Basics of paint coatings

Paints chemistry and application

1. Paint Coatings

2. What is Paint and Coating? Paints can be defined as a liquid, paste, or powder products which when applied on a substrate, dries to form a thin layer and serves for informative, decorative and protective purposes. Paints is a mixture (not a compound). Paint is different from DYE. The term colorant is often used for both Dyes and Pigments. i.e. substances that impart color. Dyes are chemicals /organic compounds, that are dissolved in a medium, to impart color and are absorbed into the material to which they are applied. Coating is a general term denoting a material that is applied to a surface (e.g. Paint, Varnish) Paint is pigmented, while varnish refers to clear lacquer/pigment-free coating.

3. What is Paint and Coating? A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. The purpose of applying the coating may be decorative, functional, or both. The coating itself may be an all-over coating, completely covering the substrate, or it may only cover parts of the substrate.

4. What is Paint made up of? Pigment Extender Additives Resins/Binder Solvent

5. Pigments Pigments are responsible for color, covering power and anti-corrosive properties. Pigments are finely ground crystalline solids that are dispersed/ suspended in the paint. They may be organic, in-organic and metallic. The most widely used pigment is TiO2 , due to its excellent hiding property. Other e.g. are carbon black, FeO , CdS for red, metallic salts for yellow and orange.

6. Extenders Extenders, also known as Fillers are largely finely ground crystalline solids that are dispersed in the paint, added to reduce cost of production, by replacing expensive pigments in paint. Fillers give the paint body / make the paint bulky and improves flow ( i.e. less sagging on application). They are used as matting agents (control gloss level), to provide matt or semi-gloss finishes e.g. are CaCO3, kaolin, talc, clay (Al silicates), sand, marble dust etc.

7. Additives Additives are added to modify certain properties of paint. Examples are: Driers Anti-Settling Agent Anti-Skinning Agent Defoamers Biocides Wetting and Dispersing Agents Thickeners Neutralizing Agents Co-solvent

8. Resins/Binders Binder is a polymeric substance, mostly gummy in nature. They bind components together & make it stay on the substrate. Binder is the actual film-forming component of a paint. Binders improve the paints resistance to moisture permeability, sunlight exposure, staining, cracking, damage from abrasion & adhesion to the surface. Binder/Resin may be natural or synthetic. Examples of natural resins are: linseed oil, soya beans oil, coconut oil.

9. Resins/Binders Examples of popular synthetic resins are: Alkyds, Acrylics, Epoxies, Polyurethane etc. Alkyd resins: most commonly used in solvent-based paints, e.g. gloss paints, heat cured stoving enamel paints. Poly Vinyl Acetate & Acrylic binders: are water-based binders. Epoxy resins: Epoxy resins are applied as base – coats, which prevents corrosion (tanks (fuel)and prevents friction (factory floor). Epoxy resins are also useful in marine application. Polyurethanes: Polyurethane - based paints are tough, with durable films that retain their gloss & are easy to clean. Polyurethane paints are applied as topcoats and are often used for painting aircraft. Silicon resin: are used for chiming machine (generates lots of heat) Polyester resin: used for roofing sheet.

10. Solvent Solvent is also known as CARRIER / DILUENT /THINNER  Solvents are low viscosity, volatile liquids. They dissolve the binder & hold it in suspension with the paints’ pigment. Ensures even-mixing of the paint components& makes the paint easy to apply. They are used to reduce the viscosity of paint for better flow & application. Examples of solvents are water, MEK- (methyl ethyl-ketone), MIBK- (methyl- iso -butyl-ketone), Xylene, Toluene, Butyl-acetate, Butyl-glycol, kerosene. e.t.c .