What it is
Castor Oil/IPDI Copolymer is a polyurethane-type polymer formed by crosslinking castor oil with isophorone diisocyanate (IPDI). The reaction consumes the reactive isocyanate groups, leaving a stable, flexible polymer used to form continuous films. In sunscreens, skin tints, and color cosmetics it helps deposit pigments and filters in an even layer and improves the wear and uniformity of the finish.
Safety & warnings
The finished copolymer is a high-molecular-weight, cured polymer in which the reactive isocyanate groups have been consumed, and it is used as a stable film former rather than a free monomer. As with other film-forming polymers, it is generally well tolerated at cosmetic use levels.
Origin & sourcing
Synthetic; a copolymer derived in part from castor oil (a plant oil) and IPDI, a synthetic diisocyanate crosslinker.
Questions everyone asks
Does this contain free isocyanate?
No. The IPDI reacts during manufacture to form the finished polymer, so the cosmetic ingredient is a cured film former rather than a free reactive monomer.
What is it used for in sunscreen?
It forms a flexible film that helps deposit pigments and UV filters evenly and improves the uniformity of the finish.