This standard specifies the method for determining the moisture permeability and crease moisture permeability of paper and paperboard. This standard is applicable to paper and paperboard and other thin materials with a thickness of less than 3 mm. GB/T 2679.2-1995 Determination of moisture permeability and crease moisture permeability of paper and paperboard (disc method) GB/T2679.2-1995 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Paper and board-Determination of water vapour transmission rate and crease moisture permeability (Dish method)
Paper and board-Determination of water vapour transmission rate (Dish method) This standard adopts the international standard ISO2528-1974 (Edition 1) "Thin sheet materials-1 Subject content and scope of application
This standard specifies the method for determining the water vapour transmission rate and crease moisture permeability of paper and board. This standard is applicable to paper, board and other thin sheet materials with a thickness of less than 3mm. 2 Reference standards
GB/T450--89 Paper and board sample sampling GB/T10739-89 Standard atmosphere for handling and testing of pulp, paper and board samples 3 Terminology
GB/T 2679.2-1995
Replaces GB 2679.2--81
-Determination of water vapour transmission rate-
Dish method".
3.1 Moisture permeability The two sides of the paper or cardboard maintain a certain vapor pressure difference, and water vapor permeates from one side of the sample to the other side, which is expressed as the mass of water vapor that permeates 1 m2 of the sample in 24 hours (g/24h·m2). The moisture permeability depends on the thickness of the material, the anti-permeability of the material components and the temperature and humidity conditions of the test.
3.2 Crease moisture permeability Under the same test conditions as the moisture permeability, the difference between the moisture permeability of the creased test piece and the moisture permeability of the uncreased test piece is expressed as the mass of water vapor that permeates the crease of the 100m long sample in 24 hours (g/24h·100m). 4 Instruments and materials
4.1 Constant humidity and constant temperature box: The temperature can be accurately controlled within the range of ±0.5℃, the relative humidity can be accurately controlled within the range of 2%r·h, the wind speed is 0.5~2.5m/s, and the specified temperature and humidity should be reached within 15min after the box door is closed. 4.2 Moisture permeability cup: As shown in Figures 1 and 2, it consists of a cup and a cup ring. The permeable cup is made of impermeable and corrosion-resistant materials, and the effective test area of ​​the cup is 0.00283m2.
Figure 1 Cup ring
Approved by the State Administration of Technical Supervision on July 6, 1995o
Figure 2 Cup
Note: Permeable cups with a diameter greater than d60 mm can also be used. Implementation on April 1, 1996
GB/T 2679.2-—1995
4.3 Wax sealing positioner: As shown in Figures 3 to 5, it consists of a guide ring, a cup stand and a pressure cover. @102
Figure 3 Guide ring
Figure 5 Pressure cover
4.4 Metal pressure roller: 6.5cm wide, 6.5kg heavy, used when making crease specimens. 10
Figure 4 Cup table
4.5 Analytical balance, precision 0.1mg.
4.6 Wax for sealing: industrial paraffin or other wax that does not soften at 38℃ and whose mass change in 24h is not more than 1mg under the condition of 50cm2 exposure area.
4.7 Desiccant: anhydrous calcium chloride with a particle size of passing through a 2.4mm sieve hole but not passing through a 0.6mm sieve hole or silica gel with a particle size of not more than 5mm after drying at 120℃ for more than 3h.
5 Sample collection, preparation and treatment
5.1 Sample collection shall be carried out in accordance with GB/T450. Four samples with a diameter of 64mm are cut uniformly along the transverse direction of the paper web. If the moisture permeability of the fold is measured, four more samples are cut from the adjacent longitudinal parts of the sample taken, and the front and back sides of the samples taken are marked. 5.2 Treat the 4 samples of moisture permeability with creases in the standard atmosphere specified in GB/T10739 for 4 hours, then gently fold the sample in half and place it on a flat glass plate, and roll it back and forth with a metal roller with a mass of 6.5 kg once each (the fold line is parallel to the axis of the roller during rolling), unfold the sample after rolling and use the roller to flatten the crease. Use the same method to make a second crease in the direction perpendicular to the first crease (note that the two folds should face different sides of the paper surface), so as to make a sample with creases. 6 Test steps www.bzxz.net
6.1 Add desiccant to the moisture permeability cup, make the desiccant surface flat, and keep a distance of about 3mm from the bottom of the sample. Then place the sample on the cup mouth with the paper side facing the dry side in use, otherwise place half of it with the front side facing down and half with the back side facing down. Place the cup ring on the sample facing the cup mouth, and press the cup ring properly through the positioning device shown in Figure 6. 562
GB/T 2679.2-1995
Figure 6 Assembly diagram of the sample sealing positioning device
6.2 Slowly pour the molten paraffin heated to 90-100℃ in a water bath into the wax groove of the permeable cup. The qualified sealing wax will be in a crescent shape after cooling. If there are bubbles or slight cracks, they can be trimmed with a hot scraper. If the temperature of the molten wax is too high, it may cause more bubbles or cracks. Such samples should be abandoned.
