Deflection Temperature Under Load (DTUL) - ASTM D648
The temperature at which a test specimen deflects 0.25 mm when loaded in 3-point bending at a specified maximum outer fiber stress. Deflection temperature is used to determine short-term heat resistance.
A test specimen is loaded in 3-point bending in the edgewise direction. Outer fiber stresses used for testing are 0.455 MPa (66 psi) and 1.82 MPa (264 psi). The temperature is increased at 2°C/min until the specimen deflects 0.25 mm (0.010 in).