If you need isocyanates (TDI, MDI, HDI) testing/sampling as discussed in this article call us at 1-800-344-4414 or email us at email@example.com for details and a free estimate.
Written by Henry P. Shotwell, Ph.D., CIH, Vice-President and Robert E. Sheriff MS, CIH, CSP, President
June 21, 2016
Polyurethanes are polymers that are formed by reacting an isocyanate, like TolueneDiIsocyanate (TDI), Methylene Bisphenyl Isocyanate (MDI) or Hexamethylene Di Isocyanate (HMDI) (also referred to as HDI) and an alcohol. These polymers are used to make foam padding for mattresses and seat cushions, gaskets and seals, adhesives, paints, surface coatings and sealants and synthetic fibers like Spandex®. The effort to reduce or eliminate solvent in paints and coating has led to a problem with isocyanates. The chemicals cause a polymerization rather than a solvent drying process, which can result in health problems of its own.
Isocyanates can be aromatic, like TDI and MDI, or aliphatic like HDI. The aromatic isocyanates (TDI and MDI) are more reactive and more economical to use than aliphatic HDI. Depending on the type of isocyanate, the type of alcohol, catalysts and other additives used, a wide variety of products can be formed.
A fully reacted polyurethane is chemically inert and contact with it will not produce harmful effects. Polyurethanes are combustible, however, and will ignite if exposed to open flame, producing carbon monoxide in the process. The isocyanates (TDI, MDI and HDI) are well-known skin and respiratory sensitizers and irritants. TDI is considered to be a carcinogen by NIOSH. Workers who are engaged in production of polyurethane polymers and who have potential exposures to the liquid resin and isocyanate ingredients need to use the engineering controls, personal protective equipment and good hygiene practices specified by manufacturers and by Safety Data Sheets (SDS).
OSHA has set a ceiling limit for MDI (Methylene Bisphenyl Isocyanate) at 0.02ppm and a ceiling limit for TDI (TolueneDiIsocyanate) at 0.02ppm – See 29 CFR 1910.1000 Table Z1 at http://www.osha.gov/law-regs.html.
The real danger with isocyanates is that a small percentage of people develop a respiratory sensitivity to them. The result is a severe asthmatic reaction. Once sensitized, the individual will have asthmatic reactions at extremely low levels of airborne isocyanates, so much so that they generally can’t work around them at all. Some people are so sensitive that entering a paint store or an auto garage will trigger a reaction.
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