XII Chemistry BIEK Topic - Paints (Short Note)

Paints (Short Note)
Definition
Paints are fluids that are applied on a surface to form a hard continuous film on it for protection or decoration.

Wooden and metallic articles are coated with paints to decorate them as well as to protect from corrosion or rusting.




Composition of Paints
Paints are usually composed of three components.

1. Pigments

2. Binders

3. Volatile Solvent

To make a paint, a suitable solvent is used in which both the binder and the pigment are dissolved.


1. Pigments

The pigment of paint gives it colour, it also gives hardness and bulk. Common pigments are titanium dioxide - TiO2 (white), Iron oxide - Fe2O3 (brown or red), Carbon Black - C (black), Chrome Yellow - PbCrO4 (yellow) and organic dyes of various colours.


2. Binders

The binder or vehicle is the part of the paint that carries the pigment particles and hold the entire film of the paint on the surface. Generally some plant oils such as linseed oil, natural and synthetic resin (liquid plastics) are used as binders.


3. Volatile Solvents

To make paint a suitable solvent is selected in which both the pigment and binder are dissolved. The solvent evaporates after the paint is applied. Solvent does not effect the quality of dry paint. Commonly, water or turpentine is used as solvent.

Classification of Paints
On the basis of nature of solvent, the paints are classified into the following two classes.

1. Oil Based Paints

2. Water Based Paints


1. Oil Based Paints

In these paints turpentine is used as solvent. Turpentine is a liquid mixture of hydrocarbon that is obtained from pine trees.


2. Water Based Paints

In these paints, water is used as solvent. Both binders and pigments form a suspension in water.