Overview
ISO 11359-3:2019 defines a standardized thermomechanical analysis (TMA) procedure for the determination of the penetration temperature of thermoplastics. The penetration temperature (Tp) is the temperature at which an abrupt displacement of a penetration probe occurs under a defined load as the specimen softens. This method can also be used to evaluate the softening point of thermoplastic materials and is intended for quality control, material comparison and R&D.
Key Topics
- Principle: Measure the onset and rate change of probe penetration while the temperature is increased at a constant rate. The penetration temperature is determined from the intersection of tangents on the TMA curve.
- Apparatus: A TMA instrument compliant with ISO 11359-1 and capable of applying a constant specified force to a penetration probe.
- Penetration probe: Preferably cylindrical with a flat tip. Nominal tip diameters specified are 0.5 ± 0.05 mm or 1.0 ± 0.12 mm, with length not less than 1 mm. Spherical probes are permitted when specimen geometry or aerated foams require them.
- Specimen: Typical thickness between 0.5 mm and 5 mm (thinner specimens down to 0.01 mm can be measured). Recommended specimen dimensions are approximately 5 mm square or 5 mm diameter, with smooth, flat surfaces to ensure full contact.
- Test conditions: Apply a force of 0.50 ± 0.01 N (or another agreed force), maintain for 5–10 minutes before heating, and provide a constant gas flow (dry air, high-purity N2 or inert gas) typically 50–100 ml/min. Heat at a constant rate not exceeding 5 K/min.
- Results: Tp is read from the TMA curve. If multiple stages occur, report Tp for each stage. Report the mean of at least two measurements to the nearest whole degree.
Applications
- Quality control of thermoplastic grades to detect changes in softening behavior.
- Material selection and comparison in product development and failure analysis.
- Research on polymer formulations, additives and processing effects where softening or penetration characteristics are critical.
- Regulatory and certification testing where standardized thermal-mechanical properties are required.
Practical value: The procedure provides a reproducible metric for softening behavior, enabling laboratories to compare materials and verify production consistency using clear instrument setup and reporting rules.
Related Standards
- ISO 11359-1: General principles for thermomechanical analysis (TMA).
- ISO 291: Standard atmospheres for conditioning and testing (referenced for specimen conditioning).
- ISO 472: Plastics - Vocabulary (terms and definitions).
For test reporting, ISO 11359-3:2019 specifies essential items such as sample identification, apparatus model, probe and specimen geometry, conditioning, heating rate, atmosphere, calibration materials, measured Tp (mean value), and any deviations from the standard procedure.
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