelling and concentration

A Software using Delphi TM 6 was developed for processing raw data of solubility and for predicting the swelling of the polymer and the concentration of a penetrant in a polyolefin.

The equilibrium sorption of gaseous propylene in PP particles of different diameters was measured using an electromagnetic thermal balance. The swelling of polypropylene caused by the sorption of propylene was estimated assuming ideal mixing. The measured solubilities were correlated with the S-L EOS. The predicted polymer swelling from S-L EOS coupled with the optimised binary interaction parameters was compared to the estimated swelling based on ideal mixing. The concentration of sorbed propylene in the amorphous part of polypropylene was estimated. Unexpectedly, Henry's law with a temperature-dependent constant could describe propylene concentration. The measured sorption data were used for the comparison of gas and liquid phase kinetics of propylene polymerization with a highly active 4th generation Ziegler-Natta catalyst. Precise 'isoperibolic' polymerization rate profiles were measured in liquid pool polymerisation, while gas phase polymerisation profiles were measured using the method of 'reactive bed preparation' under isoperibolic conditions. It was found that the same catalyst system at the same temperature and hydrogen concentration has the same relative activity in liquid pool and gas phase polymerization.

Furthermore, a review of the sorption of ethylene and α-olefins in PE is done. The influence of crystallinity, type of polyethylene, and type of catalyst used, branching, and polyethylene structure on penetrant sorption is discussed. The S-L EOS has been used for quantitative comparison of the studied systems. The predicted polymer swelling from S-L EOS using the optimised binary interaction parameters is compared to the measured swelling isotherms for the polyethylene samples studied. An excellent match between the swelling isotherms obtained from the dilation isotherms and the values predicted by S-L EOS are obtained for all the systems reviewed. It is found that no general correlation can be used for a precise description of the concentration or solubility of ethylene/α-olefins. It is concluded that several structural factors, such as crystallinity, branching, type of comonomer, comonomer composition, molecular weight, molecular weight distribution and comonomer composition distribution, contribute significantly to the sorption process.

Reported by

Industrial Polymerization Processes- Faculty of Science and Technology / University of Twente (IPP/UT)
Industrial Polymerization Processes (IPP), Faculty of Science and Technology (TNW), University of Twente, P.O. Box 217
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