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This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 22889-2008 Leather — Physical and mechanical tests — Determination of surface coating thickness. In addition to editorial changes, the following main technical changes have been made with respect to GB/T 22889-2008:
——The expression of results in “Principle” has been modified (see Clause 3 herein; Clause 3 of 2008 Edition);
——The requirements for microscope have been modified (see 4.1 herein; 4.1 of 2008 Edition);
——Apparatuses such as blades, grids and coating devices have been added (see 4.2 ~ 4.5);
——Scalpel, tissue slicer, micrometer and other apparatuses have been deleted (see 4.2 ~ 4.4 of 2008 Edition);
——The method of sample preparation has been modified and refined (see 5.3 herein; 5.3 ~ 5.4 of 2008 Edition);
——Optional measurement methods have been added into the test procedures and the test operation have been refined (see Clause 6 herein; Clause 6 of 2008 Edition);
——The test report has been adjusted (see Clause 8 herein; Clause 8 of 2008 Edition);
This standard has been redrafted and modified in relation to ISO 17186:2011 Leather — Physical and mechanical tests — Determination of surface coating thickness.
The following structural adjustments have been made with respect to ISO 17186:2011 Leather — Physical and mechanical tests — Determination of surface coating thickness.
——Subclause 5.1 has been divided into "5.1 Sampling" and "5.2 Air conditioning", with the following clause and subclause numbers arranged in sequence (see 5.1 and 5.2);
——Subclauses 5.2 and 5.3 have been combined into “5.3 Sample preparation" (see 5.3).
The technical differences of this standard from ISO 17186:2011 and their justifications are as follows:
——The adjustments on technical differences are made for the normative references of this standard to adapt to the technical documents in China, which are mainly reflected in Clause 2 "Normative references”, with the following specific contents:
? ISO 2418 has been replaced by GB/T 39364, which is modified in relation to the international standard (see 5.1 and Clause 8);
? ISO 2419 has been replaced by QB/T 2707, which is modified in relation to the international standard (see 5.2);
——The optional tool of blades has been added, which conforms to the current situation of leather industry and broadens the optional of cutting tools (see 4.2);
——The requirements for sampling of non-standard parts have been added to meet the needs of daily inspection (or sampling directly from shoes and clothing) (see 5.1);
——The size requirements of sample preparation have been modified, which conforms to the current industry practices, enhances operability and does not affect the test results (see 5.3);
——The description of confidence interval in measurement principle and method A has been deleted, so as to maintain the context consistency of the standard (see ISO 17186:2011, 6.1.1);
——The marking of measuring points in Figure 1 has been added to facilitate the understanding and use of this standard (see Figure 1);
—— The requirement for total distance between six equidistant measuring points in Method A have been added to enhance the accuracy of the results (see 6.2.1.5 and 6.2.2.4);
——The requirements for the accuracy of calculation results have been added, which conforms to our country's practices and enhances the comparability of results among laboratories (see Clause 7).
For the convenience of application, the following editorial modifications are made in this standard:
——Part of the content in "1 Scope" has been adjusted to the note in "3 Principle" (see Clause 3);
——The description method of microscope fitted with a graduated scale has been modified (see 4.1);
——Subclause titles to "5 Sampling and sample preparation” have been added (see Clause 5);
——The number of equation has been added (see 6.2.1.9 and Clause 7);
——The description of 6.2.2.8 and 6.3.3.8 has been simplified (see 6.2.2.8 and 6.3.3.8);
——The letter symbol and description of the results have added in the equation (see Clause 7);
——The order of test reports and the description of sample conditioning have been adjusted (see Clause 8).
This standard was proposed by the China National Light Industry Council.
This standard is under the jurisdiction of the National Technical Committee on Leather of Standardization Administration of China (SAC/TC 252).
The previous edition of this standard is as follows:
——GB/T 22889-2008.
Leather — Physical and mechanical tests — Determination of surface coating thickness
1 Scope
This standard specifies a method for determining the thickness of the surface coating applied to leather.
It is applicable to all types of leather.
2 Normative references
The following referenced documents are indispensable for the application of this standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced documents (including any amendments) applies.
GB/T 39364 Leather — Chemical, physical, mechanical and fastness tests — Sampling location (GB/T 39364-2020, ISO 2418:2017, MOD)
QB/T 2707 Leather — Physical and mechanical tests — Sample preparation and conditioning (QB/T 2707-2018, ISO 2419:2012, MOD)
3 Principle
A section of leather is taken perpendicular to the coated surface. The thickness of the surface coating is measured using a microscope and expressed both as a thickness and as a percentage of the total thickness.
Note: This method is used to determine the thickness of surface coating of leather when measured under zero compression.
4 Apparatus
4.1 Light microscope or scanning electron microscope, which can be operated with an object-field size of 1 mm × 1 mm, or lower, and is:
——fitted with a camera-image unit connected to a computer (resolution of at least 500 × 500 pixels), or;
——fitted with a photographical unit, or;
——equipped with an eyepiece with a graduated scale (at least 100 scale marks).
Note: 100 scale marks correspond to a scaling of 10 μm in the object-field dimension for an object-field size of 1 mm × 1 mm.
For measurement of coating thicknesses of less than 50 μm, an object-field size of 0.4 mm × 0.4 mm or lower has to be used. For measurement of values of less than 15 μm, a scanning electron microscope with a suitable object-field dimension should be used.
4.2 Razor blade, or other similar sharp tools.
4.3 Grid or similar calibration device, reading to at least 10 μm and suitable for use in the light microscope or scanning electron microscope.
4.4 Coating unit, using sputter or evaporation, including a suitable element or alloy (e.g. gold) for coating, if a scanning electron microscope is used.
4.5 Specimen stubs, suitable for a scanning electron microscope.
5 Sampling and sample preparation
5.1 Sampling
Sample in accordance with GB/T 39364. If it is not possible to take samples from standard parts (such as shoes and clothing directly), representative samples shall be taken from any parts within the available area, which shall be indicated in the test report.
5.2 Air conditioning
Condition in accordance with QB/T 2707.
5.3 Sample preparation
Cut three test pieces of approximately 10-mm length. Place the cutting edge of the razor blade (4.2) on the flesh side, with the blade perpendicular to the leather surface, and press the blade through the whole thickness of the leather, ensuring that the blade remains vertical. It is recommended that a new razor blade be used for each section.
If there is a requirement for more than two hides or skins to be tested in one batch, then only one test piece need be taken from each hide or skin, provided that the overall total is not less than three pieces.
If using a scanning electron microscope, stick a section prepared as described above onto a specimen stub (4.5) with the cut surface uppermost. Coat the stub and section in the coating unit (4.4) so that a sufficient image quality can be obtained.
6 Procedure
6.1 General descriptions
6.1.1 Principles of measurement
This standard describes two basic principles to measure the surface coating thickness.
Method A is based on the measurement of a number of values on equidistant positions (see Figure 1). It enables the determination of a standard deviation.
Method B is based on a measurement using parallel lines (see Figure 2). A statistical evaluation of the results is not possible due to the fact that the operator has to position the graduation of the grid between peaks and troughs manually. This process already includes a calculation of the average.
Method A should be preferred.
Methods A and B can be used for light microscopes as well as for scanning electron microscopes. The working distance and the acceleration voltage of the scanning electron microscope shall be the same for calibration and measurement of the sample.
Foreword i
1 Scope
2 Normative references
3 Principle
4 Apparatus
5 Sampling and sample preparation
6 Procedure
7 Expression of results
