Overview - EN ISO 11248:1999 (ISO 11248:1993)
EN ISO 11248:1999, published as ISO 11248:1993, specifies a standardized method to evaluate the short-term performance of thermosetting moulding materials at elevated temperatures. The standard defines how to measure mechanical, electrical, thermal and other relevant properties under defined high-temperature conditions and to derive the Relative Performance Temperature (RPT) - a practical index for short-term elevated-temperature behaviour. When combined with long‑term property data, the RPT helps designers and engineers predict material performance in real-world thermal environments.
Key topics and technical requirements
- Scope: Test method for thermosetting moulding materials to determine short-term performance at elevated temperatures and to calculate the RPT.
- Test preparation
- Specimen manufacture per relevant standards (ISO 295, ISO 10724) and post-curing per manufacturer recommendation.
- Conditioning: 24 hours in atmosphere 23/50 (ISO 291).
- Apparatus
- Forced-draught oven with controlled airflow (tubular oven if contamination must be avoided).
- Property-specific test equipment complying with ISO 178, ISO 527-1, ISO 604 or other applicable standards.
- Test procedure
- Establish reference (ambient) property values under atmosphere 23/50.
- Determine an initial test temperature from DMA (glass transition, Tg) or DTUL; round down to the nearest 25 °C multiple.
- Expose specimens 24 h at each test temperature, test after 15 min in fixture.
- Adjust temperature in 25 °C increments until at least four data points are obtained (1–2 below 50% of reference).
- Use linear regression to find the temperature where the property equals 50% of the reference value - this is the RPT.
- Reporting: Must include material identification, moulding parameters, test temperatures and oven type, reference values, RPT (with data plot), post‑cure details, specimen sizes/numbers and visual observations.
Applications and who uses this standard
- Materials engineers and product designers assessing thermosetting compounds for:
- Electrical insulation and connector components
- Automotive and aerospace structural or electrical parts
- Consumer electronics and high‑temperature housings
- Test laboratories and quality control teams performing comparative short‑term thermal evaluations
- OEMs specifying material selection criteria and safety margins for elevated-temperature service
Related standards
- ISO 178 (flexural properties), ISO 527‑1 (tensile properties), ISO 604 (compressive properties)
- ISO 295, ISO 10724 (specimen moulding)
- ISO 291 (conditioning atmospheres), IEC 216‑2 (thermal endurance guidance)
- ISO 2578 (long‑term time‑temperature limits) - for complementary long‑term assessment
Keywords: EN ISO 11248:1999, ISO 11248:1993, thermosetting moulding materials, short-term performance, elevated temperatures, relative performance temperature, RPT, mechanical properties, electrical properties, thermal testing.