GB/T 39372-2020Leather - Physical and mechanical tests - Determination of percentage extension (English PDF)

Foreword

This Standard was drafted in accordance with the rules in GB/T 1.1-2009.

This Standard uses the re-drafting method in the modification and adoption of ISO

17236.2016 Leather - Physical and Mechanical Tests - Determination of Extension Set.

In comparison with ISO 17236:2016, this Standard has structural adjustments as follows.

---The content of the third paragraph of 5.2 is modified into the NOTE of 5.2, so as to comply with the habits of our country (see 5.2);

---The content of 8 c) about result expression is adjusted to "7 Result Expression" (see Chapter 7).

In comparison with ISO 17236:2016, the technical differences and the causes for these differences are as follows.

---In terms of Normative References, this Standard adjusts the technical differences, so as to adapt to the technical conditions of our country. The adjustments are intensively reflected in Chapter 2 "Normative References". The specific adjustments are as follows.

GB/T 39364, which modifies and adopts International standard, is used to replace ISO 2418 (see 5.1);

QB/T 2707, which modifies and adopts International standard, is used to replace ISO 2419 (see 4.3 and 5.3);

QB/T 2709, which modifies and adopts International standard, is used to replace ISO 2589 (see 4.2 and 5.4); The reference of ISO 7500-1 is deleted;

---In tensile machine, the accuracy level of tensile force recording device is modified (see 4.1);

---The instructions for the sampling of non-standard sites are added, so as to satisfy the demands of routine inspection (or sampling directly from shoes and clothing) (see 5.1);

---The stipulations of horizontal and longitudinal specimens are added to sampling and specimen preparation, so as to facilitate standard compilation and test results recording (see 5.2);

---The calculation formula is adjusted and the unit description of percentage extension is added, so as to comply with the habits of our country (see Chapter 7);

---The requirements for the accuracy of the calculation results are added, which enhances the comparability of results between laboratories (see Chapter 7);

---The test report is adjusted and the requirements for the accuracy of thickness are added, which enhances the comparability of results between laboratories (see Chapter 8). This Standard also makes the following editorial modifications.

---The title of this Standard is modified into. "Leather - Physical and Mechanical Tests - Determination of Percentage Extension";

---The description of the tensile machine in 4.1 is modified from two clauses into the itemized form (see 4.1);

---Clause titles are added to "5 Sampling and Specimen Preparation" (see Chapter 5).

4 Instruments and Equipment

4.3 Die cutter, which complies with the stipulations of QB/T 2707. The inner wall is a rectangle with a size of (250 ± 5) mm (10.0 ± 0.5) mm.

4.4 Scale ruler, with an accuracy of 0.5 mm.

4.5 Stopwatch, with an accuracy of 1 s.

4.2 Thickness gauge, which complies with the stipulations of QB/T 2709

5 Sampling and Specimen Preparation