Test speciment ASTM D638 - Thermoplastic polymers, elastomers and additives

Tension tests for plastic materials for extrusion and molding according to ISO 527-2, based on the general principles provided in ISO 527-1. Forms and dimensions of the specimen:

In order to perform these stress tests, the test specimens are placed in an "appropriate manner" in the jaws of a "dynamometer" test machine and are subjected to a controlled tension and speed until they fail.The test speeds vary according to the type sample to achieve a degree of deformation of 1% / min and an extensometer is used to measure the measurement parameters.The data resulting from the stress test is used to inform the properties of the material, such as stress, deformation, modulus of Stress and elongation ISO 527 is very similar to ASTM D638 with the fundamental exception of the analysis of the non-linear portion of the stress-strain curve of the material.

Stress deformation curves for plastic materials generally contain a linear elastic region, as well as a non-linear plastic region. The module needs to be measured within the linear elastic portion, where there is very little deformation.

Both ISO 527-1 / -2 and ASTM D 638 specify methods for tensile testing. For most materials, the test results according to the two standards will be similar. But for plastics that have little or no linear region, the variation between ASTM and ISO can be important. Given the vicoelastic nature of plastics, these tests can be performed with temperature chambers to better simulate the final environments. Finally, the geometries of the specimens, test speeds and the way to find the results differ from each other.