Heat Deflection Temperature (HDT) Testing

Heat Deflection Temperature (HDT) Testing of Plastics

A measure of the resistance of a polymer to change under a given load at an elevated temperature; It is called the Heat Deflection Temperature (HDT). Also called Heat Deflection Temperature, Deflection Temperature Under Load (DTUL), or Heat Deflection Temperature Under Load (HDTUL), the main purpose of the test is to test the hardness of a material as temperature increases.

The Heat Deflection Temperature Test (HDT) determines the temperature at which a polymer test bar will bend 0.25 mm under a certain weight. For plastics that are easily affected by heat, the reaction of the product should be known during the design and R&D studies. For this reason, Heat Deflection Temperature (HDT) Test is performed before production.

The reasons for performing the Heat Deflection Temperature (HDT) Test can be listed as follows:

Comparing two different materials
In the product design and production stages of products using thermoplastic components
In processes such as injection molding, if the Heat Deflection Temperature (HDT) value is high, the molding process will be shortened.

ASTM D 648: Standard Test Method for Deflection Temperature of Plastics Under Edge Bending Load

ISO 75-1:Plastics - Determination of deflection temperature under load - Part 1: General test method

ISO 75-2:Plastics - Determination of deflection temperature under load - Part 2: Plastics and ebonite

ISO 75-3:Plastics - Determination of deflection temperature under load - Part 3: High strength thermosetting laminates and long fiber reinforced plastics