Heat Deflection Temperature (HDT) Testing Lab
- ASTM D648 / ISO 75 HDT programs
- Method-appropriate flex-bar specimen requirements, support/loading configuration, and conditioning
- Moderate- or higher-load HDT conditions
- Comparative HDT programs
- Engineering test report (PDF) with digital data delivery
- Method-appropriate outputs such as HDT, applied load, heating rate, and test method designation
- Raw data exports available on request, where applicable
- Exact deliverables depend on the selected method condition and specimen configuration
Get Started
Tell us about the material, application, environment, and any method, standard, specimen, or conditioning constraints.
We’ll align the appropriate method, specimen requirements, and deliverables to your objectives, then provide a quote and test plan.
Send the purchase order and arrange delivery of materials or specimens so the program can move into scheduling and execution.
You’ll receive an engineering test report with digital data delivery, along with any agreed raw data or method-appropriate outputs.
FAQs
It depends on the selected standard, material form, and program design. Share what you have and we’ll confirm specimen geometry, minimum specimen count, and any conditioning needs.
Deflection is measured under a specified flexural load while temperature increases at a controlled rate. We can confirm the most appropriate method condition for your program.
We support ASTM D648 and ISO 75 heat deflection temperature testing and can confirm the right path during the initial consult.
Yes—where applicable, programs can be aligned to the required load condition and specimen conditioning requirements before testing begins.
You receive an engineering test report (PDF) and digital data deliverables. Raw data exports are available on request where applicable. Exact outputs depend on the selected method condition and specimen configuration.
Reported outputs depend on the method condition and program setup. Common outputs include HDT, applied load, heating rate, and test method designation.
Typical turnaround for most testing is five business days, but timing can vary based on specimen readiness, conditioning, program setup, and test volume.
Tell us what you need back—HDT values, method condition, raw data, reporting format, and any required standard. We’ll align the program and deliverables before testing begins.
The sections below provide the technical context, standards, specimen considerations, test procedures, and measurement details for this testing service.
Significance & Purpose
The Heat Deflection Temperature (HDT) Technique – also known as the heat distortion temperature technique – measures the temperature at which a plastic material deforms under a specified load. It is a key metric for assessing a material’s ability to retain its mechanical properties under heat and load. HDT is widely used to evaluate the thermal performance and rigidity of thermoplastics and thermosets, making it critical for selecting materials in applications exposed to elevated temperatures and mechanical stress, such as automotive, aerospace, and electrical components.
Standards
To ensure consistency and reliability, HDT testing is governed by well-established standards:
- ASTM D648: Standard Test Method for Deflection Temperature of Plastics Under Flexural Load.
- ISO 75: Plastics — Determination of temperature of deflection under load.
These standards define the test conditions, specimen preparation, and procedures for measuring HDT.
Tests
Tests in the DatapointLabs test catalog that reference heat deflection temperature testing are as follows:
Polymers
| Test | Test Description | Standards |
|---|---|---|
| T-020 | Heat Deflection Temperature | ASTM D648 / ISO 75 |
Principle of Operation
The heat deflection temperature technique involves:
- Specimen Loading: A rectangular specimen is subjected to a specified flexural load (e.g. 0.455 MPa or 1.82 MPa).
- Controlled Heating: The specimen is heated at a constant rate (e.g. 2 °C/min).
- Deformation Monitoring: The temperature is recorded when the specimen deflects to a specified amount (e.g. 0.25 mm for most standards). The HDT represents the temperature at which the material begins to deform significantly under combined thermal and mechanical stress.
Typical Procedure
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Sample Preparation:
- Prepare a rectangular specimen according to the dimensions specified by the relevant standard (e.g. ASTM D648 specifies 127 mm × 13 mm × 3 mm).
- Ensure the specimen is free of defects and properly conditioned, such as drying if necessary.
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Instrument Setup:
- Secure the specimen on the HDT testing apparatus (e.g. ASTM D648 specifies edgewise orientation), where it is supported at two ends and loaded at the center.
- Apply the specified load (e.g. ASTM D648 specifies 0.455 MPa for moderate load, or 1.82 MPa for higher load).
- Immerse and soak the specimen in an oil bath, which ensures uniform heating.
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Heating Program:
- Heat the specimen at a uniform rate of 2 °C/min.
-
Deflection Monitoring:
- Measure the deflection of the specimen using a displacement sensor.
- Record the temperature when the deflection reaches 0.25 mm.
-
Repeat for Multiple Samples:
- Test multiple specimens to ensure reproducibility and reliability of results.
Specimen Types
Specimens used by DatapointLabs in heat deflection temperature testing are as follows:
| Specimen Type | DatapointLabs Test IDs |
|---|---|
| Flex Bars [Details] | T-020 |
Characterization Measurements
The HDT technique provides the following key measurement:
- Heat Deflection Temperature (HDT): The temperature at which the specimen deforms by 0.25 mm under the specified load. This measurement provides insight into a material’s ability to maintain structural integrity under combined thermal and mechanical stress.
Typical Data Reported
- Heat Deflection Temperature: The temperature at which the 0.25 mm deflection occurs.
- Applied Load: The load used during the test, typically either 0.455 MPa or 1.82 MPa.
- Heating Rate: The rate at which the temperature is increased, typically 2 °C/min.
-
Test Method (A or B): Test conditions are often identified by method:
- Method A: Moderate load of 0.455 MPa.
- Method B: Higher load of 1.82 MPa.
Suitable Material Types
The HDT test is specifically designed for rigid and semi-rigid polymers, including:
- Thermoplastics: Such as polyethylene (PE), polypropylene (PP), polycarbonate (PC), polystyrene (PS), and acrylics (PMMA).
- Thermosets: Including epoxy, phenolic, and polyester resins.
- Filled and Reinforced Plastics: Materials with additives like glass fibers or fillers. HDT is less suitable for elastomers or highly flexible materials, which do not show significant difference in deflection at elevated temperatures.
Suitable Applications
The HDT technique is widely applied in industries that require materials to withstand thermal and mechanical stress, including:
- Automotive: Evaluating heat resistance of plastic parts such as bumpers, dashboards, and engine covers.
- Electrical and Electronics: Testing housings, connectors, and insulating materials exposed to heat.
- Construction: Assessing materials used in piping, roofing, and structural components.
- Aerospace: Evaluating lightweight composites for structural applications.
- Consumer Products: Ensuring heat resistance of items like kitchenware and appliances.
- Material Development: Comparing and optimizing new formulations, especially for filled or reinforced plastics.
Conclusion
The heat deflection temperature (HDT) technique provides a critical measure of a plastic material’s resistance to deformation under thermal and mechanical stress. By following ASTM D648 or ISO 75 standards, this test ensures reliable and reproducible results, making it indispensable for material selection, quality control, and performance evaluation in industries such as automotive, construction, aerospace, and electronics.
