The chemistry of paint is a continuously developing science and although the ingredients have changed over the years, the four basic types of materials that make up paint are,
Solvent
Binder
Pigment
Additives
Solvent
This is the liquid that carries the solid components of paint. It must be present to allow the paint to be of correct consistency for application by brush, roller, spray or dipping.
The choice of solvent also effects the flow of the paint after it has been applied so that the film develops the correct surface appearance and so that the paint film"wets" the substrate to which it has been applied thus maximising adhesion to the substrate.
The choice of solvent also influences the initial drying properties of the paint film.
The binder, or resin component is either dissolved in liquid solvent or dispersed in non-solvent. After application the solvent evaporates to leave a solid dry film on the substrate.
The most common solvents used in architectural paints are water or mineral turps, water is used in acrylic interior and exterior paints and mineral turps is used in so called "solvent based paints" such as alkyd enamels.
A wider range of solvents are used in industrial type paints, these are generally stronger solvents and include aromatic hydrocarbons, ketones and esters.
Binder
The binder or resin is one of the most important components of paint. It is the basic solid film former that remains after the solvent has evaporated and which binds the pigment particles together into a cohesive paint film.
The binder determines many of the necessary film properties such as adhesion, gloss level, hardness, abrasion resistance, flexibility, speed of drying and durability.
In architectural solvent based paints the binder is usually an alkyd resin, in architectural water based paints the binder is usually an acrylic emulsion but some vinyl emulsions are also used.
A wider range of binders are used in industrial paints, these are usually very specialised and specific to the type of paint in which they are used. Industrial paints vary, from simple alkyd based paints for general use, to paints for cars, ships , bridges, underwater marine, tank lining, structural steel.
The more specialised binders include polyurethane resins, epoxy resins, silicone based resins, acrylic resins and inorganic silicate based resins.
Pigment
This is the component that gives paint its other most important properties of colour and opacity. The pigments used in paint are normally present as fine solid particles that are dispersed, but not soluble, in the binder and solvent.
The most common pigment used in paint is titanium dioxide and the majority of white paints use this pigment. Other inorganic coloured pigments are used such as red and yellow iron oxides, aluminium flakes and mica flakes. Zinc is used in many anti corrosion primers.
Synthetic organic pigments are used to produce very bright clean colours such as blues, greens, reds, oranges and violets.
Extender pigments are used in primers and primer surfacers to enhance film properties and o determine the filling and sanding properties of the paint film. They are also used in sealers and the like where the use of more expensive coloured pigment is not necessary.
The most common extender pigments are barium sulphate, china clay, talc and various other silica based pigments.
Additives
Additives are the specialist components of paint, they are used in small quantities to improve production and storage properties of the liquid paint product as well as application and other performance properties of the paint film.
Some typical additives that are used are,
Wetting/Dispersing agents, used to facilitate wetting of the pigment particles and dispersion of coarse aggregated pigment particles to the degree of fineness required.
Anti-settling agents, used to reduce settling of pigment particles during storage.
Anti-skinning agents, used to prevent the formation of a tough skin film on the liquid paint during storage.
Drying/Curing agents, used to improve and control the drying properties of the paint film.
Stabilisers, used to improve long term storage properties of the liquid paint.
Anti-foaming agents, used to prevent foaming of water based paints during manufacture and during application.
Anti-marring agents, these are usually silicone based compounds that are used to improve resistance to scratching and marring of the paint film.
Anti-mould agents, used to reduce mould growth on the paint film in very damp and humid environments.
Additional information on the paint industry can be found at
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