Overview
ISO 11248:1993 - Plastics - Thermosetting moulding materials - Evaluation of short‑term performance at elevated temperatures - specifies a laboratory method to determine mechanical, electrical, thermal and other properties of thermosetting moulding materials when tested under defined elevated‑temperature conditions. The standard defines how to derive the Relative Performance Temperature (RPT) - the temperature at which a chosen property falls to 50% of its reference value - to complement long‑term property data and help engineers predict short‑term high‑temperature behaviour.
Key topics and requirements
- Scope: Short‑term testing under defined elevated temperatures for thermosetting moulding materials to obtain RPT values.
- Specimen preparation: Mould specimens in accordance with ISO 295 and ISO 10724; annealing if required per manufacturer recommendations.
- Conditioning: Condition specimens 24 h in atmosphere 23/50 (ISO 291) before testing.
- Initial test temperature: Select from DMA (glass transition Tg from tan δ peak) or DTUL (deflection temperature under load) if DMA unavailable. Initial temperature is the next lower multiple of 25 °C.
- Test procedure:
- Test properties specified in ISO 178, ISO 527‑1, ISO 604 or other appropriate standards (flexural, tensile, compressive, dielectric strength, etc.).
- Use a temperature‑controlled oven (preferably forced‑air circulation) and test apparatus with its own temperature control so test temperature matches oven.
- Condition specimens at the chosen test temperature for 15 minutes on the test support before measurement.
- Start at the initial temperature and move in 25 °C increments, testing successive specimen sets until at least four data points are obtained with between one and two points below 50% of the reference property.
- Data analysis: Use appropriate data transformations and a linear regression model to determine the temperature where the property equals 50% of the reference; this temperature is the RPT.
- Reporting: Test report must include material type/grade, moulding and processing details, moulding date, oven type/temperatures, anneal (if any), properties measured, specimen dimensions and counts, reference values and RPT(s), and observations (shrinkage, cracking, discoloration). Include the data‑point plot used to determine RPT.
Applications and users
- Material suppliers, R&D labs and test houses validating thermosetting resin performance.
- Design engineers and specifiers selecting materials for short‑term elevated‑temperature service (mechanical loading, electrical insulation, thermal stability).
- Quality and compliance teams assessing batch conformance or comparing formulations.
- Useful in industries such as automotive, electrical/electronic insulation, industrial appliances and any application where thermosetting plastics experience short‑term heat exposure.
Related standards
- ISO 178, ISO 527‑1, ISO 604 (mechanical property test methods)
- ISO 291 (conditioning atmosphere 23/50)
- ISO 295, ISO 10724 (specimen moulding)
- IEC 216‑2 (guidance on thermal endurance test criteria)
- References to DMA (dynamic mechanical analysis) and DTUL for initial temperature selection
Keywords: ISO 11248:1993, thermosetting moulding materials, short‑term elevated temperature testing, Relative Performance Temperature, RPT, DTUL, DMA, thermosetting plastics, high‑temperature performance.
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