Help you choose an electronic tension testing machine based on mechanical properties

The tensile properties of plastics and rubber are one of the important and basic properties of their mechanical properties, which largely determines the use of this type of plastics and rubber. The quality of tensile performance can be detected by an electronic tensile testing machine.

1. Tensile properties of polymers. When used as materials, polymers are required to have the necessary mechanical properties. It can be said that for most applications of polymers, mechanical properties are more important than other physical properties. Polymer polymers have mechanical properties with a wide range of variability in all known materials, because polymers are composed of long chain molecules and molecular motion has obvious relaxation properties. For example, polymer materials have a very high elongation, and the elongation of breakage of PE is generally between 90% and 950% (of which linear low-density polyethylene LLDPE is relatively high). Through special production processes, the elongation of some materials can be above 1000%, while the elongation of breakage of ordinary polymer materials is usually between 50% and 100%. Generally, heat shrink films and stretch films require high tensile properties of materials.

2. Tensile test Tensile test (stress-strain test) generally clamps the two ends of the material sample on two fixtures at a certain distance, and separates and stretches the sample at a certain speed to measure the stress changes on the sample until the sample is damaged. Tensile test is one of the widely used methods to study the mechanical strength of materials, and a tensile test machine with constant speed movement is required. According to the different load measurement methods, tensile testing machines can be roughly divided into two categories: pendulum tensile testing machines and electronic tensile testing machines. Currently, the most commonly used electronic tensile testing machines are used.

3. Selection indicators of electronic tensile testing machine. The elongation of polymer polymers or related materials, as mentioned above, is much better than that of metals, fibers, wood, boards and other materials. Therefore, the tensile machine for detecting polymer polymers is different from the tensile performance detection machine of the usual material. It is especially important to pay attention to the effective stroke of the electronic tensile machine and the sample fixture.

3.1 Effective stroke When conducting tensile tests, although the size of the sample used is small, the elongation of the material is generally relatively high. Therefore, when used to detect the tensile performance of flexible packaging materials, it is necessary to be equipped with a tensile machine with a large stroke, otherwise the operation of the fixture may exceed the stroke limit and cause damage to the equipment. It should be noted that in the calculation of elongation, we only collect the elongation between the two markers on the sample. The markings are drawn on the finished sample by printing or manual printing (the addition of markings should have no effect on the sample), and what is the distance between markings? The distance given by different standards mostly has certain differences, and in the same standard, different sample sizes are often given for different materials, so the distance between markings is also different. However, this is conducive to detecting materials with very large or very small elongation and obtaining accurate test results. For plastic films, the distance between the markings is usually between 25 and 50 mm. Since the sample is deformed and elongated in the tensile test is not only within the markings, any sample between the two fixtures will be tensile deformation to varying degrees. In the standard, the initial distance between the fixtures corresponding to the marking distance is within 80-115 mm. If the samples between the two fixtures can maintain the same elongation and assume that it is 500%, the effective stroke of the tensioning machine must be 480-690 mm. If it is a sample with an elongation of 1000%, the effective stroke of the tensioning machine is at least 880 mm to ensure the normal progress of the test.