Which one among the following is commonly used as an ‘anti-skinning agent’ in paints ?
Gelatin
N-methyl pyrrolidone
Pyridine
Polyhydroxy phenol
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This question was previously asked in
UPSC NDA-2 – 2024
‘Skinning’ in paints refers to the formation of a solid or semi-solid film on the surface of the liquid paint when exposed to air. This is primarily due to the oxidation and subsequent polymerization of the drying oils or alkyd resins used as binders, catalyzed by metal driers. Anti-skinning agents are added to paints to prevent this surface oxidation and polymerization. Many anti-skinning agents are volatile antioxidants or complexing agents that temporarily deactivate the metal driers. Phenolic compounds, particularly polyhydroxy phenols and hindered phenols, are effective antioxidants that can scavenge free radicals and prevent the oxidation chain reactions that lead to skinning. Oximes (like methyl ethyl ketoxime) are also commonly used as anti-skinning agents by complexing with metal driers. Polyhydroxy phenol represents a class of compounds known for their antioxidant properties, making them suitable for use as anti-skinning agents.