ASTM D648
Standard Test Method for Deflection Temperature of Plastics Under Flexural Load in the Edgewise Position.

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

Test Procedure:
The bars are placed under the deflection measuring device. A load of 0.45 MPa or 1.80 MPa is placed on each specimen. The specimens are then lowered into a silicone oil bath where the temperature is raised at 2° C per minute until they deflect 0.25 mm for ASTM, 0.32 mm for ISO flatwise, and 0.34 mm for ISO edgewise.

Specimen size:
ASTM uses a standard bar 5" x ½" x ¼". ISO edgewise testing uses a bar 120mm x 10mm x 4mm. ISO flatwise testing uses a bar 80mm x 10mm x 4mm.

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