he tensile properties of plastics and rubber are one of the most important and basic properties of their mechanical properties. It determines the use of this kind of plastics and rubber to a great extent. Tensile properties can be tested by tensile tests.
1, the tensile properties of high molecular polymers
Polymers are required to have necessary mechanical properties when used as materials. It can be said that for most applications of polymer, mechanical properties are more important than other physical properties.
The macromolecular polymer has the most wide mechanical properties in all known materials, because the polymer is composed of long chain molecules and the molecular motion has obvious relaxation characteristics. For example, high polymer material has a high elongation rate, the elongation at break of PE is 90% ~ 950% (and the elongation of linear low density polyethylene LLDPE is higher). Through special process, the elongation of some materials can be above 1000%, and the breaking elongation of ordinary polymer material is also between% to 100%. . Heat shrinkable films and stretching films are usually required for high tensile properties of materials.
2, tensile test
The tensile test (stress strain test) is generally used to clamp the two ends of the material on two fixtures at a certain distance, and the two fixture is separated and stretched at a certain speed, and the stress changes on the specimen are measured until the specimen is destroyed.
Tensile test is one of the most widely used methods to study the mechanical strength of materials. It needs constant speed tensile testing machine. According to the different methods of load measurement, the tension test machine can be divided into two types: pendulum tension test machine and electronic tension test machine.
3. Selection index of electronic tensile test machine
Because the soft packaging material is mainly polymer or its related materials, the elongation of the polymer material is far superior to the metal, fiber, wood, plate and other materials. Therefore, the tensile machine testing high molecular polymer has some difference with the tensile testing machine of the usual material. It is the effective travel of the electronic tension machine and the two aspects of the sample fixture.
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