BSIS015106-4:2008 10:22, ISO 15106-4:2008(E) t as of 23/03/2009 2 5 13 3 4 correct 7 16 12 8 Version 14 9 Council, 11 10 Training Key 1 specimen S 2 transmission cell B 3 wet chamber Vocational 4 dry chamber with hydrophobic filter-paper 5 gas supply 6 gas controller 7 humidity controller with distilled or deionized water (water reservoir) 8 sampling loop 9 gas chromatograph Council, 10 data processor 11 vacuumpump 12 carrier gas forgas chromatograph 13 gas exhaust 14 carrier gas exhaust Trading 15 switching valve 1 16 switching valve 2 Figure1Exampleof apparatusformeasuringWVTRbygas chromatography Vocational copy: Licensed ISO2008-All rights reserved 3 BS ISO 15106-4:2008 10:22, ISO 15106-4:2008(E) /2009 Test conditions The test conditions should preferably be chosen from those given in Table 1. tas of23/03/ Table1Choiceof test conditions Set of test conditions Temperature RH of wet chamber RH of dry chamber °c % % 1 25 ± 0,5 90 ± 2 0 2 38 ± 0,5 90 ± 2 0 Version correct 40 ± 0,5 90 ± 2 0 23 ± 0,5 4 85 ± 2 5 25 ± 0,5 75 ± 2 0 Test conditions other than these, for example test conditions specified in Iso 291, shall be agreed upon by the interested parties. 9 Calibration graph Council Prepare dilute solutions of water in alcohol at different levels of water concentration. Inject a known volume of each solution into the gas chromatograph using a liquid syringe and record the chromatogram for each under the same conditions. Determine the area of the peak in the chromatogram ining corresponding to the injected water. Produce a calibration graph by plotting water concentration against peak area and drawing a straight line S through the points. In the case of 1 % (by mass) of water in methanol, a straight line can be drawn from the origin through the point NOTE Vocational representing ameasurementonthis solution only. 10 Procedure 10.1 Spread a hydrophobic filter-paper (4 in Figure 1) having the same size as the gas transmission area over thebottomofthedrychamber. Council The hydrophobic filter-paper is used to support the specimen film and to ensure smooth water vapour of the filter bethe same as thedepthof the dry chamber. ling 10.2 Apply a thin, uniform coating of vacuum grease on the flat edges of the two halves of the transmission radi cell, and mount a specimen over the dry chamber in such a way that no creasing or slackness occurs. 1o.3 Place a rubber sealing-ring on the specimen, then set up the upper part of the cell. Clamp the two chambers together with a uniformpressure so thatthe specimen is compietely sealed inplace. 10.4 Start the vacuum pump and evacuate all the air from the dry chamber. Care is necessary here, because Vocat the time taken to exhaust the cell completely will depend on the permeability of the specimen under test. 10.5 Introduce water vapour into the wet chamber through the humidity controller in such a way that the wet copy: through the specimen is evacuated by the vacuum pump. 1) PolyflonTM is an example of a suitable product available commercially. This information is given for the convenience of Licensed users of this part of so 15106 and does not constitute an endorsement by IsO of this product. 4 @ISO 2008-Allrights reserved BS ISO 15106-4:2008 3/2009 10:22, ISO15106-4:2008(E) 10.6 By closing valve 2 (16 in Figure 1), start collecting the water vapour which permeates through the specimen in the sampling loop (8). After a predetermined period of time t, close valve 1 and sweep the water f23/03/ Using the integrator of the chromatograph, determine the area of the peak in the chromatogram corresponding to the watervapour. Determine, from the calibration graph prepared in Clause 9, the amount of water vapour my which has accumulated in the sampling loop. tas of It is recommended that the purity of the carrier gas be greater than 99,99 %. 10.7 Repeat steps 10.4, 10.5 and 10.6 until consecutive measurements show that a steady state has been , Version correct t is constantto within±5% 10.8 Either before