ISO 9924-3:2024

Overview - ISO 9924-3:2024 (Thermogravimetry for rubber composition)

ISO 9924-3:2024 specifies a thermogravimetric analysis (TGA) method to determine the main constituents of rubber compounds - notably elastomer(s), carbon black and mineral fillers - for vulcanizates and uncured compounds. The method produces a characteristic thermogram or “fingerprint” of the tested material. It applies to a wide range of rubbers including hydrocarbon rubbers (NR, BR, SBR, EPDM, etc.), halogenated and nitrogen-containing rubbers (CR, FKM, NBR, HNBR, etc.), and polysiloxane rubbers (VMQ). The standard covers raw and compounded materials, vulcanized and unvulcanized, with or without prior extraction.

Key technical topics and requirements

• Principle: Controlled heating of a weighed test portion under an inert atmosphere (nitrogen) followed by oxidation (air or oxygen) to record mass loss vs temperature/time (TGA curve) and its derivative (dw/dT).
• Reagents & gases: High-purity nitrogen (≥ 99.995% mass fraction, O2 < 10 mg/kg) and dry air (or reconstituted N2/O2 ≥ 99.5%).
• Apparatus: Thermogravimetric analyser (microbalance readable to 1 μg), controlled oven to ≈1000 °C, gas selector, gas flow measurement (recommended ~100 cm3/min), and data acquisition.
• Sample preparation: Test portion typically 8 mg ± 3 mg; conditioning per ISO 23529; optional solvent extraction (ISO 1407) to remove plasticizers before TGA.
• Procedures A & B: Two operating programmes defined - Procedure A for carbon-containing rubbers (target N2 temp 600 °C) and Procedure B for polysiloxane/fluorocarbon rubbers (target N2 temp 800 °C). Heating rates, switching temperature (400 °C), and final oxidation steps are specified in Table 1.
• Data analysis: Use mass change curve and derivative plot to identify key mass points (m0 initial, m1 after pyrolysis, m2 after carbon black combustion, m3 residue) and compute mass fractions. Note that some rubbers (halogenated, nitrogenous) may leave carbonaceous residues that can interfere; the standard prescribes mitigation and interpretation guidance.
• Reporting & precision: Requirements for recordings, interpretation, corrections for extractables, and test report content are specified. Annexes include recommended procedures, thermogram examples, and precision data.

Practical applications - who uses ISO 9924-3:2024

• Quality control and incoming inspection in rubber manufacturing and compounding plants.
• Material characterization in R&D laboratories developing new elastomers, fillers or formulations.
• Failure analysis and root-cause investigations where composition fingerprints help identify contamination or formulation shifts.
• Independent testing laboratories and OEMs requiring standardized compositional analysis of vulcanizates and uncured compounds.
• Regulatory and specification compliance where verified material composition or batch comparability is needed.

Related standards and references

• Other parts of the ISO 9924 series (list on ISO website) for complementary TGA methods.
• ISO 23529 (conditioning of samples) and ISO 1407 (extraction of plasticizers/additives) are referenced for sample preparation and extraction procedures.

Safety note: Users should follow normal laboratory safety and environmental-disposal practices as some procedures generate hazardous decomposition products.