Determine the maximum temperature your plastic can withstand under load. Critical for parts that must maintain dimensional stability in elevated temperature applications.
Heat Deflection Temperature (HDT), also known as Heat Distortion Temperature, is the temperature at which a polymer sample deforms a specified amount under a defined load. This standardized test (ASTM D648 / ISO 75) is one of the most important specifications for thermoplastics used in structural or load-bearing applications.
HDT provides a practical measure of a material's short-term heat resistance under load. Unlike melting point or glass transition temperature, HDT simulates real-world conditions where parts must support weight or resist deformation while exposed to elevated temperatures.
Important Note: HDT is not the same as continuous use temperature or long-term heat aging resistance. It's a short-term deflection test that helps rank materials and predict performance in specific loading scenarios.
Tested at two common stress levels: 0.45 MPa (66 psi) and 1.82 MPa (264 psi), allowing comparison across materials and applications.
Helps determine if a material can handle your application's temperature requirements while maintaining dimensional stability.
Enables quick comparison between different grades, formulations, and competing materials for material selection.
Verify that incoming materials meet HDT specifications and detect batch-to-batch variations in heat resistance.
HDT tells you the maximum temperature at which your part will maintain its shape under a specified load. This is critical for:
HDT allows you to compare materials on an apples-to-apples basis:
When designing a new product, HDT is often the first thermal property engineers check. If your part needs to function at 120°C, you need a material with an HDT significantly higher than that. HDT testing helps you quickly eliminate unsuitable materials and focus on viable candidates.
Developing heat-resistant formulations? HDT testing shows how glass fiber content, mineral fillers, heat stabilizers, and other additives impact high-temperature performance. Optimize your formulation to achieve target HDT values while balancing cost and processability.
Many applications require materials to meet minimum HDT specifications. Regular HDT testing ensures your incoming materials meet these requirements and that your manufacturing process doesn't degrade thermal performance. Catch problems before parts fail in the field.
Wondering how your material stacks up against the competition? HDT testing of competitor parts reveals their heat resistance and helps you understand if you need to reformulate to remain competitive.
When parts warp, sag, or deform in service, HDT testing can reveal if the root cause is insufficient heat resistance. Compare the HDT of failed parts to good parts and to the original material specification to identify the problem.
HDT is typically measured at two different stress levels, each providing different insights:
The lower stress condition, used for applications with minimal load or stress. Provides a higher temperature value and is often cited in material datasheets as the primary HDT specification.
The higher stress condition, more representative of load-bearing applications. Results in lower temperature values but better predicts real-world performance under stress.
We follow standardized testing protocols ensuring your results are accurate, repeatable, and comparable to industry data.
We don't just report numbers—we explain what your HDT values mean for your specific application and recommend solutions if improvements are needed.
We combine HDT with DSC, TGA, and mechanical testing to provide complete thermal and mechanical characterization of your materials.
Quick testing and reporting so you can make timely decisions about material selection, formulation changes, or quality issues.
Get precise HDT testing with expert guidance on material performance. Contact our lab today.
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