TABLE OF CONTENTS Oils (Martens, 1974) are used in coatings either by themselves, as a portion of the nonvolatile vehicle, or as an integral part of a varnish, when combined with resin, or of a synthetic liquid, when combined with the resinous portion of the synthetic.
Oil improves the flexibility of the paint film: eliminating oil from certain formulations would cause the film to crack.
In exterior finishes, oil gives durability.
As part of the nonvolatile vehicle, oil improves gloss.
Some oils give moderate resistance to water, soap, chemicals, and other corrosive products.
Some oils give specialty properties such as wrinkling (for wrinkle finishes).
With special treatments, oils can be used to improve leveling and the flow, nonpenetration, and wetting properties of the vehicle. They also have other desirable characteristics.
Most of the oils are triglycerides of fatty acids. Glycerin, C 3H 5(OH) 3, has three OH groups, each of which can react with the carboxyl group of a fatty acid. Such a reaction will result in water being split off and a triglyceride being formed. This is the oil as it is found in nature.
The properties of the specific oil depend largely on the type of fatty acids in the oil molecule. Thus, highly unsaturated fatty acids will give improved drying properties but have a greater tendency toward yellowing. Drying is especially improved if the double bonds are in a conjugate system in which two double bonds are separated by a single...
