Various methods of test for gas transmission rate of polymer membranes were summerized, which cover the determination of the steady state rate of transmission of a gas through polymers in the form of film, sheeting, laminates and polymer coated papers. They provide for the determination of (a) gas transmission rate (GTR), and (b) permeability coefficient in the case of homogeneous materials, and (c) diffusion coefficient.
Methods are divided into two main groups; A) non-equable pressure method and B) equable pressure method. In the non-equable pressure method, the pressure difference exists across the sample and the permeated gas through the sample is measured by a monometric method or volumetric method. In the manometric method, when the lower pressure side of the sample is initially evacuated at 10 -5 -10 -6 mmHg, the transmission of the gas through the test specimen is indicated by a change in pressure which is measured by Mc Leod gauge or an MKS Baratron pressure transducer. This method is called “high-vacuum technique ”. When the lower pressure side of the sample is initially evacuated at 10 -1-10 -2 mmHg, the transmission of the gas is measured by a cell manometer, namely a closed end U-tube manometer. This method is called “low-vacuum technique ”. In the volumetric method, the low pressure side of the sample is maintained near atmospheric pressure and the transmission of the gas is indicated by a change in volume. In the equable pressure method, the total pressures of the both sides of the sample are equal. The permeated gas is measured by a detector system, for example, cas chromatography, thermal conductivity. When oxygen is a test gas, the oxygen electrode is available.
In both methods (A) and (B), the principles, apparatus and calculations were described here in detail.
