ISO 9932:2021 pdf download – Paper and board – Determinationof water vapour transmission rate of sheet materials — Dynamic sweep and static gas methods
ISO 9932:2021 pdf download – Paper and board – Determinationof 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 laces 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 irn 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
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. Record this reading and repeat the procedure for the remaining test pieces so that five readings are obtained with face one towards the wet side and five readings with face two towards the wet side.
8.2 Method B
Clamp the test piece In the cell with face one towards the wet side. Place the cell in the humidity cabinet at the required temperature and relative humidity. Record the rate of electrolysis of the water vapour passing into the cell as indicated by the microammeter until a steady state has been reached. Record the reading and repeat the procedure so that five readings are obtained with face one towards the wet side and five readings with face two towards the wet side.
8.3 Barrier material having one face of uncoated paper
Where one lace of a barrier material consists of uncoated paper, and this lace is towards the dry side, difficulties can be expected. All water must be removed from the paper by the dry gas before a constant water vapour transmission rate is indicated on the meter or recorder.
The pre-conditionlng can last several days and care should be taken to ensure that a true steady state has been reached. It is recommended that the test be carried out only with the paper towards the wet side.
Where a water vapour transmission rate determination yields a value grossly different from comparable samples of the same material, the execution of the particular determination is suspect and shall be investigated and, If necessary, repeated.8.4Creased material
For some purposes it may be necessary to determine the transmission rate of creased material; insuch cases carry out the creasing procedure described in IS0 2528:2017,Annex A and then follow theprocedure of method A or method B as appropriate.
9Expression of results
Calculate the mean and standard deviation of the separate determinations carried out with face oneand face two facing the wet side respectively.
Express the results in grams per square metre per 24 h [g/([m2-d)] for each side, tested to two significantfigures.
10.1 General statement of the precision
There is scepticism that a proper seal can be done for paperboard and some nonwovens. There is also alack of good repeatability data for these two types.