Method for determining the folding strength at low temperature of different leathers أداة الاختبار –

Method for determining the folding strength at low temperature of different leathers

(1) Reference standard: \"QB/T 2714-2005 Physical and mechanical tests of leather - Determination of folding strength\".
(2) Test instrument: low temperature bending tester. Hengyu Low Temperature Leather Bending Tester is used to test the cold resistance of upper leather of shoes, synthetic leather, etc., allowing customers to fully understand the adaptability of materials or finished products to climates at low temperature or cold areas. , this machine is made of stainless steel and can be equipped with various heavy-duty brackets to meet different testing requirements.
　 (3) Test principle: According to the low temperature test conditions, the number of bends is selected according to the test requirements before the test begins. After the test is completed, stop the flower testing machinexion at low temperature, remove the sample, fold the sample upside down along the longitudinal axis and check and record any damage on the folded part to judge the folding resistance of the leather.
The upper test surface of the sample is bent and clamped in a movable holder, and the lower test surface is bent outward and clamped in a fixed holder. The upper movable device causes the sample to move, thereby inspecting defects caused by the sample.
(4) Test method: Fold the testing surface of the leather sample inward so that the two long sides are together, clamp the folded sample and extend it vertically into the support. The bending angle of the bracket is (22.5±0.5)°, the bending frequency is (100±5) times/min, and it will automatically stop after the experiment according to the preset number of flexions.
(5) Test data (Table 2):

　
From the above experimental results, it can be seen that at low temperatures, relatively soft leather, whether or not it is untreated natural leather, or thinner alternative leather and softer materials such as PU leather, have better resistance to folding when the temperature changes. On the contrary, even if the leather has been coated and treated, even if it is natural leather, the fiber bundles of the grain layer are more delicate and fragile than those of the mesh layer. As the temperature decreases, the grain layer often weakens from repeated flexing. If cracks appear first, the strength of the adhesion between the covering film and the leather body will also weaken under repeated bending, so cracks are more likely to occur. In summary, in low temperature environments, the impact of temperature on natural leather is not significant, while leather enduit is affected by low temperature environments and the material is prone to brittleness, resulting in varying degrees of failure. In the actual test, the quality of samples is also one of the important factors affecting the test results.

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