SIST EN ISO 75-1:2020 PDF

Overview

EN ISO 75-1:2020 - Plastics: Determination of temperature of deflection under load (general test method) defines a standardized laboratory procedure to measure the temperature at which a plastic specimen deflects under a specified flexural load. Commonly referred to as the heat deflection temperature (HDT) or heat distortion temperature, this method uses three-point bending of defined test specimens while the temperature is raised at a controlled rate to determine the temperature of deflection under load.

Key topics and technical requirements

• Test principle: Three‑point bending under a constant load produces a defined flexural stress; the temperature at which the specimen reaches the specified deflection (flexural strain increase) is recorded.
• Specimen types and dimensions: Preferred specimen shapes and dimensions are specified to ensure comparable results for different materials.
• Loads and flexural stress: Different constant loads and stress conditions are defined to suit material classes.
• Heating and measurement: A controlled, uniform temperature increase is required; accurate temperature measurement (thermocouples or resistance thermometers) and deflection measurement are specified.
• Conditioning: Specimens shall be conditioned in standard atmospheres (see ISO 291) before testing.
• Data interpretation limits: Results assess relative behavior at elevated temperature under a specified heating rate. The standard explicitly states data are not intended for design analysis or to predict end‑use endurance, and test conditions may not represent actual service conditions.
• Comparability: True comparability of HDT data is best achieved between materials with similar room‑temperature flexural modulus.

Practical applications

• Material selection and comparison: Use HDT values to compare thermal stiffness among polymers, filled plastics and reinforced materials (short-fibre vs long-fibre types addressed in ISO 75-2 and ISO 75-3).
• Quality control: Routine production testing to monitor batch-to-batch consistency in thermal performance.
• R&D and formulation: Evaluate the effect of additives, fillers or processing on elevated‑temperature rigidity.
• Regulatory and standards compliance: Provide standardized thermal property data for datasheets and specifications.

Who uses this standard

• Materials laboratories and third‑party testing bodies
• Polymer manufacturers, compounders and processors
• Design and application engineers selecting materials for elevated‑temperature service
• OEMs and quality assurance teams

Related standards

• ISO 75-2 - specific requirements for most plastics and ebonite (short fibres ≤ 7.5 mm)
• ISO 75-3 - specific requirements for high‑strength thermosetting laminates and long‑fibre reinforced plastics (> 7.5 mm)
• ISO 291 (conditioning), ISO 16012 (specimen dimensions), IEC 60584-1 / IEC 60751 (temperature sensors)

Keywords: EN ISO 75-1:2020, heat deflection temperature, HDT, temperature of deflection under load, plastics testing, three-point bending, flexural stress, test specimen.