Gas permeability in the polystyrene films uniaxially drawn under CO2 plasticizing

 Gas permeability coefficients, Ps, of CO₂, O₂, and N₂ have been measured in four kinds of polystyrene (PS) films: an unconditioned film with no orientation (1), a high pressure CO₂-conditioned film with no orientation (2), an uniaxially hot-drawn film with some orientation (3), and a film uniaxially drawn under CO₂ plasticizing with some orientation (4). Wide angle X-ray diffraction (WAXD) scans for each sample have also been made. High-pressure CO₂-conditioning effect was confirmed from the result that P values for any permeation gas in sample 2 were larger than those in sample 1. Values of P for any gas in sample 3 were almost close to those in sample 1 and decreased slightly with Hermans orientation function, f. Gas permeability coefficients in sample 4 are larger than those in sample 3 over the whole range of f studied in this work and increased with f. These results were discussed from a viewpoint of inter-segmental distances for PS films. Received: 2 January 1997 / Accepted: 27 March 1997