This test method is particularly applicable to nonrigid thermoplastic sheeting or film made by the calender or extrusion process. The test gives an indication of lot-to-lot uniformity as regards to the degree of internal strains introduced during processing.
The heating medium in this test method is air and may not yield the same results as Test Method D 2732, which uses a liquid medium.
Before proceeding with this test method, reference should be made to the specification of the material being tested. Any test specimen preparation, conditioning, dimensions, or testing parameters, or combination thereof, covered in the relevant ASTM material specification shall take precedence over those mentioned in this test method. If there are no relevant ASTM material specifications, then the default conditions apply. Table 1 of Classification System D 4000 lists the ASTM material standards that currently exist.