TEAR TESTS
Tear testing is imitative of some of the stresses leather and textiles are subjected to during use. They are frequently put under tension in both clothing and upholstery, and it would be of great detriment if the material were to tear easily when tension is applied to a nick or cut. The double edge tear and trouser tear are the most commonly-used tear test methods for leather; out of these methods, only the trouser tear is used for textile samples.
Single Edge Tear test
Single Edge Tear
Also known as the ‘trouser tear’ or ‘tongue tear’.
Example leather standard: ISO 3377-1.
Example textiles standard: ASTM D2261. The trouser tear is a simple test.
A rectangular sample is cut centrally up to about halfway along its length. The two ends are attached to Tensile Grips and a tear produced along the un-cut part of the length. The sample’s orientation with respect to the backbone, warp and weft directions should be recorded. The results of interest are the average and initial tear strength for each sample orientation.
Double Edge Tear test
Double Edge Tear
Also known as the ‘slot tear’ or the ‘Baumann tear’.
Example leather standard: ISO 3377-2.
In this method, a wide slot with tapered ends is cut in the centre of a rectangular test specimen. Grips are inserted into the slot, which is then pulled open using the Texture Analyser, causing the material to tear from the tapered ends of the slot. The test is stopped when the tear has propagated to the edges of the test specimen. The maximum force required to propagate the tear and the thickness of the test specimen are recorded. This method can be used with all types of leather, but is generally not used with any other type of material. The result is recorded along with information on whether the test pieces were cut parallel or perpendicular to the backbone.
ADHESIVE PEEL TESTS
T-Peel Test for leather adhesion
T-Peel Test for Leather Adhesion
Example leather standard: ISO 11339.
The quality of a shoe is determined by its construction, materials used and the manufacturing process of the adhesive joint. Adhesive joint manufacture takes into account the need for an adhesive capable of promoting adhesion of the selected materials.
The adhesion of this joint can be assessed by several different methods, including the T-joint peel. In this test, the two materials to be adhered have any necessary treatments applied. They are then joined using the T-joint configuration. Tensile Grips are then used to pull the joint apart, causing it to unpeel. The force required to unpeel the joint is recorded. The higher this force, the stronger the joint.
Illustration of a typical Leather Adhesion test
Test for Adhesion of Finish
Example leather standard: ISO 11644.
Leather finish can separate from the bulk during use. With finishes consisting of several layers, the separation may occur between the layers. E.g. between the pigmented layer and the base coat.
This method uses a Leather Adhesion Rig and measures the force to pull the leather away from its surface finish layer at an angle of 90 degrees - the finished side of part of a strip of leather is bonded to an adherent-plate by means of an adhesive film. Force is applied to the free end of the strip to peel the leather from the finish over a given distance, the finish layer remaining on the adherent-plate together with the film of adhesive. The force required is measured and reported as the adhesion value of the finish. The adhesives used in this method harden quickly and there is no time for them to penetrate even quite thin finishes unless the finish has open cracks in it.
Conclusion
Stable Micro Systems Texture Analysers have been used by leading companies in the leather and textiles industries as first class equipment to these industries for several decades. Mechanical testing is of paramount importance to ensuring high quality from raw materials to finished products, and every stage in between. The quality of novel or alternative materials can be ensured as a key stage in the Research and Development process, and that of traditional materials kept track of during Quality Control.
There is a Texture Analysis test for virtually any physical property. Contact Stable Micro Systems today to learn more about our full range of solutions.
For more information on how to measure texture, please visit the Texture Analysis Properties section on our website.
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