Trimerization

A third reaction, particularly important in making insulating rigid foams is the isocyanate trimerization reaction, which is catalyzed by potassium octoate, for example.

Bönnemann cyclization Bönnemann cyclization The trimerization of a part of a nitrile molecule and two parts of acetylene into pyridine is called Bönnemann cyclization.

Factors affecting catalyst selection include balancing three reactions: urethane (polyol+isocyanate, or gel) formation, the urea (water+isocyanate, or "blow") formation, or the isocyanate trimerization reaction (e.