Description:
Universal testing method applicable to nearly all gases for the determination of gas transmission rate through rubber and elastomer depending on temperature and testing gas.
Result Unit:
According standard:
Permeation coefficient Q(T) m2*Pa-1*s-1 (indicates how much m3 gas (STP: 0 °C, 101325 Pa) permeate in 1 s through a sample of 1 m thickness and 1 m2 surface at a partial pressure difference of 1 Pa at a constant temperature T) or normalised to the thickness of the specimen: gas permeability D m*s-1*Pa-1
(Related) Standards:
ISO 1399:1983: Testing of rubber, Determination of gas permeability, test with constant volume,
ISO 2872:1977: Testing of rubber, Determination of gas permeability, test with constant pressure.
Test method:
The test sample is mounted in a permeation cell so as to form the barrier between two chambers. One chamber is filled with the test gas till test pressure is reached. After reaching the desired temperature, measurement is started. The permeation gas displaces liquid out of a U-tube which is connected with the other chamber. The permeation coefficient is calculated as the slope of the displaced volume against time.
Detection limit:
Typical range ot the measurement values according to the standard: 1*10-18 bis 150 * 10-18 m2 s-1 Pa (for a 1 mm thick sample: cm3*mm*bar/m3*Tag: 8.64-1296).
Elastomers are quite good permeable for gases. So detection limits of Mecadis equipment will not be reached (< 0.1 cm2*mm*bar/m3*day). Please inform us, if you sent us samples of polymer blend, coated or multilayer materials.
Required specimen:
For testing please send us a sheet of about the size of a sheet of paper (DIN A4, 210*297 mm). For non flat specimans: please send after consulting with us.
Scope of the standard:
At least 8 cm2 active area of the samples.
Thickness 0,1-3 mm.
The specimens shall be uniform in thickness, representative for the material and free of pinholes and folds. On request we measure your sample thickness according to DIN 53534. We recommend the measurement of three independent samples per test (minimum number not regulated in the standard). Our standard is to measure samples of 20 µm – 3 mm, others on request.
Required sample dimension: we perform the preparation of the samples for you. For different test gases and type of samples we use different sized samples. If you want to conduct the cutting of the specimens please contact us for the required dimensions. For sensistive coating test sometimes it makes sense to prepare first the support followed by the coating. Please inform us, if your samples tend to mechanical failure under applied pressure (of the test gas or the sealings).
Testing medium:
Gases, vapours, solvent above boiling point with standard: O2, CH4, N2, Ar, He, H2, Cl2. Our permeation measurement cells are all-purpose because they are resistant to corrosion. Please contact us for special applications. The testing method is normally limited to substances or mixtures which contain substances with very skewing permeation rates.
Test conditions:
Scope of the standard: 30 °C +/- 1°C
Gas pressure: not regulated by the standard, typical till 5 bar (500 kPa)
Temperature: typical according standard 20 °C – 125 °C
Mecadi’s possible testing temperatures: standard -50 °C up to +150 °C, other temperatures on request.
Temperature tolerance possible with Mecadi equipment: better than +/- 0.1 K (target: +/- 0.01 K) Experience shows that +/- 1 K tolerance leads to permeation rate scattering up to 20 %.
Mecadi’s possible testing pressures: standard: up to 100 bar, others on request.
Please contact us for information about special effects and requirements for the samples at high pressures. Also possible are temperature profiles (nonisothermic measurements) for the determination of morphology changes and the influence of media and pressure on polymer properties. Based on this method, Mecadi offers further examination to determine gas solubilities (sorption and desorption), diffusion coefficients and the measurement of break through times through barriers. Furthermore, interactions between media and polymer can be investigated. Thus the predictions according resitance, physical and chemical reactions under process conditions can help in the selection process of materials.
For safety reasons, Mecadi does not conduct the detection of the the permeate with a mecury filled u-tube (scope of the standard) but an electronic pressure transducer (constant volume). Please contact us if you need standard conform detection.
You find this article here as a PDF. We also do the test sample manufacture for you.
