4.1 Because of the wide variety of potential uses of rigid cellular plastics, artificial exposure to estimate the effective behavior of these materials must be based, to a great extent, on the intended application. Toward this end, this test method is intended to recommend a variety of conditions from which one or more of the desired exposure conditions can be selected. (Note 3)

4.2 The conditions recommended in this test method have been widely used in artificially exposing rigid cellular plastics and in determining the effects of various temperatures and humidities on these materials. Final test measurements are determined after the specimens return to room temperature. Where specified, the specimens will be tested at the exposure condition, but must be reported as such.

4.3 Dimensional changes measured by this test method can be used to compare the performance of materials in a particular environment, to assess the relative stability of two or more cellular plastics, or to specify an acceptance criterion for a particular material. The results of this test method are not suitable for predicting end-use product performance or characteristics, nor are they adequate for engineering or design calculations.

Note 3: Where thermal shock is known or suspected to occur due to rapid heating to (or cooling from) a particular temperature, guidance on the permissible heating or cooling rates, or both, shall be obtained from the manufacturer of the material concerned.

Note 4: The dimensional change of a specimen can vary depending upon the age of the sample or the length of time between specimen preparation and the beginning of the test, or both.

4.4 Before proceeding with this test method, reference shall be made to the specification of the material being tested. Any test specimen preparation, conditioning, dimensions, or testing parameters covered in the materials specification, or combination thereof, shall take precedence over those mentioned in this test method. If there are no specifications, then the default conditions apply.

1.1 This test method covers procedures for the thermal and humid exposure of rigid cellular plastics. Conditions used shall be agreed upon between the purchaser and the supplier.

Note 1: A list of commonly used exposure conditions is found in Table 1.

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

1.3 This 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.

Note 2: This test method is equivalent to ISO 2796 in the sampling and calculation sections. It is not equivalent to ISO 2796 in the procedure section.

1.4 This 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.