Effects of casting and post casting annealing on xylene isomer transport properties of Torlon® 4000T films
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AbstractProcedures for Torlon® 4000T membrane formation were developed to provide attractive and repeatable xylene separation properties. Torlon® 4000T membrane films cast by our method were investigated in terms of thermally induced imidization, molecular weight enhancement, and solvent removal. After development of the Torlon® 4000T casting procedure, pervaporation of a xylene mixture (i.e. 30% para-xylene, 30% meta-xylene, 30% ortho-xylene, and 10% ethylbenzene) was performed in both Torlon® 4000T and post casting annealed Torlon® 4000T films. The xylene pervaporation in annealed Torlon® 4000T film at 200°C gave a permeability of 0.25 Barrer and a selectivity of 3.1 (para/ortho) and 2.1 (para/meta) respectively. A so-called " permeability collapse" reflecting an accelerated reduction in the free volume is consistent with significant temperature-induced changes in the films observed after thermal annealing at 300°C. This conditioning effect is induced by a combination of heat treatment and the presence of the interacting aromatic penetrants. Optical methods were used to verify that the density of annealed samples exposed to xylene for 5 days eventually increased, suggesting that the membrane is originally swollen upon initial xylene exposure, and then relaxes to a more densified, and more discriminating state. © 2010 Elsevier Ltd.
CitationChafin R, Lee JS, Koros WJ (2010) Effects of casting and post casting annealing on xylene isomer transport properties of Torlon® 4000T films. Polymer 51: 3462–3471. Available: http://dx.doi.org/10.1016/j.polymer.2010.05.028.
SponsorsThe authors would like to acknowledge financial support from BP, The Coca Cola Company, and Award No. KUS-I1-011-21 made by King Abdullah University of Science and Technology (KAUST). Also, we would like to convey special thanks to Chuck Hoppin for his assistance in making the viscometry measurements.