Special amines and stannous salts are used as catalysts in the foam manufacturing, which speeds up the main reactions and are considered to be blowing agents for gelling reaction between TDI and water, which generates carbon dioxide, as well as gelling agents in the reaction between polyol and TDI functional groups.

They are used in a small amount, but are very important, with big impact to any change in the formulation, therefore choosing the right catalysts and ratio is crucial in flexible foam manufacturing.