There are different types of paint used in building construction.
Paint is a mechanical dispersion mixture of one or more pigments, a liquid that contains non-volatile film-forming materials, oil drying and a dilute highly volatile solvent.
When the brush is applied to the metal surface by brushing (or spraying) while the thinner evaporates, the drying oil slowly oxidizes to form a dry pigment film.
A small number of catalysts know as driers are also added to paint to accelerate the drying process of oil.
Generally, paints are used by engineers/builders for coating the surfaces of buildings and engineering materials such as iron, wood, etc.
The main purpose of applying paint are as follows:
- Paint protects iron and wood from wear and tear.
- It protects wood from different types of insects, fungus and moisture.
- It protects iron from rusting and corrosion.
- Painted surface provides smooth and beautiful appearance.
- To protect the surface from the harmful effect of atmospheric agencies.
- To give a decorative and attractive appearance to the surfaces and to make it pleasant.
Different types of paint used in building construction:
Emulsion paint is the dispersion of rubber-like resin in water.
In emulsion paints, water is used as a thinner in place of organic solvents.
Therefore emulsion has two phases, one of which is water and this paint can easily be diluted or the surface forming material (synthetic resin) is dispersed in water by a dispersing agent.
It may contain another vehicle or film-forming component such as oil, the binder can be oil pigments and extenders are dispersed in an emulsion.
Apart from these components; emulsion paints may contain emulsifying agents, stabilizers, dryers, antifoaming agents, etc.
Exterior house paints:
These paints generally have the following constituents:
Pigments, titanium dioxide, white lead, vehicles, thinners, extenders and colored pigments are also added in varying amounts.
Interior wall paints:
These paints are prepared by mixing the following constituents.
Pigments: White and coloured pigments.
Resins: Emulsified phenol-formaldehyde resins and casein.
Chemical resistant paint types:
These paints contain baked oleoresins varnish, chlorinated rubber composites bituminous varnishes and phenolic dispersers as chemical resistant materials in paint formulations.
These paints contain phosphorescent paint compositions such as pigment, vehicle and sensitizer for activation in U.V region.
These are coatings applied to metal surfaces (or bodies) for decoration and protective coating can be of the barrier type or galvanic type.
In a barrier type, a protective barrier is formed between the surface coat and its surroundings.
These paints include pigments, vehicles, anticorrosive agent, rosins (such as almonds; epoxy, polyamide, chlorinated rubbers and silicones etc.)
Alkyds resist weathering of metals, while polyamide produces tough films, resistant to chemicals, chlorinated rubbers the action of detergents and strong chemicals.
Silicones are added as heat resistant and water repellents.
Cement paint types:
Cement paints are made from a mixture of white cement, hydrated lime, pigment, very fine sand and water repellent.
These paints are available as a powder in specific color.
In such paints the dispersion medium is either water or oil, depending on the purpose of the coating.
Therefore in the case of stone masonry, brick masonry, water is used as a dispersion medium and boiled linseed is used as a dispersion medium, if the purpose is to coating the corrugated metal surfaces like iron.
For best results, a 1.5–2% aqueous solution of sodium silicate and zinc sulfate is applied as a primer coat before applying cement paint.
Constituents for various types of paint:
Pigment is a solid substance, an essential component that makes up the body of paint, it forms paint when mixed with drying oil.
Vehicle (or medium or drying oil):
These are the film-forming components of vehicle paints, they are glyceryl esters of high molecular weight fatty acids, generally present in animal and vegetable oils.
Most widely used drying oils are linseed oil, tongue oil, dehydrated castor oil and semi-drying oils are soybean oil, rosin oil, fish oil, etc.
Semi-drying oils are drying at a very slow rate, therefore they are used as a blending agent with other drying oils to obtain the desired film upon drying.
Thinners are volatile liquids that evaporate simply after application of various types of paint.
These are mixed with a suitable fixture to reduce the viscosity of the paint so that it can be easily handled and applied to the steel surface.
These are oxygen carrier catalysts, they accelerate the drying of the oil film through oxidation, polymerization and condensation.
The most effective dryers are heavy metallic soaps such as resonates, linoleates, tungstates, and naphthenates of Co, Mn, Pb, and Zn.
Cobalt materials are the most efficient and called as surface-dryers, manganese substances are completely dry, very much drying produces hard and brittle films.
Fillers (or Extenders):
The filler is inert, the white colored material has low refractive indicators which improve the properties of the paint even when there is less opacity.
Important extents used are barytes (BaSO4), talc, asbestos, gypsum, ground silica, mica, slate powder, china-clay, whiting (CaCO3), magnesium silicate (MgBOO3), CaSO4, chalk, etc.
Sometimes, plasticizers are used in paints:
- To provide elasticity and minimal cracks in the paint film.
- Common plasticizers used are tricresyl phosphate, triphenyl phosphate, tributyl phthalate, tributyl phthalate and diamyl tartrate.
- For the prevention of paint film skin, anti-skinning agents are sometimes used.
Paint is used for many purposes in building construction.
These include increasing the visual appeal, protecting the surface against weathering effects, making the surface waterproof, protecting the surface from termite attack and increasing the surface durability.