Contributed by BOMI International
From the February 2020 Issue
Facility managers know that maintaining the appearance of a commercial building is key. Areas that need painting or coating can significantly detract from the building’s appearance. Often, the only information given is the location of the area to be painted and the color desired. While facility managers don’t need to be experts, they should know the basics about paints, coatings, and their applications in order to make informed decisions.
The Essential Components
Paints and coatings consist of four basic components, and each of these components contributes a critical function to the paint.
Pigment provides color and helps hide and protect the surface. It also strengthens the paint film, controls gloss, screens out ultraviolet radiation (which is harmful to both the binder and the surface), and retards corrosion. Certain pigments control paint consistency and anti-settling properties to facilitate application.
Solvent is the volatile substance that dissolves or disperses the binder. Its main function is to lower the viscosity of, or thin, paint so it can be spread easily. Once the paint is applied, the solvent is expected to evaporate, leaving only the pigment and binder on the surface.
Volatility is the rate at which a solvent evaporates. Solvency is the ability of a solvent to decrease the viscosity of a paint. Do not confuse solvency, the thinning ability of a solvent, with the ability of a solvent to thin a particular paint. For example, mineral spirits is a good solvent for alkyd paints, but has a low solvency. A low solvency thinner can usually be replaced by one of higher solvency, but not vice versa. Solvency is important because a slow solvent can result in sagging, a fast solvent can cause an orange peel effect, and too much solvent can result in too thin a paint covering.
The Binder is the element that joins all the other paint components together and sticks them to the surface being painted. The binder is the liquid portion and film-forming component of the paint. By forming a continuous film, the binder encapsulates the pigment and keeps moisture and other harmful substances from penetrating the coating.
Sometimes, the binder and solvent together are referred to as the vehicle. Although a paint chemist would not approve, the terms binder, vehicle, polymer, and resin are sometimes used interchangeably.
Polymers are the major functional ingredient of the binder; they are the primary source of the paint’s physical properties and create the mechanism for cure. Resin is a term often used to refer to any material in the polymeric state. The way the liquid binder becomes a solid, or cures, upon the application of the paint depends on the nature of the polymer. There are two types of polymers: thermoplastic and thermosetting.
Thermoplastic polymers harden strictly by solvent evaporation, which means that the thermoplastic polymer is a natural film former. Thermosetting polymers must react chemically and also release solvent before a film is formed. Thermosetting polymers tend to be harder and more solvent resistant than the thermoplastic types. A disadvantage of some of the thermosetting types is the need to mix in a catalyst, which results in a short pot life. Some thermosetting polymers are catalyzed by atmospheric oxygen and water.
There are two ways in which the binder can be carried by the solvent: dissolved or suspended. When the binder is dissolved in the solvent, the paint is a solvent type. When the binder is dispersed or suspended in the solvent, usually water, the paint is called an emulsion or latex type.
Additives may be incorporated in the paint composition to enhance specific coating properties or assist in the manufacturing or application processes. Paint additives may reduce the drag of paint, improve its flow on a surface, help paint to adhere to difficult surfaces, or even improve the smell of paint.
Paints And Coatings
The information below provides a reference for understanding and selecting paints. Paints and coatings are divided into three categories:
- Architectural paints
- Commercial finishes
- Industrial coatings
Architectural paints are used for decorating and protecting homes, apartments, office buildings, and other commercial structures. They include both solvent-type and water-type paints for interior and exterior surfaces.
Commercial finishes for original equipment manufacturers (OEM) are applied to all types of manufactured products during production. These paints include the finishes on home appliances, office equipment, furniture, heating and air-conditioning equipment, automobiles, trucks, buses, railroad cars, boats, and planes. They are specially formulated to meet specific performance requirements of the products. These products require protection from a variety of harmful operating environments. Depending on the product’s design and application, the paint may be formulated to shield against weather, corrosion by fresh or salt water, chemicals, abrasion and wear, or heat and sunlight. Commercial finishes often must be colorful and attractive as well, to contribute to the sales appeal of the product.
Industrial or special-purpose coatings include maintenance coatings and paints for the transportation aftermarket. They differ from architectural coatings and commercial finishes because they are designed for special applications and to withstand unusual environmental conditions. For example, special-purpose coatings can be formulated to withstand extremities of heat and cold, to resist chemical attack in chemical plants and oil refineries, to prevent fungus in packing plants that process meat and other foods, and to withstand steam cleaning and high humidity.
The type of paint and its application should be approved by building management personnel who know and understand this process. Don’t waste money on a poor painting job. A thorough understanding of the various types of coatings and knowledge of which application should be used for the different surfaces improves the chances that your painting project will be successful.
This article is adapted from BOMI International’s Building Design and Maintenance course, part of the SMA® designation program. Visit www.BOMI.org for more information regarding this course or BOMI International’s new High-Performance Sustainable Buildings credential (BOMI-HP™).
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