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Hazards of Isocyanates (TDI, MDI, HDI) In Resins, Coatings and Paints

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 info@atlenv.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

November 8, 2018

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. Isocyanates cause a polymerization rather than a solvent drying process, which can result in health problems of its own. This sadly is trading one problem (solvents) with another (isocyanates).

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. What this means is that if the mixture of isocyanate and the resin are blended properly, all the isocyanate is reacted and no residual should exist-and no isocyanate exposure should exist. In most situations this is the case-but not all. 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.

The testing for isocyanate is well within our capabilities and includes years of sampling and assisting in reducing or eliminating isocyanate exposure.

If interested in further information, call us at 1-800-344-4414 or e-mail us at info@atlenv.com.

Our primary service areas for Resins and Isocyanates Services are: NJ, NY, NYC, PA, CT, DE, (Boston) MA, RI, Wash DC, WI, MD, MI, (Chicago) IL, VA, IN, (Atlanta) GA, AL, NC, SC, TN, (Dallas, Ft Worth) TX, OK, DC, AR, we can service most other areas of the U.S. but with some added travel charges.

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