Diisocyanates - Introduction
What are Diisocyanates?
There are many types of diisocyanates, the foremost of which are methylene diphenyl diisocyanate (MDI), Toluene diisocyanate (TDI) and hexamethylene diisocyanate (HDI). Along with polyols, these chemicals form the building blocks of polyurethane. Polyurethane is effectively derived from the chemical reaction between diisocyanates and polyols; when mixed together they polymerise. It is the material of choice for a broad range of end-user applications such as insulation, paints, glues and resins.
Diisocyanates enter the body primarily through inhalation and skin exposure.
They are potent respiratory and skin sensitisers and a common cause of asthma and allergic contact dermatitis. There is evidence that both respiratory and dermal exposures can lead to sensitization. A range of other adverse health effects are also associated with diisocyanate exposure including irritation to the mucous membranes of the eyes and gastrointestinal and respiratory tracts.
Control of exposure
Where diisocyanates are used or unintentionally generated, for example when polyurethanes are heated, it is important that workers’ exposures are properly controlled. There are various ways of achieving this, and the way that the diisocyanate is used or generated often dictates which control strategy is needed. All exposure controls require maintenance if they are to remain effective. Further information is available here. (This information sheet is in the process of being updated).
Diisocyanates are also regulated under the Construction Products Directive and General Products Safety Directive but these are outside the remit of the Authority . See https://www.echa.europa.eu/web/guest/legislation-obligation/-/obligations/100.318.722
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