1990 Volume 46 Issue 12 Pages 568-574
The origin of the error in the measurement of small diffusional time-lags (θ) was studied by use of an aluminum foil with an orifice in place of a polymer membrane. The error was caused by the flow of the low-concentration gas, i.e., the pressure gradient in the downstream side. Based on the result, a new apparatus for the measurement of small θ was developed, in which a high-response transducer was directly attached to the membrane to monitor the pressure of the downstream side. A microcomputer was used for the on-line measurement of the pressure and the data analysis. The performance of this new system was tested for low density polyethylene and silicone rubber samples with various thicknesses. By this system, θ as small as ca. 0.2s could be measured. The errors in the measurement of small θ due to the structure of the downstream side of the permeation cell and the setting up of the start time in the time-lag measurement are also discussed.
