Polyurethanes

Chemistry

Polyurethanes are produced by reacting diisocyanates with polyols, often in the presence of a catalyst, or upon exposure to ultraviolet radiation. Common catalysts include tertiary amines, such as DABCO, DMDEE, or metallic soaps, such as dibutyltin dilaurate. The stoichiometry of the starting materials must be carefully controlled as excess isocyanate can trimerise, leading to the formation of rigid polyisocyanurates. The polymer usually has a highly crosslinked molecular structure, resulting in a thermosetting material which does not melt on heating; although some thermoplastic polyurethanes are also produced.