The Behaviour of Commercially Important Di-isocyanates in Fire Conditions Part 1: Toluene Di-isocyanate (TDI)

Several di-isocyanates have become commercially important materials, used as intermediates in the manufacture of a wide variety of polyurethane products, yet little is recorded on their behaviour if involved in fire. This paper describes a series of programmes carried out under the auspices of the International Isocyanate Institute Inc. First, a small scale laboratory investigation of the ignition, heat release, smoke and toxic gas production characteristics of di-isocyanates was carried out. Second, their behaviour in drumstock and pool fires, respectively, was examined, using full-sized samples and selected real-fire scenarios. Part 1 records the results for toluene di- isocyanate (TDI) showing the need for a modest energy input to ignite it from a pilot flame. It then burns in a steady rather than vigorous manner, leaving no residues. Toxic gases evolved are mainly carbon monoxide, while free isocyanate is likely in the early stages of the fire, and hydrogen cyanide may be important in well-developed fires. Drumstock material behaviour in a fire is dictated mainly by the rupture characteristics of the containers, which can be violent. A series of simple guidelines is suggested, which includes the need for firefighters to wear full protective clothing and fresh-air breathing equipment. It is also recommended that drumstock TDI should be stored away from easily ignitable materials.