GB/T 39500-2020 in English
VALIDLeather—Physical and mechanical tests—Determination of apparent density and mass per unit area
- Issued on:2020-11-19
- Implemented on:2021-06-01
- File Format:PDF
- Delivery:Via email within 1~3 business days
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《GB/T 39500-2020皮革 物理和机械试验 视密度和单位面积质量的测定》由TC252（全国皮革工业标准化技术委员会）归口，主管部门为中国轻工业联合会。
Introduction
Analysis of the core content of the standard
This standard modification adopts the ISO2420:2017 international standard, which mainly stipulates the use specifications of instruments such as die cutters and thickness gauges. By measuring the geometric dimensions and quality parameters of leather samples, the two key indicators of apparent density (Da) and mass per unit area (ma) are calculated.
Key Technical Differences
| Difference Dimensions | ISO2420:2017 | GB/T39500-2020 |
|---|---|---|
| Reference Standards | ISO2418/2419/2589 | GB/T39364/QB/T2707/2709 |
| Instrument Accuracy | Analytical Balance 0.001g | Analytical Balance 0.0001g |
| Result Presentation | Accuracy not specified | Da is accurate to 0.01kg/m³ ma is accurate to 0.01g/m² |
Key steps of the test
1. Sample preparation
Use die cutter to cut 3 samples: round (diameter 70±1mm) or square (100±1mm×100±1mm), non-standard sampling should be noted in the report.
2. Thickness measurement
Use the four-point measurement method (center point + equilateral triangle distribution points), use the thickness gauge that complies with QB/T2709, and take the arithmetic mean as the thickness value.
3. Comparison of calculation formulas
| Indicator type | Circular specimen | Square specimen |
|---|---|---|
| Apparent density Da | 1.273×10⁶×m/(t×d²) | 10⁶×m/(t×a×b) |
| Unit area mass ma | 1.273×10⁶×m/d² | 10⁶×m/(a×b) |
Implementation suggestions
- Instrument calibration: Regularly calibrate the die knife size deviation (±1mm) and die knife size deviation (±1mm) and die knife size deviation (±1mm) class=instrument>Analytical balance accuracy (0.0001g)
- Environmental control: The test is carried out under standard atmosphere (20℃/65%RH, 23℃/50%RH or 27℃/65%RH)
- Data rounding: The final result is rounded according to GB/T8170, and Da and ma are both rounded to two decimal places
- Abnormal handling: When the diameter/side length error is greater than 0.5mm, re-sampling and testing should be carried out
Standard evolution analysis
This standard makes up for the shortcomings of the ISO original version in terms of practicality by refining the sample type (round/square), adding non-standard sampling instructions, and improving instrument accuracy. In particular, the apparent density unit is unified as kg/m³, which is in line with the internationally accepted measurement system, while the g/cm³ conversion instructions (1g/cm³=1000kg/m³) are retained, reflecting the compatibility of standard setting.
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