ASTM D3768 Microcellular Urethanes Flexural Recovery

Scope:

At room temperature, ASTM D3768 test method is used to determine a material’s capacity to recover after a 180° bend around a 12.7-mm (0.5-in.) diameter mandrel. Any specifications for the material being tested must be consulted before beginning with this test technique.

Procedure:

Any test specimen preparation, conditioning, dimensions, or a combination, and testing parameters described in the material specification supersedes those mentioned in the ASTM D3768 test methods. If no material specifications are provided, the default conditions apply.

In ASTM D3768, the thickness of the specimen is measured to the closest 0.03 mm. The test specimen is placed in the specimen’s lower slot. The specimen’s end flush is clamped and put with the back of the bent mandrel’s face. Initial reading is taken where the test specimen’s mandrel edge (the surface in contact with the bending mandrel) intersects the protractor scale. 30 mm (1.25 in.) of force is applied from the clamped and bent specimen 180 degrees around the mandrel. The specimen is held in a bent position for 5 seconds before releasing it. The intercept of the specimen’s mandrel edge is measured on the protractor scale. The flexural recovery value is the difference between these readings and the initial reading.

Specimen size:

For ASTM D3768 testing, the specimen should be 4mm thick with a width of 25 mm and 150 mm.

Data:

Flexural Set (30 s) = φ30 s − φ0

Flexural Set (300 s) = φ300 s − φ0

Conclusion:

At room temperature, ASTM D3768 test method is used to determine a material’s capacity to recover after a 180° bend around a 12.7-mm (0.5-in.) diameter mandrel.