GB/T 39369-2020Leather - Physical and mechanical tests - Determination of water vapour permeability (English PDF)

4.1 Container bottle: the inner diameter of the bottleneck is (30+/-3) mm; it has a

swiveling cover that has a round hole; the diameter of the round hole is equal

to the inner diameter of the bottleneck; the bottle height is about 70 mm ~ 90

mm.

4.2 Tester, which includes the following parts:

a) Turntable: it is installed vertically; the speed is (75+/-5) r/min; it can support

the container bottle (4.1); the circular axis of the container bottle is parallel

to the axis of the turntable; the distance between the two axes is (67+/-2)

mm.

b) Fan: it is installed on the bottle mouth opposite to the container; it contains

4.3 Dry allochroic silica gel: the particle size is 2 mm ~ 5 mm; sift out smaller

particles and dust. Before the test, dry it in a ventilated oven at (125+/-5) °C for

about 16 h; then, cool to the test temperature in a closed container bottle. The

particle size of silica gel shall be such that it cannot pass through a 2-mm screen;

the desiccant that has not been cooled to the test temperature shall not be used.

Note 1: It is recommended to use silica gel beads, because compared with

silica gel particles, silica gel beads generate less dust.

Note 2: When a large amount of silica gel is placed in a closed container bottle,

the cooling rate is slow; the cooling time can be appropriately extended,

so as to cool all silica gel to the test temperature.

4.4 Analytical balance: the accuracy is 0.1 mg.

4.5 Timer: the accuracy is 1 min.

4.6 Caliper: the accuracy is 0.1 mm; it can measure the inner diameter of the

bottleneck of the container bottle.

4.7 Die cutter: in line with the provisions of QB/T 2707. It can cut a round sample

that matches the container bottle mouth, so that it has a better airtightness at

the container bottle mouth.

the leather during the sanding process is about 2 N (It can also be polished

with a suitable instrument). Then, use the die cutter (4.7) to cut a round

specimen in the area of the leather after sanding.

b) According to the provisions of QB/T 2714, bend the specimen 20 000 times;

use the die cutter (4.7) to cut a round specimen within the bent area.

c) Use the die cutter (4.7) to directly cut a round specimen.

Note 2: The coating of leather grain can affect the penetration of water vapour

into the leather; this effect will be reduced after a slight sanding or

bending test. The treatment methods which are specified in a) and b)

are intended to imitate the wear of leather in use. If the specimen does

not require pretreatment, directly use method c), which is more

suitable for suede leather or uncoated leather.

5.3 Adjustment of specimens

Adjust according to the provisions of QB/T 2707; test in standard atmosphere.

6.1 Put half a bottle of freshly-dried silica gel in the container bottle (4.1).

6.2 Place the specimen on the container bottle mouth, with the use side facing

out.

6.3 Cover the swiveling cover and tighten it, so as to fix the sample and keep

the container bottle tightly sealed at the edge.

Note: If necessary, heat the container bottle appropriately, and apply a thin layer

of beeswax (4.8) to the bottleneck, so as to seal the specimen and the

bottleneck. If using beeswax to seal, heat the container bottle to (50 +/-

5) °C before putting the silica gel and the sample.

6.4 Place the container bottle on the turntable and start the instrument.

Note: Additional containers and bottles that are specified in 6.1 ~ 6.3 can be

used to ensure the balance of the turntable.

6.5 Use a caliper (4.6) to measure the inner diameter of the bottleneck of the

second container bottle in two mutually perpendicular directions, to the nearest

0.1 mm. Calculate the average of the diameters in the two directions as the

average inner diameter d of the bottleneck of the container.

6.6 After (20+/-4) h, remove the first container bottle as soon as possible. Put half

a bottle of freshly-dried silica gel in the second container bottle; remove the

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