Scope:

ASTM D3769 is used for determining the heat sag of microcellular urethane. This method is essential for deformation in the baking assembly process and paint applications. It provides practical methods to determine the potential tendency of microcellular materials to deform.

Procedure:

In ASTM D3769, the thickness is measured in the clamping area of the test specimen. The specimen is clamped in the fixture with a 100±1 mm unsupported overhang; the distance is determined between the base and the unsupported end. The clamped specimen is placed in the oven to heat for one minute. Measurement is repeated after 5 minutes.

Specimen size:

For ASTM D3769, the specimen length should be 125 mm, 25±1 mm in width, and the temperature of the oven must be 120±1°C.

Data:

The following equation is used in ASTM D3769 for the calculation of microcellular urethane’s high-temperature sag.

Sag = Ao – Af

Conclusion:

ASTM D3769 is used for determining the heat sag of microcellular urethane.