Overview
ISO 11359-2:2021 specifies a thermomechanical analysis (TMA) test method for plastics using thermodilatometry to determine the coefficient of linear thermal expansion (CLTE) and the glass transition temperature (Tg). This part of the ISO 11359 series applies specifically to TMA apparatus and describes specimen preparation, apparatus requirements, test procedure, calculation methods and reporting. The standard replaces and updates the 1999 edition with revised test-load, purge-gas conditions and clearer reference-specimen evaluation.
Keywords: ISO 11359-2:2021, thermomechanical analysis, TMA, coefficient of linear thermal expansion, glass transition temperature, thermodilatometry, plastics testing.
Key Topics and Requirements
- Scope & principle
- Measurement of dimensional change of solid plastic specimens as a function of temperature using TMA to derive CLTE and Tg.
- Apparatus
- Equipment compliant with ISO 11359-1; capable of compression and/or tension modes and controlled atmosphere (dry air or inert gas preferred).
- Specimens
- Standard rectangular specimens typically 5–10 mm long and ~5 mm wide; ends parallel; at least three specimens per sample.
- Orientation (machine/transverse) must be recorded when relevant.
- Test conditions
- Probe load sufficient for reliable contact but low enough to avoid specimen compression (preferably 1 mN to 50 mN).
- Gas flow around specimen typically 0–100 ml/min (dry inert gas or dry air recommended).
- Heating rate not more than 5 K/min.
- Preconditioning (to remove thermal memory) may include heating 50 °C below to 50 °C above Tg and holding.
- Calculation & results
- Differential CLTE (α) from local slope dL/dT of the TMA curve.
- Mean CLTE over a temperature interval ΔT calculated by Method A (direct from TMA) or Method B (with reference specimen).
- Tg determination by TMA curve analysis; CLTE reported before and after Tg as applicable.
- Calibration & reporting
- Apparatus calibration per ISO 11359-1; detailed test report requirements defined.
Applications and Who Uses It
- Materials scientists & polymer engineers - characterize thermal expansion and glass transition for research and development.
- Quality control & test laboratories - verify dimensional stability and batch consistency of plastic products.
- Design and product engineers - inform tolerancing, thermal cycling performance and multi-material assembly (e.g., polymer-to-metal joints).
- Failure analysis & certification bodies - investigate thermal distortion and compliance with specifications.
- Instrument manufacturers - ensure TMA systems meet procedural requirements.
Practical use cases include material selection for temperature-sensitive components, predicting shrinkage/warpage, thermal compatibility checks in assemblies, and validating formulations or processing changes.
Related Standards
- ISO 11359-1 - Thermomechanical analysis (TMA) - General principles (calibration, terminology).
- ISO 291 - Standard atmospheres for conditioning and testing.
- ISO 472 - Plastics - Vocabulary.
This summary helps engineers and lab managers quickly understand the scope, key technical requirements and practical value of ISO 11359-2:2021 for TMA-based thermal characterization of plastics.
Open preview (PDF)Plastics — Thermomechanical analysis (TMA) — Part 2: Determination of coefficient of linear thermal expansion and glass transition temperature