Isocyanates - methodology for gas and particle generation, sampling and detection

Abstract: Isocyanates are mainly used in the industry for the production of polyurethane (PUR) plastics. Workers are at risk of being exposed during the manufacturing of PUR. During thermal degradation of PUR, isocyanates are released and workers involved in hot work such as fire-fighting, welding etc. may also be exposed.Isocyanates are known to cause allergic diseases and are the most common cause of occupational asthma. Some of the isocyanates used are suspected human carcinogens. Exposure among workers occurs frequently.Isocyanates are reactive unstable compounds that need to be converted to stabile derivatives immediately during sampling to avoid underestimation of the exposure. Di-n-ButylAmine (DBA) was used as derivatising reagent to form stable urea derivatives. The DBA derivatives were analysed using LC-MS/MS.In this thesis a novel technology for the direct monitoring of isocyanates using a Proton Transfer Reaction Mass Spectrometry (PTR-MS) is presented. Advancement of technology for the generation of isocyanates in an environmental chamber, dry sampling, particle-size fractionated sampling and the testing of respirator filter cartridges are described.The dry sampler was demonstrated to be robust and enabled sampling up to 32 h. Precise sampling without the need of field extraction was made possible.The particle-size fractionated sampling efficiently separated gas-phase and respirable particle-borne isocyanates (< 4µm in diameter).Two personal protective respirator filter cartridges were studied. No trend of impaired performance for mono-isocyanates throughout 48-h exposure tests was found.The distribution patterns, in a steady-state tube-furnace oven, between gas phase and different particle-phase fractions of isocyanates produced in fires were investigated. The substantial degradation of a PVC-carpet containing PUR and a wood board with a MDI based binder resulted mainly in the formation of high levels of monoisocyanates.