This coatings have been manufactures by alkyd resins.

Alkyd resins are prepared from polyols, dibasic acid, and fatty acids. The term alkyd is derived from alcohol and acid.alkyds

Comparison of some unsaturated C18 fatty acids. The C=C bonds are chemical groups which react with oxygen and change the liquid oil to a solid

Typical polyester reaction

A theoretical alkyd prepared from 1 mol each of glycerol, PA, and fatty acid would have an oil length of about 60.

Glycerol-Phthalic Anhydride-Fatty Acid Alkyd Resin

There are many type classification of alkyd.one classification is based on oil length of an alkyd .oil length of an alkyd is calculated by dividing the amount of "oil" in the final alkyd by the total weight of the alkyd solids

Classification and properties of Alkyds by Oil Length

Alkyds General Properties