Measurement of gas permeability of polymers. I. Permeabilities in constant volume/variable pressure apparatus



A constant volume/variable pressure gas permeability apparatus is described that provides accurate determination of permeabilities ranging from less than 10−1 to 106 centibarrers. Metal construction, variable temperature control, adjustable downstream pressure and constant volume, and a differential pressure transducer with automatic recording are design features that permit detailed permeability studies under a variety of environmental conditions. Pressure effects on polymer films have been investigated up to 1000 psi, and the relation of gas concentration to permeability has been studied by varying the downstream pressure and volume conditions. The high feed pressures have significantly shortened the time required to obtain meaningful data on low-permeability materials after steady-state conditions are achieved, and the variable-temperature control has permitted evaluation of temperature-related phenomena.