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Predicting Solubility and Diffusivity of Gases in Polymers under High Pressure: N-2 in Polycarbonate and Poly(ether-ether-ketone)
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
Materials Technology Research Institute.
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2013 (English)In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 52, no 26, 8655-8663 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to develop a model that predicts the gas solubility and the sorption and desorption kinetics in polymer granulates over large temperature and pressure intervals. Besides the part predicting the solubility and diffusivity, the model involves the simultaneous solution of the diffusion equation and the heat equation in three dimensions using a finite element method (FEM). When the temperature- and pressure-dependent solubility of a specific polymer/gas combination is not known, an improved version of the non-equilibrium lattice fluid model (NELF) is used to predict the solubility. The improvement of the NELF model includes the use of Hansen's solubility parameters, and it uses pressure-volume-temperature (PVT) data from two new empirical models, which accurately estimate polymer densities over a wide range of temperatures and pressures. The new solubility model predicted the solubility-pressure data of N-2 in poly(ethyl methacrylate) and N-2 and CH4 in polycarbonate (PC) at pressures below 4.5 MPa, without using any adjustable interaction parameters. The model was used to predict the solubility of N-2 in poly(ether-ether-ketone) (PEEK) and PC at a very high pressure (67 MPa). Experimental N-2 solubility data were obtained with a specially built reactor yielding high pressure and temperature. For PEEK, it was possible to predict the very high pressure solubility using a gas-polymer interaction parameter obtained from data taken at low pressures In addition, a new free-volume-based diffusivity model requiring no adjustable interaction parameters was developed, and it successfully predicted the desorption kinetics of N-2 from PEEK and PC.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2013. Vol. 52, no 26, 8655-8663 p.
Keyword [en]
Desorption, Diffusion, Ethers, Forecasting, Ketones, Partial differential equations, Polycarbonates, Polymers
National Category
Polymer Chemistry
URN: urn:nbn:se:kth:diva-93549DOI: 10.1021/ie300975hISI: 000321541600005ScopusID: 2-s2.0-84879862466OAI: diva2:516943
EU, European Research Council, 218346Swedish Research Council, VR-05-6138

Previous title: Predicting Solubility and Diffusivity of Gases in Polymers under High Pressure: N2 in Polycarbonate and Poly(ether-ether-ketone)

QC 20130205

Available from: 2013-02-05 Created: 2012-04-20 Last updated: 2013-08-12Bibliographically approved
In thesis
1. Simulations of Semi-Crystalline Polymers and Polymer Composites in order to predict Electrical, Thermal, Mechanical and Diffusion Properties
Open this publication in new window or tab >>Simulations of Semi-Crystalline Polymers and Polymer Composites in order to predict Electrical, Thermal, Mechanical and Diffusion Properties
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Several novel computer simulation models were developed for predicting electrical, mechanical, thermal and diffusion properties of materials with complex microstructures, such as composites, semi-crystalline polymers and foams.

A Monte Carlo model for simulating solvent diffusion through spherulitic semicrystalline polyethylene was developed. The spherulite model, based on findings by electron microscopy, could mimic polyethylenes with crystallinities up to 64 wt%. Due to the dendritic structure of the spherulites, the diffusion was surprisingly independent of the aspect ratio of the individual crystals. A correlation was found between the geometrical impedance factor (τ) and the average free path length of the penetrant molecules in the amorphous phase. A new relationship was found between volume crystallinity and τ. The equation was confirmed with experimental diffusivity data for Ar, CH4, N2 and n-hexane in polyethylene.

For electrostatics, a novel analytical mixing model was formulated to predict the effective dielectric permittivity of 2- and 3-component composites. Results obtained with the model showed a clearly better agreement with corresponding finite element data than previous models. The analytical 3-component equation was in accordance with experimental data for nanocomposites based on mica/polyimide and epoxy/ hollow glass sphere composites. Two finite element models for composite electrostatics were developed.

It is generally recognized that the fracture toughness and the slow crack growth of semicrystalline polymers depend on the concentrations of tie chains and trapped entanglements bridging adjacent crystal layers in the polymer. A Monte Carlo simulation method for calculating these properties was developed. The simulations revealed that the concentration of trapped entanglements is substantial and probably has a major impact on the stress transfer between crystals. The simulations were in accordance with experimental rubber modulus data.

A finite element model (FEM) including diffusion and heat transfer was developed for determining the concentration of gases/solutes in polymers. As part of the FEM model, two accurate pressure-volume-temperature (PVT) relations were developed. To predict solubility, the current "state of the art" model NELF was improved by including the PVT models and by including chemical interactions using the Hansen solubility parameters. To predict diffusivity, a novel free-volume diffusion model was derived based on group contribution methods. All the models were used without adjustable parameters and gave results in agreement with experimental data, including recent data obtained for polycarbonate and poly(ether-etherketone) pressurized with nitrogen at 67 MPa.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 59 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2012:15
National Category
Polymer Chemistry
urn:nbn:se:kth:diva-93519 (URN)978-91-7501-290-2 (ISBN)
Public defence
2012-04-20, F2,, Lindstedtsvägen 28, entréplan, KTH, Stockholm, 10:00 (English)
QC 20120420Available from: 2012-04-20 Created: 2012-04-20 Last updated: 2012-04-23Bibliographically approved

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