Introduction to ISO 75
ISO 75 is a standardized test method designed to determine the temperature of deflection under load (flexural stress under three-point loading) for various materials, including plastics. This property is crucial in understanding how a material behaves under specific loads and elevated temperatures, ensuring its suitability for various applications in industries such as automotive, aerospace, and electronics. ISO 75 test method was introduced in three parts: such as General Test Method; Plastics and Ebonite Testing (ISO 75-2); High-Strength Thermosetting laminates and long fibre-reinforced plastics testing (ISO 75-3).
ISO 75 test method is useful for qualitative characterization, research, durability evaluation, and specification purposes.
ISO 75 Test Method
ISO 75 test method is performed using a three-point bending configuration. The testing apparatus includes a controlled temperature chamber or oven capable of accurately increasing the temperature. The test proceeds as follows:
| Preconditioning and Loading | The specimens are subjected to a pre-determined conditioning period at a specified temperature. The specimens are then placed in the testing apparatus and subjected to a defined load. Simultaneously, the temperature is gradually increased at a specified rate. |
| Deflection and Temperature Recording | The deflection of the specimen is continuously monitored during the temperature increase until a predetermined deflection threshold is reached. At this point, the temperature of deflection under load is recorded. |
ISO 75 Specimens
| Specimen Details | The preferred dimensions for the test specimens are specified by different methods described in ISO 75. ISO 75 test specimens are typically in the form of rectangular bars or discs. |
| Specimen dimensions | The dimensions of the specimens are specified in the standard, taking into account the material type and intended application |
| Specimen preparation | The specimens are prepared by machining, molding, or fabrication methods specific to the material being tested. |
ISO 75 Results
The test method ISO 75 provides crucial information about a material’s dimensional stability and load-bearing capabilities at elevated temperatures. The temperature of deflection under load serves as an indicator of the material’s thermal and mechanical performance, enabling engineers and manufacturers to make informed decisions regarding material selection for specific applications.
Tests Related to ISO 75
ASTM D648 standard provides a similar test method for determining the heat deflection temperature of plastics.
