26 августа, 2015 
Pokraskin There are many ways in which oils can be classified, but in the surface coating industry, oils are mainly classified according to their film forming ability, which is primarily governed by their degree of unsaturation. Therefore, oils are classified according to their iodine value (IV) as:
• Non-drying oil: IV < 120 (for example, coconut oil, castor oil, rapeseed oil)
• Semi-drying oil: IV = 120 to 150 (for example, soybean oil, safflower oil, sunflower oil)
• Drying oil: IV > 150 (for example, linseed oil, tung oil, oticica oil).
Although non-drying oils are not suitable for film formation, they are used in the coating industry for their plasticizing effects.
Various oils used in the coating industry are listed in Table 2.2 with their respective fatty acid compositions.
Among the most important drying and semidrying oils with commercial significance for the modern coating industry are linseed oil, soybean oil, sunflower oil, dehydrated castor oil, tall oil and fish oil, while important non-drying oils are coconut oil, castor oil and palm oil. Tall oil is a misnomer; this oil is actually supplied as a mixture of fatty acids obtained as a by-product in the production of wood pulp in the paper industry.
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Table 2.2: Typical fatty acid composition of common oils used in surface coatings
a — Arachic acid and behenic acid (C20 and C21 saturated fatty acids); b — ricinoleic acid; c — rosin; d — eleostearic acid (conjugated double bond); e — licanic acid; f — mixture of conjugated and unconjugated linoleic acid; g — predominantly a mixture of arachidonic acid (C20J and clupanodonic acid (^225) with some * not a triglyceride but a mixture of fatty acids obtained as a by-product of the paper industry Note: compositions are representative; actual composition may vary from source to source |
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