Isophorone diisocyanate
A cycloaliphatic diisocyanate with two NCO groups of different reactivity, widely used for light-stable prepolymers and waterborne polyurethane dispersions.
Isophorone diisocyanate (IPDI) has one NCO group attached directly to a cyclohexane ring and another on a methylene group, with methyl substituents on the ring. Its molecular weight is about 222.3 g/mol, giving 37.8% NCO. It is a colorless to pale-yellow liquid.
IPDI is used where light stability and controlled reactivity are needed:
The two NCO groups are structurally different and react at different rates, which lets chemists cap one group selectively and build prepolymers with narrow molecular weight distribution and little free monomer. As a cycloaliphatic isocyanate it gives non-yellowing films. IPDI has also been microencapsulated for moisture-triggered self-healing coatings.
IPDI is a respiratory and skin sensitizer and must be handled with the same controls as other diisocyanates. Store sealed under dry conditions to prevent moisture reaction.
Its controllable, relatively slow reactivity and light stability suit prepolymer processes used to make polyurethane dispersions.
Yes. Like other aliphatic and cycloaliphatic isocyanates, it does not form the colored products that make aromatic polyurethanes yellow.
