Measurement of Co2 Permeability in Polymer Films

A simple and sensitive method for measuring CO ₂ permeability in polymer films has been developed. The method is based on the use of ¹⁴ CO ₂ . At time zero ¹⁴ CO ₂ is injected on the high pressure side of the cell. Permeation is monitored with a Geiger counter which senses ¹⁴ CO ₂ on the low pressure side of the cell. The counts/time on the low pressure side are proportional to the total concentration of CO ₂ which has diffused through the film. With the known source concentration the volume-time curve is constructed and the permeability and time lag are calculated. The system sensitivity as it is presently configured is on the order of 10 ^-15 em ³ (STP).cm/cm ² .sec.cm Hg. Results are presented for a measurement of a 0.025 cm polycarbonate film.