31 Development and Characterization of a Generation System for Airborne Diisocyanates

Abstract Diisocyanates are fast-reacting semi-volatile compounds and one of the main components in the production of polyurethane-based materials. They are known as a predominant causal agent of occupational asthma. Discrepancies within well-documented and validated methods were observed and factual explanations of these discrepancies are not yet available. A more in-depth investigation of isocyanate measurement methods' efficiencies should be undertaken. The objective of this study was to develop a system capable of generating diisocyanate vapor and fine particle atmospheres with control of parameters such as concentration levels and vapor/particle partitioning. Two generation approaches were used: nebulization and heating. A controlled air flow (RH and T°) was combined to the generator's effluent in a mixing chamber and transferred, downstream, to an exposure chamber. A splitter collected eight samples simultaneously. The isocyanate measurement method used a glass fibre filter with 9-methylaminomethyl-anthracene (GF+MAMA). The particles were analyzed using a particle analyzer (Fidas Frog) and the particle size distribution of the isocyanates was obtained using a Marple impactor. Diphenylmethane-4,4'-diisocyanate (MDI) was generated with both generation approaches. The system was able to generate stable concentrations over time at different levels (5 to 50 µg/m3). Intratest variability was lower than 10% (RSD). By cross-referencing the data obtained by the particle counter and the Marple impactors, it was possible to document the particle-size distribution and vapor/particle partitioning of the MDI generated within the parameters used. The versatility of this system makes it a highly promising tool for assessing the performance of different diisocyanate measurement methods.