Isocyanates : Basics

Isocyanates have the following active functions (- N = C = O).

Even that the Isocyanates function has irritant effects on humans and other living creatures, they should not be confused with Cyanate: anion (OCN-) derived form the poisonous Cyanic Acid HCNO.

Isocyanates are essential factor to launch the reaction of producing Polyurethanes. Their reaction with Polyol in the presence of catalysts is fast, exothermic and total.

Isocyanates are a generic name for a group of chemicals having the NCO functions. The most notable Isocyanates are TDI (Toluene Di-Isocyanate), MDI (Methyl diphenyl Di-Isocyanate), Hexamethylene Di-Isocyanate (HDI), and IsoPhorone DiIsocyanate (IPDI).

Other types of Isocyanates form just 1.2% of total market. TDI and MDI form together 95.4 % of the Isocyanates market.

The dual functionality of the Di-Isocyanates along with the dual or triple functionality of the Polyol ensures the formation of the long chain polyurethane polymer.

The reaction between each Isocyanate group (- N=C=O) and an alcohol function (-O – H) results in a formation of the Urethane function as shown below:


R1 – N = C = O + R2 – OH -----------------> R1 – N – C OO – R2