Standard: PAPTAC - D.15P
WATER VAPOUR TRANSMISSION RATE OF PAPER AND PAPERBOARD
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This method is for the gravimetric determination of w- a ter vapour transmission rate of paper and paperboard when one face of the sheet is exposed to essentially moisture free air and the other face is exposed to either (a) PAPTAC stan - dard atmosphere or (b) tropical atmosphere. The water vapour transmission rate is defined as the mass of water transmitted from one face of a sheet to the other per unit area per unit time. This method can be used for both creased and uncreased specimens. See Appendix 1 for the creasing procedure.
The behaviour of paper and paperboard under severe conditions can not be predicted from results obtained under normal conditions, therefore sheet materials intended for use in warm, damp environments must be tested using the tr-opi cal atmosphere.
the template should be about the same size but never larger than the eective opening of the cell. A hole through the template to admit air will facilitate removal after the wax has solidied. The diameter of the bottom face must be ac-cu rately known (to at least 3 signicant gures) so that the test area may be precisely determined.
3. Cutting Template . A circular disc to cut specimens so that they should lie at on the supporting grooves of the test cell.
4. Balance . An analytical balance of at least 160 g capac - ity, sensitive to at least 1 mg.
5. Test Chamber . A testing room or conditioning cabinet capable of maintaining continuously the appropriate hygrometric condition, and preferably so designed that the test cells can be weighed without removing them from the test chamber. The test chamber shall be provided with s-uit able means of supporting the test cells so as to aord free- ac cess to the conditioned air.
Ordinarily, when the test cells are exposed in the standard atmosphere, the test chamber will be a conditioned room in which the balance and the operator are enclosed. When, however, the cells are exposed in the tropical atmosphere, the balance and the operator will not be in the test chamber, because the conditions would be injurious to the balance and uncomfortable for the operator. In the latter case, a conditioning cabinet is used, preferably with a balance mounted on top and connected through a suitable weighing rod to the interior. If this type of weighing equipment is not available, and the cells must be removed for weighing, the specimens must be covered with suitable weighing covers while out of the cabinet. These covers, which are disc-like or dome-shaped, should be made of sheet aluminum sti enough to hold their shape and t closely at the base of the wax seal. Each cover should be provided with a knob or handle with which it may be lifted. The edge of the cover should be rounded and made smooth to prevent g-oug ing and removal of wax. A polyvinylidene chloride lm wrapper over the top of the dish may be used in place of the weighing cover.
|Organization:||Pulp and Paper Technical Association of Canada, Formerly CPPA|
|Change Type:||COMPLETE REVISION|
|Most Recent Revision:||YES|
|Document #||Change Type||Update Date||Revision||Status|
|D.15P||Change Type: STCH||Update Date: 2000-09-01||Status: INAC|
|D.15P||Change Type:||Update Date: 1980-01-01||Status: INAC|