GB/T 39370-2020Leather. Physical and mechanical tests. Determination of surface reflectance (English PDF)

7.1 (see 7.1);

Leather - Physical and Mechanical Tests -

Determination of Surface Reflectance

3.1 Diffuse Reflection

Diffuse reflection refers to a phenomenon, in which, light projected on a rough surface

is reflected in all directions.

[GB/T 13962-2009, Definition 2.45]

3.2 Diffuse Reflectance

Diffuse reflectance refers to the ratio of the flux diffusely reflected (3.1) in all

directions to the total incident flux.

6.1 Sampling

In accordance with the stipulations of GB/T 39364, conduct the sampling.

NOTE: when the surface of the specimen is subject to abrasion or major tensile

deformation, the test results might be affected.

6.2 Specimen Preparation

Cut the leather to be tested into a rectangle with a size about 300 mm  200 mm.

6.3 Specimen Conditioning

In accordance with the stipulations of QB/T 2707, conduct specimen conditioning for

at least 24 h.

7.1 Calibration of Spectrophotometer System

Set the spectrophotometer system (5.1) to the detection of reflected light. Within the

wavelength range of 400 nm ~ 1,000 nm, the detected diffuse reflectance of the white

reference substances (5.2) and the black reference substances (5.3) is respectively

100% and 0%.

NOTE: the calibration is performed before the start of each measurement and after the

last measurement after over 1 h. Respectively set the upper limit and the lower

limit through the white reference substances (5.2, with a diffuse reflectance of

100%) and the black reference substances (5.3, with a diffuse reflectance of 0%).

The setting of the lower limit may also be achieved by completely shielding the

light source of the modulator tube or turning off the light source.

7.2 Test of Specimen

Place the leather specimen, with the test surface facing upwards, on the platform;

place the integrating sphere flatwise on the test surface of the specimen; measure the

diffuse reflectance; record its diffuse reflectance at a wavelength of 900 nm. Change

the position of the integrating sphere on the test surface of the leather specimen;

measure at least 3 positions. The positions of measurement shall be distributed as

evenly as possible in the center of the sample.

If the difference in diffuse reflectance measured at different positions of the specimen

exceeds 10%, then, it shall be indicated in the test report.

Appendix B

(informative)

Instruments and Materials

B.1 Overview

The following instruments are confirmed to be effective for this Standard. Other suitable

instruments may also be used.

B.2 Spectrophotometer

The spectrophotometer (5.1) includes the following components:

---Ulbricht integrating sphere, with a diameter of 30 mm and a port diameter of 6

mm;

---Halogen light source, with a wavelength range of 360 nm ~ 1,700 nm;

---Visible light - near-infrared spectrophotometer, with a wavelength range of 400

nm ~ 1,100 nm;

---Optical fiber (with an inner diameter of 400 µm), suitable for near-infrared light

transmission; used to connect light source, integrating sphere and

spectrophotometer;

---White reference substances;

---The operating software and computer of the spectrophotometer.

NOTE: other spectrophotometers that can measure surface diffuse reflectance in the

near infrared, especially at a wavelength of 900 nm, may also be used.

B.3 White Reference Substances

The white reference substances (5.2) with a diffuse reflectance of more than 98%

within the wavelength range of 250 nm ~ 1,500 nm can be used. Generally speaking,

the white reference substances are stored in a metal box protected from light, so as to

prevent them from being damaged. Suitable white reference substances can be

purchased from the supplier of the spectrophotometer.

B.4 Black Reference Substances

The black reference substances (5.3) with a diffuse reflectance of lower than 2% within

the wavelength range of 250 nm ~ 1,500 nm can be used. Generally speaking, the

black reference substances are stored in a metal box protected from light, so as to

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