AdditionCuring

Addition curing is a type of polymerisation reaction where monomers add to each other in a way that forms a continuous chain. This process does not produce any byproducts or small molecules like water or alcohol. Instead, the molecules of the reactants combine directly to form the polymer. This is in contrast to condensation curing, which releases small molecules as a byproduct.

Addition curing is often used in the creation of silicones and polyurethanes. In the case of silicones, a platinum catalyst is typically used to facilitate the reaction between vinyl-terminated silicones and hydride-terminated silicones. This results in a crosslinked network that gives the silicone its elastic properties. For polyurethanes, the reaction involves an isocyanate and a polyol, which combine to form urethane linkages.

The primary advantage of addition curing is that it is a "clean" reaction, meaning no byproducts are formed. This can be important for applications where purity is critical, such as in medical devices or food-grade materials. The reaction is also generally faster than condensation curing, and the resulting polymers often have excellent mechanical properties, including high strength and elasticity. However, addition curing can be sensitive to impurities that can inhibit the reaction. The rate of cure can also be influenced by temperature.