Experimental and theoretical investigation of solubility and diffusion of ethylene in semicrystalline PE at elevated pressures and temperatures

Abstract

ABSTRACT:The solubility and diffusivity of ethylene in semicrystalline polyethylene were experimentally measured using a magnetic suspension microbalance. The sorption measurements were carried out at temperatures up to 80°C and pressures up to 66 atm. The experimentally measured solubilities were found to decrease with increasing temperature and increased with ethylene pressure in good agreement with the predictions of the Sanchez-Lacombe latticefluid model. The diffusivity of ethylene in semicrystalline polyethylene films was estimated from the reduced sorption curves using the half-time method. The experimentally determined diffusivities were compared with theoretical values predicted by a new molecular hybrid model, which combines the characteristic features of the Pace-Datyner diffusion model with those of the Kulkarni-Stern free-volume model. The ethylene diffusion coefficient was found to increase with temperature and/or the ethylene-sorbed concentration.

Diffusion of Model Contaminants in High‐Density Polyethylene

“…[25][26][27][28][29][30] Lately, Doong and Ho [31] developed a hybrid model for the calculation of the diffusion coefficient of aromatic hydrocarbons in semicrystalline PE, which combined the main features of the Pace-Datyner molecular model [16,[18][19] with Vrentas-Duda's free volume approach. [23][24] Inspired by this approach, Kiparissides et al [32] calculated D for organic vapors in semicrystalline PE by formulating a new hybrid model also based on the Pace-Datyner molecular theory, but now combined with Kulkarni and Stern's free volume model. [33][34] Both these models proved reasonably successful for the case of the vapors tested, yet, their adequacy in the case of liquid penetrants remains untested.…”

Partial Molar Volumes and Thermal Expansion Coefficients as an Explanation for Co-Solvent Effect of Penetrants in Multicomponent Polymer Mixtures

“…However, in addition to what was discussed in the previous publication [ 3 ] (where the original methodology was applied to a number of binary (penetrant/semicrystalline polymer) systems), it has been shown by various authors [ 4,7,[26][27][28][29][30] that properly fi tted binary interaction parameters enable the SL EoS to estimate various thermodynamic properties of mixtures involving semicrystalline polymers with an acceptable error (i.e., usually the error between experimental values and fi tted SL EoS values is less than 10%). Therefore, in this work the binary interaction parameters of the SL EoS were tuned to account for the effect of polymer crystallinity on gas(es) sorption in the polymer, at different temperatures and pressures.…”

Comparison of catalytic ethylene polymerization in slurry and gas phase

“…One possible explanation is the high crystallinity observed at higher temperatures. Monomer diffusion through crystals is negligible [72]. Because of this "crystal barrier", the monomer concentration near the active sites decreases and the mass transfer limitation on the propagation reaction becomes obvious.…”