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.