The heat bending (or heat redirection) temperature (HDT) is an essential property of polymers. It gives a sign at what temperature materials begin to "relax" when presented to a settled load at hoisted temperatures. The HDT is characterized by ASTM D 648 as the temperature at which an example bar of standard measurements diverts by 0.25 mm (0.01 in) less than a focused standard flexural heap of 455 k Pa (66 psi). The example is warmed in a drenching shower at a rate of 2 K/min.

The heat diversion temperature of indistinct materials is identified with the glass progress temperature (formless materials) or softening temperature (crystalline materials). The HDT, is a helpful pointer of as far as possible above which the material can't be utilized for basic applications. Usually investigated the TDS of business evaluations of plastics. In any case, HDT and Tg (or Tm) can't be utilized Interchangeable. The Tg portrays the temperature at which vitrification or glassification starts, for example when "solidifying" of the developments of chain portions (motor units) happens, while the HDT is a plainly visible proportion of the "solidness" of a material when the temperature increments.

The heat diversion temperature or heat contortion temperature (HDT, HDTUL, or DTUL) is the temperature at which a polymer or plastic example twists under a predefined stack. This property of a given plastic material is connected in numerous parts of item configuration, designing and fabricate of items utilizing thermoplastic segments.

For plastic businesses, it is vital to decide the twisting that an item can understanding on utilization of heat. For this reason, heat distortion tester are utilized. This lab testing instrument is structured by the principles set by ASTM D-648 and ASTM D-1525. The hardware gives you the most ideal method for deciding the diversion or disfigurement of the item under a predefined temperature. It is additionally utilized for deciding vicat mellowing temperature of the item. The instrument is furnished with two stations. For manufacture of the inward shower, high review hardened steel is utilized and for creation of external body, Mild steel is utilized and is furnished with a powder covering.