Test methods for gas permeability and gas transmittance coefficient of thin films and flakes

1.
Test standards: YBB 00082003, GB/T 1038, ASTM D1434, ISO 2556, ISO 15105-1, JIS K7126-A, GB/T 2918-1998, GB/T 6672-1986 2.
The volume
of the gas that passes through the specimen area at constant temperature and pressure difference in time when it is stable through.

The volume value under standard temperature and pressure is expressed as: cm3/m2·d·Pa
.

3.
The gas transmittance coefficient under constant temperature and pressure difference, when the steady transmission, the time through the specimen thickness, area of the gas volume
.

The volume value under standard temperature and pressure is expressed as: cm3·cm/cm2·s· Pa
。
4 Principles of plastic film or sheet separates the low-pressure chamber from the high-pressure chamber, the high-pressure chamber is filled with a test gas of about 105Pa, and the volume of the low-pressure chamber is known
.

After the test sealing, a vacuum pump is used to pump the low-pressure indoor air to a near zero value
.

Measuring the pressure increment in the low-pressure chamber with a manometer ΔP determines the amount of gas in time from the high-pressure chamber through the membrane (sheet) to the low-pressure chamber, but the initial stage
of the change in the gas transmission velocity over time should be excluded.

The gas transmittance and gas transmittance coefficient can be calculated by the computer with the instrument and output to a floppy disk or printed on the record paper, or calculated according to the measured value
.

5.
Test instrument GTR-V3 gas transmittance tester 5.
1 ventilation chamber is composed of
two parts.

When the specimen is loaded, the upper part is a high-pressure chamber for storing the test gas.


The lower part is a low-pressure chamber used to store the permeable gas and determine the pressure difference before and after the breathability process to calculate the gas transmission of the specimen
.

Both upper and lower sections are equipped with inlet and outlet tubes
for test gas.

The low-pressure chamber consists
of a test bench with a hole in the center and a perforated disc mounted in a cavity.

Depending on the amount of air permeable in the specimen, the volume of the hole in the lower part of the perforated disc varies
.

A piece of filter paper should be embedded between the specimen and the perforated disc to support the specimen during the test
.

5.
2 The high and low pressure chambers of the pressure measuring device shall have a pressure measuring device, and the accuracy of the low pressure chamber pressure measuring device shall not be less than 6Pa
.

5.
3 The vacuum pump should be able to make the pressure in the low pressure chamber not more than 10Pa
.

6 The specimen should be representative and should have no traces or visible defects
.

The specimens are generally round, the diameter of which depends on the instrument used, and each set of specimens
is at least 3.

The specimen should be placed in a dryer for more than 48h state adjustment or processed
according to the product standard in the environment of 23±2 specified in GB/T 2918.

7.
Test step 1, preparation of the sample: the high-barrier membrane samples are placed in a dry environment of 5 °C for 48 hours
.

2.
After removing the samples, 3 specimens with a diameter of 97 mm are cut from each sample
.

2.
Specimen clamping: apply a layer of vacuum grease to the outer surface of the test chamber to avoid grease being applied to the middle disc of the cavity cavity; 3.
After placing the filter paper on the disc in the test chamber, the 3 specimens that have been adjusted from the high barrier membrane are clamped on the 3 test chambers of the differential pressure gas permeation instrument, the specimen should be kept flat, there shall be no folds, gently press to make the specimen in good contact with the vacuum grease, and then use the test chamber clamping structure to clamp the specimen
.

3.
Use the temperature control device to adjust the test temperature to 5 °C and the relative humidity to 0% RH
.

4.
Open the equipment software, set the test parameters, and start the test
.

5.
The test parameters include control parameters (test mode, upper cavity blowing time, upper cavity pressure, test time, degassing time, etc.
) and specimen parameters (number, type, area, thickness, etc.
).


6.
End of test, data processing
.

7.
After the test is completed, the instrument automatically calculates and displays the test results 8.
Turn off the air source and power supply
.