A catalyst is a substance that speeds up the rate of a chemical reaction without being consumed by the reaction. In the case of polyurethane reactions, catalysts are used to accelerate the formation of polyurethane polymers from isocyanates and polyols.

There are many different types of catalysts that can be used in polyurethane reactions. The most common types are amine catalysts. Amine catalysts are effective in catalyzing the reaction between isocyanate and hydroxyl groups, which is a key step in polyurethane formation. Amines are also used to control end product properties such as hardness, flexibility and water resistance.

Other types of catalysts that can be used in polyurethane reactions include organometallic catalysts, metal carboxylates, and enzymes. An organometallic catalyst is a catalyst that contains metal atoms. They are commonly used in the production of polyurethane foam. Organometallic catalysts can be used to control reaction rates, properties of end products, and the environmental impact of manufacturing processes.

A metal carboxylate is a catalyst containing a metal atom and a carboxylate group. They are commonly used in the production of polyurethane coatings. Metal carboxylates can be used to control reaction rates, properties of final products, and the environmental impact of manufacturing processes.

Enzymes are biological catalysts that can be used to catalyze a variety of chemical reactions, including polyurethane reactions. Enzymes are often more selective than other types of catalysts, meaning they can be used to more precisely control the properties of the final product.

Choosing a catalyst for a particular polyurethane application depends on many factors, including the desired properties of the final product, the cost of the catalyst, and the environmental impact of the manufacturing process.