The term “2K paint” is used frequently now to describe certain finishes including many automotive paints. Basically, paints that have an activator, catalyst, or hardener required for use are described as two component since they have a 2nd component required to work properly. As a rule finishes that require only a thinner are not considered 2K since thinner is simply for improving application properties and not integral to the cure process. Much of the early use and development of these finishes was in germany where the term 2 “Komponenten” was used to describe these and eventually was shortened to “2K” over time. Obviously, 2K is a lot easier to say and write than “Komponenten”.
Two component chemistry sees wide application in automotive refinish coatings due to superior durability and appearance properties obtainable at ambient temperature cure. Previously, finishes of comparable performance required high bake temperatures to cure which was not always possible outside a factory environment and certainly not preferable in any environment. The two parts in 2K finishes physically react with each other at normal ambient (room) temperatures and must be kept separated until just prior to use in order to make an effective finish. Once mixed the blend has a only a limited time of usefulness which is referred to as its “pot life” and often ranges from 2 hours to 8 hours depending on the temperature and formulation of the finish. As soon as the two components are mixed the blend slowly begins to increase in viscosity until ultimately it becomes too thick to be useful and ultimately will gel and form a solid or semi-solid block.
As we mentioned earlier, compared to 1K (one component) enamel or lacquer automotive finishes, 2K finishes generally exhibit greater appearance and/or durability. The basis for the enhanced performance is the formation of highly cross-linked networks of molecules that are physically bound together. Depending on the formulation the resulting molecules can be infinitely larger in cured 2K finishes than 1K enamel or lacquer finishes.
Common 2K finishes include epoxy primers, urethane primers, urethane topcoats and urethane clear coats. The urethane linkage created during the reaction of the two components, polyols and isocyanates, has gained wide use in the automotive industry due to their outstanding performance properties and wide versatility.