Heat Deflection Temperature (HDT) Testing Services

HDT testing measures the heat resistance of materials. It determines the temperature at which a standard test bar deflects under a load. Two common methods are Honda HES D 2500 and ISO 75-3, along with ISO 75-2 and ASTM D 648 Method A and B. These methods have distinct benefits and drawbacks and should be specifically chosen based on the application.

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Heat Deflection Temperature (HDT) Testing Services

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Overview
Scope, Applications, and Benefits
Test Process
Specifications
Instrumentation
Results and Deliverables

Overview

Heat Deflection Temperature (HDT) tests, described in ASTM D648 and ISO 75, measure the temperature at which a plastic material deflects under a specified load. This tests the ability of plastic materials to maintain their structural integrity at a particular temperature.

HDT tests are used to assess the thermal resistance of thermoplastics and thermosets. This is particularly important to plastic manufacturers who need to know the temperature limits of plastic components used in industries such as cars, electronics, and construction.

Scope, Applications, and Benefits

Scope

HDT testing evaluates the temperature at which plastic materials begin to deform under a specified load. The test is performed by heating a specimen at a controlled rate while applying a constant bending stress until a defined deflection occurs.

The scope includes:

Determination of heat deflection temperature of plastics
Evaluation of thermal resistance under load
Testing of thermoplastics and thermoset materials
Material comparison for thermal performance
Quality control and product design validation

Applications

Automotive plastic components
Electrical and electronic housings
Structural plastic parts
Consumer product components
Engineering polymer materials

Benefits

Determines temperature resistance of plastics
Helps select materials for high-temperature applications
Supports product design and engineering decisions
Enables material comparison and quality control
Improves product reliability and performance

Test Process

Specimen Preparation

Test specimens are molded or machined to standard dimensions and conditioned before testing.

Load Application

The specimen is placed in the testing apparatus and subjected to a specified bending load.

Controlled Heating

The specimen is heated at a constant rate in a temperature-controlled oil or air bath.

Deflection Measurement

The temperature at which the specimen reaches the specified deflection is recorded as the HDT value.

Technical Specifications

Parameter	Details
Test Type	Thermal deformation under load
Applicable Materials	Thermoplastics and thermosets
Specimen Orientation	Flat rectangular specimen
Heating Rate	Typically 2 °C/min
Applied Stress Levels	0.45 MPa or 1.8 MPa
Deflection Limit	0.25 mm
Test Medium	Oil bath or air heating system
Measured Parameter	Heat Deflection Temperature (°C)

Instrumentation Used for Testing

Heat Deflection Temperature Tester
Temperature Controlled Oil Bath / Heating Chamber
Load Application System
Deflection Measurement Gauge
Temperature Sensors / Thermocouples

Results and Deliverables

Heat Deflection Temperature (HDT) value in °C
Applied stress level used during testing
Deflection measurement data
Test conditions and parameters
Detailed laboratory test report

Infinita Lab: Your Material Testing Partner

Contact Infinita lab for Heat Deflection Temperature (HDT) Testing by major benefits like:

End-to-end testing management, faster turnaround, reduced administrative burden.

Confidence in accurate results and reduced stress in vendor coordination.

Enhanced reputation for product reliability and innovation.

Engineers and R&D managers focus on core work rather than testing logistics.

Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you. Request a Quote

Frequently Asked Questions

Heat Deflection Temperature testing determines the temperature at which a plastic material deforms under a specified load, indicating its ability to maintain structural rigidity when exposed to elevated temperatures.

HDT testing helps evaluate the thermal performance of plastics, ensuring materials maintain mechanical stability and dimensional integrity when used in applications exposed to high operating temperatures.

HDT testing is typically performed on thermoplastics, thermosetting plastics, and reinforced polymer composites used in automotive, electronics, construction, and industrial components.

A specimen is subjected to a constant bending load while the temperature of the surrounding medium is gradually increased until a specified deflection occurs, indicating the heat deflection temperature.

The test result is reported as the temperature at which the specimen reaches a defined deflection under load, reflecting the material’s heat resistance and structural stability under thermal stress.