Description:
Testing method aplicable to nearly all materials, e.g. plastic and polymer films, preferably with low water vapour permeability. For samples with high water vapour permeability, the gravimetric method according to DIN 5312-A or ASTM E-96 is more suitable.
Result Unit:
WVTR (water vapour transmission rate) in g/m2*d;
Related to the thickness: P(permeating coefficient)in g*mm/m2*d.
(Related) Standards:
DIN 53122-1 / DIN 53122-A,
ISO 2528:1995,
ASTM E-96.
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 until test pressure is reached. After reaching the desired temperature, the 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. A tempered test chamber is flushed by a carrier gas with a defined humidity. The water that has permeated through the sample is carried to the detector by a second carrier gas. The concentration is determined and the permeation rate is calculated.
Detection limit:
0.001 g/m2*d. The norm proposes a range of 0.01 – 5 g/m2*d for a sample size of 100 cm2. The detection limit also depends on the nature and thickness of the specimen. The method is recommended for permeation values > 0.1 cm3/m2*day, because at lower rates the measurement times become very long and cost for the measurement rises.
Required specimen:
For testing please send us a sheet of the approximate size of a sheet of paper (DIN A4, 210*297 mm). For non flat specimens: please send after consulting with us. The standard does not define the sample size or thickness, a measuring area of at least 100 cm2 is proposed. 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 53370. We recommend the measurement of three independent samples per test (minimum number not regulated by 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 yourself, 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:
Water or water vapour.
Test conditions:
The standard proposes the following climates:
A – 23 °C 90 %r.h.;
B – 38 °C 90 %r.h.;
C – 25 °C 75 %r.h.;
D – 23 °C 85 %r.h.;
E – 20 °C 85 %r.h.;
We will test with other climate conditions on your request. Please contact us for information on 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.
You find this article here as a PDF. We also do the test sample manufacture for you.
