466467 Thermodynamics of Sorption and Swelling in Polyethylene at Gas-Phase Polymerization Conditions
In our work, sorption and diffusion of low molecular weight penetrants is measured gravimetrically, where we measure the mass increase of polymer due to the gas sorption. The gravimetric data have to be corrected to the buoyancy force of the pendulous swollen polymer. Experimental measurement of swelling was carried out in video-microscopic apparatus. The method is based on the visual observation of a polymer particle by microscope with attached digital camera. The measured swelling isotherms were used in the evaluation of the gravimetric data.
This contribution presents results for sorption and swelling of ethylene, co-monomers (1-hexene, 1-butene) and inert diluents (propane) in various PE grades at conditions relevant to catalytic polymerization of olefins. This work stands out of similar studies in the open literature due to: (i) systematic measurement for a broad range of PE densities from 0.90 to 0.96 g/cm3 covering practically all relevant grades, (ii) reporting a comprehensive set of swelling data for several penetrants, (iii) systematic measurements for several penetrants at a range of industrially relevant temperatures and pressures, and (iv) modelling the sorption data by the advanced PC-SAFT equation of state.
The experimental data and observed trends presented in this work contribute to the complex understanding of the mass transport and sorption equilibria of penetrants in polymers.