ISO 9932:2021 pdf download – Paper and board — Determination of water vapour transmission rate of sheet materials — Dynamic sweep and static gas methods.
7 Preparation of test pieces Test pieces shall be representative of the sample and shall take into account, where appropriate, variations within and between sheets and batches. The test area shall be free from faults likely to affect the determination. The faces shall be designated one and two respectively. Where the two faces or the material can be distinguished, face one shall denote the face exposed to the wet side in service. Carefully, in order to avoid damage to the test area, cut 10 test pieces to the required size and drill holes as necessary for the test cell being used. Composite materials may have a core of permeable material which can provide a secondary path for moisture permeation if the edges are left exposed. In this case apply aluminium foil tape to the edges of such test pieces. The foil tape shall cover the edges and overlap the face by at least 10 mm. The foil tape shall be of the self-adhesive type, using dead soft tempered foil at least 40 µm thick. Thick test pieces of homogenous construction may also allow moisture permeation through the edges and should also be treated as above. NOTE No definitive statement can be given about the thickness at which sealing the edges becomes necessary, but as a general rule this should not be necessary for thicknesses less than 5 mm. 8 Procedure The precise method to be used shall be obtained from the manufacturer’s operation manual. The general procedure is as follows. 8.1 Method A Fill the lower part of the test cell with water or the appropriate saturated saline solution containing a solid phase in order to obtain the required humidity and clamp the test piece in the cell with face one towards the wet side of the cell. Set the apparatus to the required temperature. Operate the apparatus in accordance with the manufacturer’s instructions to obtain a reading, ensuring that a steady state has been reached.