GB/T 47492-2026Sanitary paper products - Determination of air and moisture permeability (English PDF)

4.1 Principle of air permeability test

4.1.1 Horizontal air permeability The sample is placed between a test plate and a test head with a vent at the bottom. A certain pressure is applied to the upper part of the test head to make the test... The bottom surface of the test head contacts the sample under a certain pressure. Under specified test conditions, the time it takes for a certain volume of compressed air to pass through the sample is used to represent the pressure. Its horizontal breathability is demonstrated.

4.1.2 Vertical air permeability The sample is placed between a test plate with a circular air vent and a hollow test cup with a circular bottom. The upper part of the test cup... Pressure is applied to press the bottom of the test cup tightly against the surface of the sample, forming a sealed cavity inside the test cup. Under specified test conditions, the contents of the test cup... The time required for compressed air to pass vertically through a specimen of a specified area is used to characterize its vertical permeability.

4.2 Principle of Dry-State Moisture Permeability Test The dry sample is placed on a moisture permeability test plate, then positioned between the upper and lower test chambers, and sealed by applying pressure. The sample will then be tested. The cavity is divided into two sealed chambers. Under the action of the temperature and humidity control device, a humidity difference is created between the two sealed chambers. Within a specified time, the temperature and humidity are adjusted to maintain a high humidity level. The mass of water vapor penetrating the sample into the low-humidity cavity characterizes its dry-state moisture permeability.

5.1.1 Horizontal air permeability tester

5.1.1.1 The horizontal air permeability tester, as shown in Figure 1, mainly consists of a horizontal air permeability test plate, a test head, a pressure sensor, and an air storage device. It consists of ball valves, timing devices, etc.

5.1.1.2 Horizontal air permeability test plate. used to lay and fix the sample flat, and the surface should be flat.

5.1.1.3 Test Head. The bottom is made of circular silicone material, with the bottom area of the circular silicone material being (20.0±0.1) cm^2, (38.0±0.2) cm^2, and... (64.0±0.2)cm2 in three specifications.

5.1.1.4 Gas storage device. can provide a certain volume of compressed air, with a pressure bearing capacity >=10kPa and a volume of (30.0±0.5)L.

5.1.1.5 Pressure sensor. range 0 kPa~40 kPa, accuracy 0.075%FS.

5.1.1.6 Timing device. accuracy is ±0.1s.

5.1.2 Vertical air permeability tester

5.1.2.1 The vertical air permeability tester, as shown in Figure 2, mainly consists of a vertical air permeability test plate, a test cup, a pressure sensor, and an air storage device. It consists of ball valves, timing devices, etc.

5.1.2.2 Vertical air permeability test plate. Used to lay and fix the sample flat; the surface should be flat. The test plate should have a circular air permeability in the center. The vent area is available in three specifications. (5.0±0.1)cm2, (20.0±0.1)cm2, and (50.0±0.2)cm2.

5.1.2.3 Test cup. The inside is a hollow cavity with an internal volume of (300±10) mL, and it is generally made of 304 stainless steel or similar material.

5.1.2.4 Gas storage device. can provide a certain volume of compressed air, with a pressure bearing capacity of >=10kPa and a volume of (30.0±0.5)L.

5.1.2.5 Pressure sensor. range 0 kPa~40 kPa, accuracy 0.075%FS.

5.1.2.6 Timing device. accuracy is ±0.1s.

5.1.2.7 Combed pure cotton plain knit fabric. yarn linear density of 16tex~18tex, unit area mass of 120g/m2~ 140g/m^2, length (120±5)mm, width (65±2)mm. Combed pure cotton weft-knitted fabric with an air permeability >=700mm/s. According to GB/T 5453, the test area is 20 cm2 and the pressure difference is 100 Pa.

5.2 Dry-state moisture permeability tester

5.2.1 The dry-state moisture permeability tester, as shown in Figure 3, mainly consists of a dry-state moisture permeability test plate, a low-humidity chamber, a high-humidity chamber, and a temperature and humidity control device. It consists of a flow meter, a circulating pump, a desiccant, a timing device, etc.

5.2.2 Dry-state moisture permeability test plate. Used to lay and fix the sample flat; the surface should be flat. There is a circular moisture permeability hole in the center of the test plate. The area is available in three specifications. (5.0±0.1)cm2, (20.0±0.1)cm2, and (50.0±0.2)cm2.

5.2.3 Test Chamber. Includes a low-humidity chamber and a high-humidity chamber, mainly providing a specific temperature and humidity environment for sample testing. The sample and the test chamber should be tightly sealed. It must be sealed well to ensure it is airtight and moisture-proof.

5.2.4 Temperature and Humidity Control Device. The device should include temperature and humidity sensors, with a temperature control accuracy of ±2°C. Relative humidity control accuracy... For ±3%, the device should have a continuous and stable circulating airflow, and the temperature and humidity within the test space should be uniform. During the test, the sample surface... Condensation should not occur.

5.2.5 Desiccant. The main component is molecular sieve, with a particle size of 1.6mm~2.5mm. Static temperature is measured at 25°C using saturated saline solution. Water adsorption capacity >=30%, and tapped bulk density between

0.64 g/mL and

0.68 g/mL.

