The moisture permeable cup is used for the moisture permeability test of packaging materials such as paper, cardboard and plastic film.
Structure and working principle
Moisture-permeable cups are assembled from cups, cup rings, guide rings, glands, glasses, cup stands, etc., as shown in Figure 2-23. The materials required are light, corrosion-resistant, impervious to water, and airtight. Put the baked desiccant in the moisture-permeable cup, put the sample on the moisture-permeable cup, fix the position according to Figure 2-23(a), remove the guide ring, and pour melted wax into the cup In the ring groove of the ring and the moisture-permeable cup, the molten wax should cover the sample. After the wax is solidified, the sample, the moisture-permeable cup and the cup ring are solidified together, and the desiccant in the cup is separated from the atmosphere with the sample, weighed and put into the adjusted temperature and humidity control box. The desiccant in the cup continuously absorbs water vapor to reduce the air pressure, and has a constant temperature and humidity outside the cup, so that a vapor pressure difference is formed between the inside and outside of the cup. Under the action of the pressure difference, water vapor will pass through the sample continuously. The desiccant continuously absorbs water vapor, and after a certain period of time, the weight of the desiccant increases, and the moisture permeability of the sample can be calculated after weighing.
Figure 2-23 Moisture-permeable cup
1-gland; 2-cup ring; 3-cup; 4-guiding ring; 5-glass; 6-cup table;
7-sealing wax; 8-sample; 9-desiccant
The main technical parameters
a. Effective measurement area: not less than 25cm2.
b. Desiccant particle size: 1.6 ~ 4.0mm.
