Heat Deflection Temperature

The Heat Deflection Temperature is the temperature at which an elastomeric material can be deformed under a specific load.  This is an important parameter which is useful in the design and manufacture of plastic components. 

The Heat Distortion Temperature for a material can be determined experimentally.

ASTM D8 defines the Heat Distortion Temperature as the temperature at which a bar of standard dimension experiences a deflection of .25mm when loaded with a flexural load of  455 kPa.  The heating is done at the rate of 2K per minute. 

A material cannot be used for structural applications at a temperature above its Heat Distortion Temperature. 

In Injection moulding, the part which is moulded can be removed from the mould once it is near or below the Heat Distortion Temperature.