Overview
ISO 7270-2:2024 - Rubber - Analysis by pyrolytic gas-chromatographic methods - Part 2: Determination of styrene/butadiene/isoprene ratio specifies a standardized pyrolytic gas‑chromatography (py‑GC) method to determine the styrene/butadiene/isoprene ratio in copolymers, terpolymers or blends of these polymers. The method applies to raw rubbers and to unvulcanized or vulcanized compounds. Results are obtained by pyrolysing small, extracted test samples and analysing volatile pyrolysis products (styrene, butadiene, isoprene) by gas chromatography against calibration curves.
Key topics and technical requirements
- Scope: Applicable to copolymers/terpolymers and blends consisting of styrene, butadiene and isoprene; results can be affected by resins or high sulfur content.
- Sample preparation: Process and extender oils and additives must be removed (extraction) following ISO 1407:2023, method B; samples dried before analysis.
- Calibration: Minimum of three calibration samples (including one close to expected composition) are required to build calibration curves used to quantify the three monomers.
- Pyrolyser types: Micro‑furnace, Curie‑point or platinum‑filament pyrolysers are suitable. Typical pyrolysis temperatures:
- Micro‑furnace / Curie‑point: ~500–600 °C
- Platinum‑filament: ~600–750 °C
- Gas chromatography:
- Detector: flame‑ionization detector (FID) preferred (especially with capillary columns); thermal‑conductivity detector (TCD) acceptable.
- Columns: capillary or packed columns; non‑polar or semi‑polar silicone phases (e.g., polydimethylsiloxane, diphenyl or cyanopropylphenyl-modified) recommended to separate styrene, butadiene and isoprene.
- Typical operating parameters are provided (e.g., 30–60 m capillary columns, helium carrier gas, injector ~250 °C, FID ~300 °C).
- Data handling: Recorder, integrator or computer system to measure peak areas and calculate composition percentages relative to the sum of the three components.
- Quality notes: Use equal, small sample masses (usually 0.1–5 mg) for reproducibility; ensure identical test conditions for calibration and unknowns. Be aware of interfering peaks (e.g., isobutene proximity to butadiene).
Applications and users
- Practical applications:
- Quality control of styrene–butadiene–isoprene (SBR/BR/IR) rubbers and blends
- Verification of polymer composition for material specifications
- R&D and formulation development for rubber compounds
- Failure analysis and forensic polymer identification
- Who uses it:
- Rubber manufacturers and compounders
- Independent testing and certification laboratories
- Polymer analysts, QC chemists and R&D teams using pyrolytic GC
- Regulatory or procurement teams verifying material compliance
Related standards
- ISO 1407:2023 (referenced extraction procedure) - relevant for solvent extraction of oils/additives prior to py‑GC.
- This third edition replaces ISO 7270-2:2012 (minor revisions including updated normative references and CAS numbers).
Note: ISO 7270-2:2024 assumes users have working knowledge of gas chromatography and appropriate laboratory safety practices.
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