Heat distortion temperature

This material test assesses the dimensional stability of plastics as a function of temperature.

It determines the temperature at which a specified deflection occurs in a specimen positioned on bearings at either end under a defined, concentric load when the temperature is increased at a uniform rate. This value, referred to as the outer fibre strain, is 0.2 % .

The standard makes a distinction between three different methods:

HDT, Method A: flexural stress s = 1,8 N/mm² = const.
HDT, Method B: flexural stress s = 0,45 N/mm² = const.
HDT, Method C: flexural stress s = 8,0 N/mm² = const.