Surface Coatings Including Paints

The principal components in a paint are pigment, binder and solvent. The basic steps in the manufacture of paints are as follows [33]  

Most coatings are applied as solutions, emulsions or suspensions ofthe pigment, and are converted to solid films after application, usually by allowing the solvent to evaporate. Latex, one of the simplest of paint formulations, is simply a dispersion of high molar mass polymer particles in water. In the first stage of solvent evaporation, the rate of evaporation is essentially independent of the presence of the dissolved or dispersed pigment. As solvent evaporates, the viscosity increases and the free volume decreases, so that the rate of evaporation becomes dependent on how rapidly solvent molecules can diffuse to the surface of the film [35]. 

In organic systems, wetting and dispersion of the pigments is usually quite easy but stabilization of the dispersions normally requires steric stabilization. 

Paints may also need to contain antifoaming and/or defoaming components as air can become incorporated into a paint during any or all of dispersing, transportation, mixing, filling and application steps [33,37]. Hydrophobic components, such as treated (hydrophobic) silicas or waxes, maybe added to water-based paints in accordance with the principles described in Section 7.2.2, although there is a tendency to use quite specific antifoams for specific paints [33]. 

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Thin films of organic compounds are often applied from solvents. These films include adhesives, coatings for magnetic tapes, inks, paints, and varnishes. Over 11% of all products have some kind of coating. Worldwide sales of coating-based products are over 5 trillion dollars.285 A number of reviews of surface coatings and paints are available.286 Several other reviews cover ways to minimize the use of solvents in these.287 Much of the discussion that follows is taken from these latter reviews. 

To state the means by which the required life of the coating is to be achieved. This includes surface-preparation standards, paints and systems, application, storage, handling and transport, quality control ... 

The processes are dealt with fully in Chapters 11, 14 and 15. Because many paint systems include an initial surface pretreatment, e.g. chromated aluminium or phosphated steel, BS4479 1990, Part 3 deals with conversion coatings and should be consulted by designers. Whatever the method of treatment, liquids must be able to drain quickly and freely from the surfaces. Crevices where liquids can become entrapped are best avoided. The surface configuration needs to be such that active solutions can be washed away, leaving the surface to be painted completely free from unreacted pretreatment solution. Failure to achieve the requisite level of freedom from the surplus chemicals causes paint failure, e.g. osmotic blistering. 

Protecting a surface from corrosion by coating can be accomplished by a number of well-established processes which include paints, metal plating (with zinc or cadmium), diffusion, thermal spraying, and, more recently, vapor deposition processes. Of these physical vapor deposition (PVD) is used extensively in corrosion protection. Typical applications are ... 

Coatings are applied to the outside or inside of the foundation, creating a radon-resistant barrier between the source and the inside of the home. They come in a wide variety of materials including paint-like products that can be brushed on the interior of the foundation, tar-like materials that are applied to the outside, and cementitious materials that can be brushed or troweled on. They cannot be applied to the underside of the concrete floor slab for obvious reasons, so they must be applied to the inside surface of the slab. The effective life of an interior coating can be greatly diminished by damage therefore, care must be taken to provide protection to the material used. 

Together, antifreeze, PET, and polyester polymers account for about 98% of the ethylene glycol produced in the United States. It is also used sometimes as a deicer for aircraft surfaces. The two hydroxyl groups in the EG molecule also make EG suitable for the manufacture of surfactants and in latex paints. Other applications include hydraulic brake fluid, the manufacture of alkyd resins for surface coatings, and stabilizers for water dispersions of urea-formaldehyde and melamine-formaldehyde The hygroscopic properties (absorbs moisture from the air) make EG useful as a humectant for textile fibers, paper, leather, and adhesives treatment. 

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