Overview
ISO 21627-2:2009 specifies a laboratory method for the determination of easily saponifiable chlorine in epoxy resins. The measured value indicates the concentration of chlorine present mainly as 1,2-chlorohydrin groups formed during epoxy manufacture (epichlorohydrin-based resins). Results are used for impurity monitoring and quality control of epoxy materials.
The method uses saponification with sodium hydroxide in an organic solvent, followed by potentiometric titration of chloride with standardized silver nitrate solution. A correction is applied for any inorganic (ionic) chlorine determined separately using ISO 21627-1.
Key Topics
- Scope and purpose: Determines the quantity of chlorine that is easily saponifiable in a given epoxy resin sample; indicative of chlorohydrin impurities.
- Principle: Saponify organic chlorine with NaOH in 2‑butoxyethanol (epoxy resins) or in methanol at 50 °C (glycidyl esters). Acidify and measure resulting chloride ions by potentiometric titration with AgNO3.
- Reagents and safety: Uses analytical‑grade reagents and grade 3 water (ISO 3696). Notable reagents include 2‑butoxyethanol and methanol (both carry toxicity warnings), NaOH solutions, acetone and standardized 0.01 mol/l AgNO3. Silver nitrate must be standardized against dried NaCl and stored protected from light.
- Apparatus: Standard laboratory glassware plus a potentiometric titration setup with a silver/silver‑chloride electrode, analytical balance, water bath (50 °C), and magnetic stirring.
- Procedure highlights: Typical test portions are selected to limit easily saponifiable chlorine in the aliquot; saponification is carried out for 2 h (a 30 min shorter time may be used for QC if validated), followed by addition of ketone and acetic acid and immediate potentiometric titration.
- Results expression: Results are calculated from titration volumes, AgNO3 concentration and a correction for inorganic chlorine; values are reported in mg/kg and rounded to three significant figures.
Applications
- Quality control: Routine monitoring of chlorohydrin impurities in epoxy resins to ensure consistent product performance and to detect incomplete dehydrohalogenation.
- Process control: Evaluate effectiveness of dehydrohalogenation steps during resin manufacture.
- Regulatory and material specification: Provide documented impurity data for material specifications, supplier qualification and compliance records.
Related Standards
- ISO 21627-1: Inorganic (ionic) chlorine determination - required for the correction applied in this method.
- ISO 21627-3: Total chlorine determination in epoxy resins.
- ISO 4615: Analytical methods for other chlorine impurities in related resins.
Notes: The standard includes safety statements and detailed procedural parameters (reagent concentrations, volumes, times and temperatures). Interlaboratory precision data were not available at publication; users should follow the test report requirements and record any deviations from the prescribed procedure.
Open preview (PDF)Plastics — Epoxy resins — Determination of chlorine content — Part 2: Easily saponifiable chlorine