Heat deflection/distortion temperature

“Heat deflection temperature” can be defined as the temperature at which a standard test sample deforms (bends) under a predefined load.

Testing procedure

A test sample of 80x10x4 mm is introduced in the test apparatus.

In function of the chosen method, the sample is subjected to a load of 0,45; 1,8 of 8 MPa. This is then placed in an oil bath that is heated at constant rate (120°C/h), until a certain deflection occurs. (the deflection depends on the material/dimension)

Testing applications

  • Determination of the resistance to deformation at certain temperatures
  • Comparison of the resistance to temperature of different materials


ISO 75-2:2013 -- Plastics -- Determination of temperature of deflection under load


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