This was the first “polymer” made for coatings, as it was synthesized using three monomers: phthalic anhydride, glycerol, and linoleic acid (Figure 2). What resulted from this work was the development of the first alkyd paint system. Paint chemists in the 1930s wondered if somehow they could find a binder system for paint that provided both productivity and the inherently better appearance of a natural oil resin.
Nitrocellulose paint was highly productive, but the final coating required polishing to achieve high gloss. Early Automotive Coatings Chemistries: From Alkyds to Acrylic Lacquers This article is intended to provide a brief historical survey of the evolution of automotive coatings technology. In fact, many of the new technologies and chemistries in coatings science have come from advances pioneered in the automotive coatings field. Since that first new technology advance in the 1920s, innovations in automotive coatings technology have continued unabated. In this case, the need for improved productivity in the automotive plant drove the invention and development of a new coating chemistry. This was the first example of how industry needs have driven the advance of automotive coatings technology. Some formulation development work by the paint chemists found that this new synthetic lacquer resin provided an excellent basis for a paint that had improved appearance, toughness, and durability versus natural oil resin paints, and also could be easily pigmented with a wide variety of color pigments, besides just black! After a couple of years of testing, in 1924 General Motors introduced the use of Duco finishes on almost their entire automotive line. Being a lacquer, this coating dried (merely through solvent evaporation) in about two hours.
The DuPont chemists who had used nitrocellulose chemistry (Figure 1) to develop explosives and motion picture film found that if they modified the molar ratio of the NO 2 groups in the cellulose backbone, they obtained a low viscosity lacquer resin at about 15% resin solids that could be spray applied as a coating.
This new coating technology made a step change in productivity by reducing the painting and drying time from many days to a few hours. This process bottleneck was the motivation for the first paint specifically developed as an automotive coating: DuPont Company’s “ Duco” paint. Model Ts undergoing the painting process at the end of the assembly line jammed warehouse floors of the automotive plant. This caused a terrible production bottleneck for Ford’s innovative mass production process, even though the black paint dried faster than all other available colors. Ford’s black paint was applied by hand brushing to the Model T in multiple coats, a process that, in the end, took about a week to complete. Oil resins cure through oxidative crosslinking, which means the paint takes a long time to dry. Of course, the black car paint that Ford put on his Model T actually was not “automotive” paint at all, but just the existing paint technology available at the beginning of the 20th century: a paint based on natural linseed oil resin as the binder. In 1908, Ford thought that black car paint was the only practical automotive paint for the Model T, as it provided him with a coating that was both durable and cheap in cost. The oft-quoted statement above of Henry Ford is humorous today, but Ford was serious when he said it. “The customer can get the Model T painted in any color he wants, so long as it’s black!”-Henry Ford, 1908. Lamb, Coatings Consultant The Birth of Automotive Coatings