Overview
ISO 21048:2014 - Plastics - Epoxy resins - Determination of 1,2-glycol content specifies a standardized analytical method to measure the 1,2-glycol (vicinal dihydroxyl) content in epoxy resins. The method is important because 1,2-glycol impurities, formed during epichlorohydrin-based production, are hydrophilic and can affect electrical insulation, curing speed with amines or anhydrides, and final resin performance. This second edition (2014) replaces ISO 21048:2004 and defines reagents, apparatus, procedure, calculation, precision and reporting requirements for laboratory quality control and materials testing.
Key topics and technical requirements
- Principle: Oxidation of 1,2-glycol with orthoperiodic acid to generate iodine via an iodometric sequence; the liberated iodine is titrated with standardized sodium thiosulfate. The 1,2-glycol content is calculated from titrant consumption.
- Reagents: Chloroform, methanol, benzyltrimethylammonium hydroxide, orthoperiodic acid (0.2 mol/L prepared and neutralized to pH 7), sulfuric acid (10%), potassium iodide (20%), sodium thiosulfate (0.1 mol/L, standardized), starch indicator and oxygen‑free water (ISO 3696 grade 3).
- Apparatus: Analytical balance (0.1 mg), magnetic stirrer, pH‑meter (±0.1 pH), burette (50 mL), pipettes and volumetric glassware.
- Procedure highlights: Select test portion mass based on expected 1,2-glycol level (e.g., 10 g for w
