At present, there are many tensile testing machines on the market for testing the tensile properties of materials, but not all testing machines are suitable for tensile testing of flexible packaging materials. This paper analyzes the selection of tensile testing machines for flexible packaging materials in combination with my country’s material testing standards. indicators of particular concern.
The tensile properties of plastics and rubbers are one of the most important and basic properties in their mechanical properties, which to a large extent determine the use of such plastics and rubbers. The quality of tensile properties can be detected by tensile test.
- Tensile properties of polymers
When used as a material, high molecular 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.
High-molecular polymers have the widest range of variability among all known materials in mechanical properties. This is due to the fact that high-molecular polymers are composed of long-chain molecules, and molecular motion has obvious relaxation characteristics. For example, high polymer materials have quite high elongation, and the elongation at break of general PE is 90% to 950% (the elongation of linear low density polyethylene LLDPE is relatively high). The elongation at break can be above 1000%, while the elongation at break of ordinary high polymer materials is mostly between 50% and 100%. Generally, heat-shrinkable films and stretched films have higher requirements on the tensile properties of materials. - Tensile test
Tensile test (stress-strain test) generally clamps the two ends of the material sample on two fixtures with a certain distance apart, and the two fixtures separate and stretch the sample at a certain speed to measure the stress change on the sample. until the sample fails. the
Tensile testing is one of the most widely used methods to study the mechanical strength of materials, which requires the use of a constant-speed tensile testing machine. According to different load measurement methods, tensile testing machines can be roughly divided into pendulum impact testing machines and electronic tensile testing machines. At present, electronic tensile testing machines are more commonly used. - Selection index of electronic tensile testing machine
Since flexible packaging materials are mainly high molecular polymers or its related materials, as mentioned above, the elongation of high polymer materials is far superior to that of metal, fiber, wood, board and other materials, so the tensile machine for testing high molecular polymers There is a certain difference from the usual material tensile performance testing tensile machine, especially the effective stroke of the electronic tensile machine and the sample fixture.
