QB/T 2714-2018Leather -- Physical and mechanical tests -- Determination of flex resistance (English PDF)

1.2011 "Leather - Determination of flex resistance - Part 1.Flexometer method".

This international standard is based on the International Federation of Leather

Craftsmen and Chemists (IULTCS) standard IUP 20, Part 1.

This standard has undergone the following technical changes when adopting

5402-1.2011 according to the actual situation in our country.

- In the normative references, RE-WRITE the originally quoted ISO standard

to relevant Chinese standards;

- For ease of use, SPLIT the contents of 5.1 into 5.1 and 5.2; the subsequent

clause number is changed accordingly;

- In order to prevent incorrect understanding of the standard in use, DELETE

the reference "note" in 5.1;

- REMOVE the informative appendix A (Source of instruments).

Leather - Physical and mechanical tests -

Determination of flex resistance

3.0 mm.

4.1 Flex resistance testing machine

The flex resistance testing machine shall include the components specified in

4.1.1 to 4.1.3.

It is performed according to the provisions of QB/T 2706.

5.2 Preparation of specimens

According to the provisions of QB/T 2707, use a die knife (4.2) to cut at least 4

specimens from the grain surface for testing. Among them, the long sides of at

least 2 specimens are parallel to the ridge line; the long sides of at least 2

specimens are perpendicular to the ridge line.

5.3 Air conditioning of dry specimen

Dry specimens shall be air-conditioned in accordance with the provisions of

QB/T 2707.

5.4 Preparation of wet specimen

Place the specimen in the glass dish (4.7). Add distilled or deionized water to

the glass dish at a depth of not less than 10 mm. Put the glass dish in the dryer.

Vacuum the dryer and maintain the vacuum degree at 4 kPa for 2 min. Then

release. Repeat the process of vacuum and release twice. Take out the

specimen. Use absorbent paper to absorb excess water. Immediately conduct

a wet test.

Note. The upper fixture cannot clamp a thicker specimen. In this case, the thickness of

one end of the specimen can be thinned to 1.5 mm and this end is inserted into the

upper fixture. Leather that is too hard shall not be tested using this method.

6.1 Open the upper and lower fixtures (4.1.1 and 4.1.2), so that the space in

the fixture is at least twice the thickness of the specimen.

6.2 Start the motor so that the EF side of the upper fixtures (4.1.1) is parallel to

the upper side of the lower fixtures [see Figure 2c)].

6.3 Fold the test surface of the specimen inwards so that the two long sides are

together. Clamp the folded specimen [see Figure 2a)], so that the folded side is

next to the lower side of the upper fixture; meanwhile one end is close to the

tighten screw of the upper fixture.

6.4 Make the two corners of the specimen that are not clamped wrap the fixture

outwards and downwards [see Figure 2b)], so that the two surfaces of the

specimen in contact. Fix the free end of the specimen in the lower fixture [see

Figure 2c)], meanwhile make it stretch vertically. The force used shall not

exceed the force required to just tighten the leather.

6.5 The required number of flex resistance can be selected from the following

The damage descriptions shall include the following.

- Change in color of the coating when there is no damage;

- Cracks in the coating, as well as the tendency of the cracks to extend to

one or more coatings; if possible, the number of cracks shall be recorded;

- Abnormal changes in the adhesion of the leather coating;

- Abnormal changes in adhesion between the two coatings;

- The powdering or flaking conditions of coating;

- The color contrast of cracks, powder or flakes on the coating.

If it needs to determine the degree of looseness of the leather structure, it can

cut the flexure part.

Note. Since the specimen is damaged after cutting, the subsequent test cannot be

carried out, so it can be cut after the final test is completed.

6.7 If the specimen needs to be taken out for observation during the test,

appropriate marking shall be made at the position where the specimen is

clamped, to ensure that the specimen can be fixed in the initial position when it

is put back.

6.8 Restart the testing machine to continue the test to reach the number of

times required. Repeat the inspection in 6.6.

6.9 If it needs to continue the test for another number of times, repeat steps 6.7

and 6.8.

Note. The choice of actual revolutions depends on the specified requirements, the final

use of the leather and the expected performance.

6.10 If only one test specimen is slightly damaged in the final inspection, repeat

the test for at least 4 specimens. If all the re-tested specimens are not damaged,

the final result is reported as "no damage"; otherwise the report shall record the

specimen of most serious damage.