The term “paint” and “ surface coating” are often used interchangeably. Surface coating is the more general description of any material that may be applied as a thin continuous layer to a surface. Painting is distinguished from other forms of surface treatment such as electroplating, anodizing, and the lamination of the polymer film onto a surface. Paint is used to describe pigmented materials as distinct from clear films which are more properly called lacquers or varnishes.
Paint is defined as “thin coatings applied to surfaces in liquid form, which gradually dry to become gradual solids”.
The purpose of paints and surface coatings is two-fold:
These are the components that give the paint a spread able body:
-Provides the basis of continuous film, sealing or protecting the surface.
-Bind together Paint or clear finish constituents
-Convert liquid coating into solid film
-Provides liquids with adhesive properties
-Oleo: a combination of oil and resins
-It is a colorless liquid incorporated in the paint
-It is the means by which the paint may be applied
-When the liquid does not dissolve the binder, it is called a diluent
-It plays no long-term role in the paint film performance
-Recently it is very rare that a single solvent be acceptable, and so mixtures of solvents are used.
-It is avoided in a small number of compositions such as powder coatings and 100% polymerizable systems. In the polymerizable case a polymerizable monomer plays the role of solvent for the composition, being converted into polymer in the curing reaction. With powder coatings, solvents may be used in the early stages of the paint-making process, but they are removed and recycled, so do not provide a hazard or problem for the user.
N.B. In water-based systems the water may act as a true solvent for some components, but be a non-solvent for the main film former.
These are the other components that are needed for color, texture, and opacity
-These are components added to overcome possible defects in the paint
· Typical Types of defects and additives:
7. Anti-cissing: Cissing is the appearance of small, saucer-like depressions in the surface of the film
8. Anti-shriveling: Shriveling is the development of a wrinkle surface in films that dry be oxidation
9. Anti-sagging: Sagging is the development of an uneven coating as the result of excessive flow of a paint on a vertical surface
10. Anti-floating: floating is the color differences that can occur in a paint film because of the spontaneous separation of component pigments after application
11. Anti-flooding: Flooding is the permanent color change of a paint subject to shear after application. It is also called brush disturbance.
-Comprise solid particulate material which is dispersed in the binder
-Provides opacity & other optical or visual effects
-Durability (anti-corrosive): especially in primers
-Coarse particles added to achieve a wide range of purposes
-Relatively cheap particles , and for this reason may be used in conjunction with primary pigments to achieve a specific type of paint
-Provides opacity (adjunct to primary paint)
-Facilitate sanding (especially in primer surfaces)
Only Inorganic, which can be natural or synthetic
Contribution of major paint components to final paint properties
Property Film former Pigment Solvent
-R Lambourne & T A Strivens, “ Paint and surface coatings- theory and practice”, Woodhead Publishing Ltd, Abington Hall, Abington, Cambridge CB1 6AH, England:1987.
-Michael and Irene Ash, “ A Formulary of Paints and Other Coatings”,Chemical Publishing Co., Inc. New York, N.Y.:1978.
-Oil and Color Chemists’ Association, “ Surface Coatings”, Australia:1974.