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HISTORY
FROM RESIN TO GLORY Automotive coatings through the ages BY SOPHIE PRICE
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n the beginning, the only paint available for automobiles was based on natural linseed oil resin. Since then, we have come a long way from the oil resin—cured through oxidative crosslinking, which required large amounts of time for the paint to dry fully. We have found solutions to the production bottleneck, and it all traces back to the first-ever automotive paint coating, invented by DuPont Company in the 1920s. Duco Paint, which was invented by DuPont Company significantly reduced the amount of time it took for the paint to dry going from taking days to simply hours. To speed the process up even more DuPont chemists found that if they obtained a low viscosity resin at around 15 percent solids, it could be sprayed on as a coating. This makes the paint a lacquer and allows it to dry through solvent evaporation in only 2 hours. This also improved appearance,
toughness, durability and allowed for multiple colours. Although the paint was highly productive the final coat required polishing to achieve high gloss. In the 1930s paint chemists began to wonder whether they could find a binder system for paint that could provide both productivity and the preferred appearance of a natural oil resin. From this came the first alkyd paint system. This was the first “polymer” made for coatings, as it was synthesized using three monomers: phthalic anhydride, glycerol, and linoleic acid. Alkyd chemistry continues as a mainstay of current coating technology.
DuPont Company invented the first automotive paint coating in the 1920s.
1950S Automotive coatings saw further growth by the 1950s. Rohm and Haas Co. had just developed a new synthetic polymer as a glass replacement based on poly methyl methacrylate, and the industry began to investigate whether that technology could be used in coatings. This would go on to be the first all man-made resin technology to be used in automotive coatings. Thermoplastic acrylic resin technology would then go on to dominate the automotive topcoat
market in automotive coatings for two decades. This coating however, needed to be sprayed on at relatively low solids of about 20 percent. This meant that multiple coats of the topcoat had to be applied to reach the desired film build of about two mils. It did, however, provide an excellent binder system for the newest pigment colourant technology-metallic pigments. The metallic pigments provided brilliant, shiny car colours
The 1950s saw Rohm and Haas Co. develop a new synthetic polymer that would go in to become the first all-man-made resin technology in automotive coatings.
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that enhanced the car body. To achieve the best visual effects the pigments must align parallel to the painted surface. The rheological profile of an acrylic lacquer paint is perfect to obtain this effect: a low initial viscosity to allow the metallic flakes to lay flat, and a fast rise in viscosity to keep the flakes in place. This technology had such a strong advantage that by the 1960s General Motors painted almost every car with acrylic lacquer topcoats.
Automotive coatings saw further growth by the 1950s. Rohm and Haas Co. had just developed a new synthetic polymer as a glass replacement based on poly methyl methacrylate, and the industry began to investigate whether that technology could be used in coatings.
