---
title: How HDT and VICAT Tests Work for Thermoplastic Materials
description: The HDT and VICAT tests determine the temperature sensitivity of a plastic sample subjected to bending or penetration, let's see how they work.
---

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# [How HDT and VICAT Tests Work for Thermoplastic Materials](https://www.weerg.com/guides/hdt-vicat-temperature-test)

 Written by [Fabio Trotti](https://www.weerg.com/guides/author/fabio-trotti) | Feb 22, 2022

The need for **reliable data from repeatable tests** that can be used by designers for material selection is the main reason why **a number of standardized tests have been developed over time to characterise materials**.

## What are temperature tests?

One such type of test is **temperature testing**. They are particularly important for understanding and **describing the thermal behaviour of polymers**, the properties of which can vary markedly with temperature. In these tests, **the deformation and softening temperatures** of polymeric materials are verified and quantified.

## Vicat method

The sample of material to be tested is fixed in the lower part of the instrument where it is immersed in a heated bath. During the test, the temperature of the bath is increased in a controlled manner by a uniform ramp, while an indenter with an area of 1mm2 and a constant load towards the material is placed on the upper surface of the sample.

The indenter will sink into the material and when it reaches a depth of 1 mm, it will correspond to the temperature of the Vicat point of the material under test.

  

In the image it is possible to see a scheme of the test apparatus with the number 3 highlighting the punch that applies the load to the component, while on the right you can see a test machine with 6 independent stations. **The reference standard for this test is ISO 306**.

## HDT Method

**HDT method shows some similarities to the Vicat method** as the specimen is placed in a thermostatic bath in this test as well. **What changes, however, is the type of specimen**, which is usually a prismatic rod, and the manner in which the component is stressed, as it is tested in flexion, with a constant applied force. **The HDT temperature is reached when the deformation of the specimen exceeds 0.2% deflection.**

In the picture we can see a specimen during the test (left) and at the end of the test (right) after a deformation of 0.25 mm. There are 3 different tests called A - B - C according to the loads to which the sample is subjected, respectively 1.8 MPa - 0.8 MPa - 8 MPa. The reference standard for this test is ISO 75. This test provides us with important information to identify the usable temperatures for a given material and also allows us to compare different materials in a direct and repeatable way.

 

**The behaviour of a given material at different temperatures is extremely important for determining how to realise a design**. That is why **in Weerg**, by testing all our materials, **we have unique data which represents a performance benchmark between different materials.** [You can view the comparative material tables here](https://www.weerg.com/hubfs/Datasheets/Weerg%20Materials%20Datasheet%20rev4.0-ENG.pdf).

 

**If you still have doubts, questions or need additional information, our experts are available to support you in your choice**: [contact them here](https://www.weerg.com/contact-us) to discuss your project and your doubts about the material.

[View full post](https://www.weerg.com/guides/hdt-vicat-temperature-test)

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