Sorption and diffusion in semi-crystalline polymers


Responsible persons:

Sorption equilibria and diffusion dynamics of penetrants in semi-crystalline polymers significantly influence polymerization processes and subsequent product treatment such a degassing. In polymerizations, the equilibrium solubilities determine maximum reaction rates, while diffusion can be the rate limiting step if the polymerization reaction is fast. In the degassing step, the diffusion rate determines the necessary residence time. Sorption is also important with respect to polymer softening, because swollen polymers soften at lower temperatures.

We study the sorption and diffusion in polyethylene (PE) and polypropylene (PP), which are the most important polyolefins. For the experiments, we use the gravimetric and pressure-decay techniques. Measured equilibrium data are correlated with PC-SAFT calculations, while several models are used for diffusion, namely (i) Ficks law, (ii) multigrain or bi-disperse model, and (iii) model for transport in reconstructed 3D porous particles. We also study the co-sorption in polyolefins, i.e., the sorption of binary gas mixtures (e.g., ethylene and 1-hexene or ethylene and propane).


In the case of polyolefins, the sorption processes depend on morphology. The characterization of polyolefin morphology is thus essential for the analysis of transport in polyolefins, as it provides input data for mathematical models and as the comparison of experimentally measured sorption data with the morphology enables to study the relations between structure and transport. We thus utilize several experimental techniques for the characterization of polyolefin morphology. These methods are: (i) X-ray micro-tomography, (ii) AFM, (iii) time-domain NMR, (iv) confocal Raman microscopy and (v) DSC (provided externally).



Published results:

Chmelař J., Smolná K., Haškovcová K., Podivinská M., Maršálek J., Kosek J.: Equilibrium sorption of ethylene in polyethylene: Experimental study and PC-SAFT simulations, Polymer, 2015, 59: 270-277.

Hajová H., Pokorný R., Kosek J. Diffusion Transport in Reconstructed Semi-Crystalline Structure of Polyolefins. Polymer Reaction Engineering – 10th International Workshop, 2011, 302, 121–128. 

Bobák M., Gregor T., Bachman B., Kosek J. Estimation of morphology characteristics of porous poly(propylene) particles from degassing measurements. Macromolecular Reaction Engineering, 2008, 2 (2): 176 – 189.

Novák A., Bobák M., Kosek J., Banaszak B.J., Lo D., Widya T., Ray W.H., de Pablo J.J.: Ethylene and 1-hexene sorption in LLDPE under typical gas-phase reactor conditions: Experiments. Journal of Applied Polymer Science, 2006, 100 (2), 1124–1136.



Juraj Kosek
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+420 220 443 296

University of Chemistry and Technology Prague
Department of Chemical Engineering
Technicka 5
166 28 Prague 6
Czech Republic

University of West Bohemia
New Technologies Research Centre (NTC)
Univerzitní 8
306 14 Pilsen
Czech Republic