Test atmospheres of diisocyanates with special reference to controlled exposure of humans
An all glass apparatus for the generation of air concentrations of 2,4-toluene diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI) and 1,6-hexamethylene diisocyanate (HDI) was deveoped. The generation principle was based on gas-phase permeation with permeation membranes of silicon rubber. In an 8 m3 stainless steel test chamber, low and steady TDI- and HDI atmospheres (1-100 μg/m3) could be maintained. The diisocyanate concentrations were determined by an HPLC method, using the 9-(N-methylaminomethyl)-anthracene reagent utilizing UV detection. The sum of diisocyanates and their related amines were determined by sampling in 0.4M hydrochloric acid solution, and analysis by capillary gas chromatography with thermionic specific detection. Related amines were determined by sampling in ethanol — 0.2% KOH and analysis on GC-TSD. A continuous band-tape monitor was used for the determination of diisocyanates. Losses of diisocyanates in the test chamber were evaluated by measuring the TDI and HDI concentrations at the inlet respectively the outlet of the test chamber. At the outlet of the test chamber, ca 25% of the TDI respectively HDI concentrations were recovered. With a male subject in the test chamber ca 15% of the HDI concentration was recovered. The air flow through the test chamber was ca 10 M3 /h. The changes in isomeric composition of airborne TDI, at stopped flow conditions, showed that the decay of the 2,4-isomer was faster than of the 2,6-isomer. No trace of the related amine toluene diamine (TDA) was detected in the test chamber, at TDI concentrations ranging from 20 to 50 μg/m3. Sampling losses due to sampling connections were evaluated. No losses for TDI and HDI were obtained with 150 mm impinger tubings of glass, teflon or stainless steel. Sampling losses ranging from ca 30 to 80% for TDI and ca 35 to 65% for HDI, were caused by tubings of silicone rubber, latex, polypropene and polyvinylchloride.
Key wordsDiisocyanates Test atmospheres Sampling connections Human exposure
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