ASTM D 8540 : 2023

1.1This test method covers the determination of the temperature at which an arbitrary deformation occurs when specimens are subjected to an arbitrary set of testing conditions.

1.2This test method applies to molded and sheet materials available in thicknesses of 3 mm (¹/₈in.) or greater and which are rigid or semirigid at normal temperature.

1.3The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.

1.4This standard and ASTM D648 address the same subject matter and are essentially the same test. However, due to known differences in results caused by the differences in heat transfer media, the results from this standard and ASTM D648 must not be compared or considered equivalent.

1.5This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.6This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.