Quaternary Ammonium Polyurethane Trimerization Catalysts: Delayed Action Mechanisms and Product Parameters Abstract: Polyurethane (PU) foams, coatings, adhesives, sealants, and elastomers find widespread applications due to their versatile properties. The trimerization of isocyanates to form isocyanurate (PIR) rings offers enhanced thermal stability and flame retardancy to PU formulations. Quaternary ammonium salts (QAS) are commonly employed as...