Overview
ISO 7725:2020 - Rubber and rubber products - Determination of chlorine and bromine content - specifies laboratory methods to quantify chlorine and bromine (halogen) content in raw, vulcanized and unvulcanized rubber. The standard covers natural rubber and common synthetic rubbers (isoprene, SBR, BR, butyl and halogenated butyl, nitrile, EPDM, chloroprene and epichlorohydrin). It defines sample-preparation routes and two analytical approaches: ion chromatography (IC) and potentiometric titration.
Key topics and technical requirements
- Scope and materials: Applies to raw rubber and rubber compounds; detects halogens present in polymer chains, additives or contaminants.
- Sample preparation (normative): Three combustion-based methods to convert sample to analysable solution:
- Tubular furnace combustion (Annex A)
- Oxygen combustion flask (Annex B)
- Oxygen combustion bomb (Annex C)
Two independent solutions per sample are required.
- Analytical methods:
- Method A - Ion chromatography (Clause 6): Uses certified chloride/bromide standards, eluent and anion-exchange columns with conductivity detection (optionally with a suppressor). Preferred for very low halogen levels because of higher sensitivity.
- Method B - Potentiometric titration (Clause 7): An established wet-chemistry titration route improved in this edition; suitable for routine determinations where titration end-points are well-defined.
- Calibration and calculation: Calibration curves from multiple standard concentrations are required. Results are calculated from sample and blank concentrations and reported as % mass of chlorine or bromine.
- Precision, reporting and safety: The standard specifies precision data (Clause 8) and test-report content (Clause 9). Warnings emphasize normal laboratory practice and environmental/safety handling of combustion and reagents. Hazardous reagents (e.g., mercury nitrate, hydrazine) have been removed from this edition.
Practical applications and typical users
- Quality control in rubber product manufacturing - verify halogen levels for performance and compatibility (e.g., flame-retardancy, vulcanization behavior).
- Incoming raw-material inspection for natural and synthetic rubber batches.
- Failure analysis and R&D - identify halogen-related degradation or contamination.
- Regulatory and environmental testing - monitor halogenated compound presence for compliance.
Typical users: analytical laboratories, rubber compounders, OEMs, material scientists, and regulatory testing labs.
Related standards (referenced)
- ISO 1795 - Sampling of raw rubber
- ISO 4661-2 - Preparation of samples and test pieces for chemical tests
- ISO 3696 - Water for analytical laboratory use
Keywords: ISO 7725:2020, chlorine and bromine determination, rubber testing, halogen content, ion chromatography, potentiometric titration, sample combustion methods.
