p-Toluenesulfonyl isocyanate
A fast-acting chemical moisture scavenger that removes water from polyurethane components before it can make bubbles.
p-Toluenesulfonyl isocyanate is a monofunctional, highly reactive sulfonyl isocyanate (formula C₈H₇NO₃S). It is a liquid supplied for use as an additive.
PTSI is added to solvents, pigment dispersions, polyols and B-side blends of polyurethane coatings and sealants to scavenge water before the isocyanate hardener is added, reducing CO₂ gassing, pinholes and loss of pot life.
PTSI reacts with water far faster than ordinary isocyanates, forming p-toluenesulfonamide and carbon dioxide. Because it releases CO₂, it is used in components where the gas can escape before application, typically during manufacture.
PTSI is corrosive and reacts violently with water; it is also a respiratory sensitizer like other isocyanates. Handle in dry conditions with full protective equipment, and keep containers tightly sealed.
PTSI acts chemically and fast but releases CO₂. Molecular sieves trap water physically without gas, which suits components that will be sealed or used later.
It is normally used by manufacturers during production because of its reactivity and hazards.
