Overview
EN ISO 21627-1:2009 - Plastics - Epoxy resins - Determination of chlorine content - Part 1: Inorganic chlorine describes a standardized laboratory method to determine the amount of ionic (inorganic) chlorine present in epoxy resins. Published by CEN/ISO, this part specifies a direct potentiometric titration procedure using standardized silver nitrate solution. Results are reported as milligrams of chlorine per kilogram of epoxy resin (mg/kg). The document replaces the 2003 edition and is one part of the ISO 21627 series (Parts 1–3).
Key topics and requirements
- Scope and purpose: Measurement of inorganic (ionic) chlorine in epoxy resins, important because chlorine impurities can affect cured-resin performance.
- Analytical principle: Direct potentiometric titration of a resin solution with 0.002 mol·L⁻¹ silver nitrate in 2‑propanol; endpoint determined from the inflection in the potential vs. volume curve.
- Reagents and solvents: Recommended reagents include acetone (or alternatives like MEK/THF if needed), 2‑propanol, glacial acetic acid, and grade‑controlled water per ISO 3696.
- Apparatus: Potentiometric titration setup with a glass–silver/silver chloride electrode, microburette, magnetic stirrer and analytical balance (0.1 mg resolution).
- Sample preparation and procedure: Typical test uses ~10 g resin dissolved in acetone, addition of water and acetic acid, followed by controlled addition of silver nitrate with potentiometric monitoring and a concurrent blank.
- Calculation and expression: Chlorine content calculated from titration volumes, silver nitrate concentration and sample mass; result rounded to one decimal place (mg/kg).
- Quality and precision: Method validated through an interlaboratory study (10 labs) per ISO 5725-2; outliers were removed from the precision analysis.
- Safety: Standard includes laboratory safety notice-users must follow normal lab practices.
Applications and who uses it
- Epoxy resin manufacturers: routine quality control, batch release and process control to limit ionic chlorine that may impair cured properties.
- Independent testing and QC laboratories: compositional analysis and supplier verification.
- R&D teams: formulation troubleshooting and impurity tracking during synthesis (epichlorohydrin-based routes).
- Procurement/specification writers and regulatory bodies: defining acceptance criteria for chlorine impurities in material specifications.
Practical benefits include consistent, reproducible measurement of ionic chlorine for product quality assurance, supplier comparison and compliance testing.
Related standards
- ISO 21627-2 - Easily saponifiable chlorine (organic types such as 1,2-chlorohydrin)
- ISO 21627-3 - Total chlorine
- ISO 3696 - Water for analytical laboratory use (grade specification)
- ISO 4615 - Methods for other impurities in epoxy resins
- ISO 5725-2 - Precision of measurement methods (interlaboratory studies)
Keywords: EN ISO 21627-1:2009, epoxy resins, inorganic chlorine, ionic chlorine, potentiometric titration, silver nitrate, chlorine content, quality control.
