Overview
EN 1242:2013 (CEN) - "Adhesives - Determination of isocyanate content" - specifies a standardized chemical test method for measuring the isocyanate content (-NCO) of adhesives, adhesive components and their basic constituents. The method is intended for raw materials and formulated adhesives except products containing blocked isocyanate groups that can be liberated by the test reagents. This European Standard replaces EN 1242:2005 and clarifies reagents (notably the inclusion of ethanol) and procedural requirements.
Key topics and technical requirements
- Principle: Reaction of isocyanate groups with an excess of dibutyl amine in an aprotic solvent (typically toluene) to form urethanes; unreacted amine is back-titrated with hydrochloric acid. End-point detection via bromophenol blue indicator or potentiometric titration.
- Reagents: Dibutyl amine solutions (1.0 M and 0.2 M), dry toluene (or alternative solvents when needed), acetone, methanol, ethanol, bromophenol blue indicator, HCl solutions.
- Apparatus: Class A volumetric glassware (pipettes, volumetric flasks, burettes), analytical balance (0.1 mg), microburette, potentiometric titration electrodes (optional).
- Procedure highlights:
- Sample preparation per EN ISO 15605 and EN 1067.
- Dissolve sample in toluene (add acetone if insoluble), react with measured dibutyl amine, dilute with methanol, then back-titrate.
- Run a blank and at least two determinations; report mean value.
- Calculation: % NCO calculated from titration volumes, acid molarity and test portion mass (formula and variables provided in the standard).
- Precision: Maximum allowable deviations depend on %NCO range (e.g.,
