Engineering Chemistry S Datta

PAINTS 477
Lacquers
Lacquers are dispersion or solution of a film forming material (like-nitrocellulose), resins
and plasticizers in solvents and or diluents. The purpose of using of a lacquer is for protective
and decorative aspects. The lacquer dries from the surface on which it is applied by simple
evaporation of the volatile constituents, i.e., solvents.
The table given below displays the constituents of lacquers:
Class Materials Functions
1. Film forming (i) Cellulose derivative:
(i) Nitro cellulose
(ii) Cellulose acetate
(ii) Resins and gums:
(i) Ester gum
(ii) Copal
(iii) Synthetic resins:
(i) Phenol aldehyde
(ii) Alkyd
For waterproofness and durability; To
improve retention of glass, adhesion
and water resistance
2. Pigments — For pleasing colours
(Not added in
clear lacquers)
3. Solvents (i) Esters:
(i) Ethyl acetate
To dissolve film forming materials
(ii) Butyl acetate
(iii) Amyl acetate
(ii) Ketones:
(i) Methyl ethyl ketone (MEK)
(ii) Cyclohexanone
(iii) Alcohols:
(i) Ethyl alcohol
(ii) Butanol
(iii) Amyl alcohol
4. Diluents (i) Coal tar products:
(i) Toluene
(ii) Benzene
(iii) Solvent naphtha
5. Plasticizers (i) Castor oil
(ii) Dibutyl phthalate
(iii) Tricresyl phosphate
To reduce viscosity and cost
To reduce film brittleness and to
improve adherence
Enamels and Japans
Pigmented varnishes or lacquers are known as enamels. Japans are closely related to
enamels. Carbon black is added in deep black Japans.
Enamels are brushed or sprayed on the surface and finally hardened by baking. The
deep black Japans are based on boiled linseed oil and are made by cooking linseed oil with