6.3 Number the permeable cups with sealed samples and cover them with lids of the same number. Then weigh them with a rough balance for the convenience of subsequent accurate weighing (this operation can be omitted if an electronic fast balance is used). Then remove the lid (the lid should be stored on a sealed shelf) and put the permeable cups into a constant humidity and constant temperature box with a humidity of (90±2)% r·h and a temperature of 38±0.5℃ for pretreatment for 2 hours. 6.4 Take the permeable cup out of the constant humidity and constant temperature box, cover it with the corresponding lid, place it near the balance for 15 minutes, and then start weighing, accurate to 0.1mg. After all weighing is completed, remove the lid and immediately put it back into the constant humidity and constant temperature box. Start timing when it reaches (90±2)%r·h and 38±0.5℃.
6.5 Weighing can also be done without a lid, but the transfer and cooling of the permeable cup should be carried out in a dryer equipped with a moisture absorbent. 6.6 Weigh the permeable cup once every certain time interval (repeat the operation of 6.4) until the change in the mass increase of the permeable cup between two consecutive weighings is less than 5%, and terminate the test. The average of these two results is used to calculate the moisture permeability. 6.7 When the moisture permeability of the sample is higher than 50g/24h·m2, the method of calculating the moisture permeability by the mass change in the first test cycle can be used.
6.8 Each weighing should be carried out under the same atmospheric conditions, and the weighing order of each permeable cup should be consistent. The time interval between two weighings is generally 24h, but can also be 48h or 96h. For samples with excessive moisture permeability, 4.8h or 12h can also be used. However, the mass increase of the moisture permeable cup between two consecutive weighings should not be less than 5mg.
6.9 For samples with extremely low moisture permeability, the mass may not change in the first few days. In this case, the test period should be extended to start timing when the mass increases. If the mass of the moisture permeable cup does not increase within seven days, the test can be terminated and the sample is reported to be non-permeable. 6.10 Before the end of all tests, the mass increase of the desiccant should be controlled to be no more than 10% for calcium chloride and no more than 4% for silica gel. 7 Calculation and expression of test results
7.1 Moisture permeability is calculated according to formula (1):
Where: P——moisture permeability, g/24h·m2W,—mass increase of the moisture permeable cup of the uncreased sample, g; A-—effective area of ​​the moisture permeable cup, m\;
T→time between two weighings, h.
7.2 The average crease moisture permeability is calculated according to formula (2): (1)
Wherein: CP
GB/T 2679.2—1995
(W2- W) × 2 400
CP=,
Average crease moisture permeability, g/24h?100m; Increase in mass of the moisture permeability cup of the uncreased sample, g, Increase in mass of the moisture permeability cup of the creased sample, g; W.
D-—Effective diameter of the moisture permeability cup, m;
T-—Time interval between two weighings, h.
7.3 The calculated result is rounded to two significant figures. Test precision
The repeatability of this test is 8.1%, and the reproducibility is 23%. 9 Test report
The test report shall include the following contents:
National Standard Number:
Information on comprehensive identification of the sample;
Test conditions;
Measured moisture permeability or crease moisture permeability; Any operation that deviates from the provisions of this standard. Additional remarks:
This standard was proposed by the China Light Industry General Association.
This standard is under the jurisdiction of the National Technical Committee for Standardization of Paper Industry. This standard was drafted by Tianjin Paper Research Institute. The main drafters of this standard are Zhang Xu, Zhang Xiaoqi, Hou Junling and Liang Shuqin. 564
(2)
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