5.2.6 Circulation pump. Provides a stable circulating airflow and should not cause changes in humidity in the pipeline during the circulation process.

5.2.7 Flow meter. test range 0L/min~5.0L/min, accuracy 0.5%FS.

5.2.8 Timing device. accuracy is ±0.1s.

5.3 Electronic Balance The graduation value is 0.01g.

7.1 Horizontal air permeability test procedure

7.1.1 After the temperature and humidity treatment, lay the sample flat on a horizontal air permeability test plate with the top surface facing upwards. During the test, the sample surface should be flat. The sample should be neat and free of obvious wrinkles. If the sample is a pair of trousers, cut the elastic band with scissors.

7.1.2 Based on the sample type and core width, select a suitable test head and place it at the test position on the sample surface, ensuring the test head is positioned correctly on the sample. Within the core width. Apply pressure to the upper end of the test head so that the pressure at the contact surface between the bottom surface of the test head and the sample reaches (4.0±0.2) kPa, or according to... Select test heads with other pressures or different areas for the sample type and size.

7.1.3 During the test preparation phase, compressed air is introduced into the gas storage device to make the gas pressure inside the gas storage device reach above

7.1.4 When the gas pressure in the gas storage device drops to

1.21 kPa, the test shall be started immediately, and the timing device shall start timing simultaneously. When the gas pressure... When the pressure drops to

0.11 kPa, the timing device stops timing and records the test time.

7.1.5 Perform tests at three different locations-the middle and both ends-of the absorber core of the sample, following the above procedure. The minimum test value represents the value of the sample. If the horizontal permeability time of the sample is insufficient to test at three different locations, the number of test points can be appropriately reduced, and this should be stated in the report. illustrate.

Note. The horizontal breathability test is not applicable to sanitary napkins (panty liners).

7.2 Vertical air permeability test procedure

7.2.1 Select a suitable vertical air permeability test plate according to the sample type and core width, ensuring that the diameter of the air permeability pores in the test plate is small. The width of the sample core.

7.2.2 After the temperature and humidity treatment, lay the sample flat on a vertical air permeability test plate with the top surface facing upwards. During the test, the sample surface should be flat. The sample should be clean and free of obvious wrinkles. If the sample is a pair of pants, cut the elastic band with scissors. If the sample is a sanitary napkin, remove the release liner before testing. The material is then pasted with combed pure cotton weft-knitted fabric (5.1.2.7), and then laid flat on a vertical air permeability test plate for testing.

7.2.3 Select the appropriate test cup and press it firmly onto the test position of the sample surface to achieve a sealing effect. The test cup should completely cover the sample core. width.

7.2.4 During the test preparation phase, compressed air is introduced into the gas storage device to make the gas pressure inside the gas storage device reach above

7.2.5 When the gas pressure inside the gas storage device drops to

1.21 kPa, the test is started, and the timing device starts timing simultaneously. The test continues until the gas pressure drops further. When the pressure drops to

0.11 kPa, the timing device stops timing and records the vertical air permeability test time.

7.2.6 Following the above procedure, test at three different locations. the middle and both ends of the absorber core of the sample. The minimum test value represents the value of the sample. If the vertical permeability time of the sample is insufficient to test at three different locations, the number of test points can be appropriately reduced, and this should be stated in the report. illustrate.

7.3 Dry-state moisture permeability test procedure

7.3.1 Select a suitable moisture permeability test plate according to the sample type and core width, ensuring that the diameter of the moisture permeability pores in the test plate is smaller than that of the sample. Core width.

7.3.2 Remove the balanced sample from the sealed bag. If the sample is a sanitary napkin product, the release material needs to be removed before testing. Then flatten the sample. Lay the sample on a moisture permeability test plate with the top layer facing down. The sample surface should be flat and free of obvious wrinkles during testing. If the sample is trousers, use scissors. Cut the elastic band.

7.3.3 Place the test plate with the sample laid on it in the middle of the upper and lower test chambers, ensuring the test chambers cover the absorbent core of the sample. The test chamber is divided into two chambers. the chamber in surface contact is the high-humidity chamber, and the other side is the low-humidity chamber. There should be a tight seal between the test chamber and the test plate. It is well-sealed, airtight, and moisture-proof.

7.3.4 The temperature and humidity control device pre-treats the water vapor remaining in the low humidity chamber until the relative humidity in the low humidity chamber is adjusted to 15%. Next, adjust the temperature and humidity inside the high humidity chamber to control the temperature within (35±2)°C and stabilize the relative humidity at (85±2)°C. Within 5)%.

7.3.5 Connect approximately 100g of desiccant (of known mass M1) to the circulation line. Start the test; the timing device in the instrument will begin counting. At the same time, the circulation pump is turned on to control the relative humidity in the low humidity chamber to be maintained within the range of (15±5)%.

7.3.6 After 2 hours of timing, turn off the circulation pump and weigh the desiccant, recording the mass as M2, accurate to 0.01g. Environmental factors should be eliminated during the test. The effect of humidity on sample quality.