OPTIMIZATION OF CONDITIONS FOR TITRIMETRIC DETERMINATION OF ISOCYANATES IN POLYURETHANE SYSTEMS

Metrological characteristics of two methods were compared to control the content of isocyanates in the pre-polymer based on methylene diphenyl diisocyanate (Wannate 6901, China): titrimetric — based on the reaction of interaction of isocyanate group with diethylamine, followed by titration of excess of the latter with hydrochloric acid in the presence of bromphenol blue and spectrophotometric — based on the reaction of the analyte in dimethylformamide with ammonia solution of sodium nitrite (λ = 440 nm). Spetrophotometric analysis in the linear range of 6–12 mg/mL showed good reproducibility (sr = 0.002).