Scope:

ASTM D746 test method involves standard impact testing for the brittleness and low-temperature behavior of plastic material and elastomers. The temperature at which half of the test specimens show brittle failure under specified conditions of impact is known as brittleness temperature. ASTM D746 test does not help predict the lowest temperature for the use of a test specimen.

Procedure:

For ASTM D746 test specimen is kept in a specimen holder with a torque wrench at 5 in-lb, then let down into a bath maintained at a specific temperature. An impact of 2000 ± 200 mm/s is applied on the test specimen, followed by examining the specimen for breaking it down into two or more pieces. Any crack visible to the naked eye is also considered a failure. This process is repeated with different samples at low temperatures to generate adequate data to determine brittleness temperature. 

Specimen size:

Brittleness Temperature ASTM D746test usually usesASTM specimens, also known as Type I, with dimensions 6.35 mm × 31.75 mm × 1.91 mm and ISO specimens, also known as Type III, with dimensions 20 mm × 2.5 mm × 2.0 mm. 

Data:

The number of brittleness failures recorded at different test temperatures and final brittleness temperature is reported. 

Conclusion:

ASTM D746 is a standard test method for brittleness temperature of plastics and elastomers by impact.