Polyurethane Trimerization Catalysts in Spray-Applied Polyisocyanurate (PIR) Insulation Technology: A Comprehensive Review Abstract: Spray-applied polyisocyanurate (PIR) insulation represents a significant advancement in thermal management for building and industrial applications. The formation of PIR foam relies heavily on the efficient trimerization of isocyanates, a reaction accelerated by specific catalysts. This article provides a comprehensive review of...