Overview
ISO 1408:1995 - "Rubber - Determination of carbon black content - Pyrolytic and chemical degradation methods" specifies laboratory procedures to measure carbon black in vulcanizates and rubber copolymers. The standard defines a preferred pyrolytic method (Method A) and two chemical degradation methods (Methods B and C). Results are obtained gravimetrically by removing organic polymer and weighing the residue before and after oxidation of carbon black. Safety and normal laboratory practice are emphasized.
Key topics and requirements
- Scope and applicability
- Covers artificial rubbers and copolymers. Replaces the 1987 edition with minor revisions.
- Method A (pyrolytic) is preferred for many rubbers (e.g., polyisoprene, polybutadiene, styrene-butadiene, butyl, acrylate, ethylene‑propylene types, silicone, polyethylene‑derived polymers) except where certain additives (lead/cobalt salts, graphitic blacks, resins, bitumen, cellulose) create pyrolytic residues.
- Method B (chemical degradation) is intended chiefly for samples not amenable to pyrolysis and for most unsaturated rubbers; uses nitric acid oxidation.
- Method C is relatively hazardous (uses tert‑butyl hydroperoxide after swelling in p‑dichlorobenzene) and is reserved for samples such as isobutylene‑isoprene copolymers and ethylene‑propylene copolymers when A and B fail.
- Not applicable to chloroprene rubbers or nitrile butadiene rubbers with >30% acrylonitrile.
- Principles and key steps
- Solvent extraction (acetone; dichloromethane if bitumen present) to remove soluble organic matter.
- Method A: pyrolysis of extracted sample in nitrogen at ~850 °C, cool and weigh residue, then combust residue in oxygen at ~850 °C; mass loss = carbon black.
- Method B: oxidative digestion with nitric acid, filtration (Gooch crucible), drying in nitrogen at 850 °C, then oxidize and reweigh.
- Method C: swelling followed by peroxide oxidation, filtration and heat treatments similar to other methods.
- Apparatus and reagents: combustion boat, tube furnace, muffle furnace, Gooch crucible, acetone, dichloromethane, nitric acid, controlled nitrogen/oxygen flows, etc.
- Health & safety: many corrosive and flammable reagents; operations require fume hood, PPE; Method C is especially hazardous.
Applications and users
- Quality control and incoming inspection in rubber manufacturing and compounding
- Materials testing labs and third‑party certification bodies assessing filler loading
- R&D and failure analysis in polymer science and tyre, hose, seal manufacturers
- Regulatory or contract testing where quantified carbon black content is required
Related standards
- ISO 1407 - Rubber - Determination of solvent extract (sampling/extraction apparatus)
- ISO 383 - Laboratory glassware - Interchangeable conical ground joints
- References to other analytical standards (e.g., ISO 5478) are cited for related procedures
Keywords: ISO 1408:1995, carbon black content, rubber testing, pyrolytic method, chemical degradation, tube furnace, Gooch crucible, acetone extraction, nitric acid oxidation.
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