Лако-красочные материалы — производство

1.1 Why paints and coatings?

Looking around, we find paints and coatings virtually everywhere. We see paint on the walls of our homes or offices, and on furniture, refrigerators, washing machines, and toasters with nice colorful finishes. Outdoors, we see cars with an increasing variety of coa­tings. Building exteriors, equipment, bridges, pipelines, superstruc­tures, and monuments are all painted with a variety of paints and coatings. If we examine them carefully, we can also find coatings on CDs and DVDs, fruits and vegetables, medical equipment such as catheters and surgical materials, reading glasses, electronic gadgets such as iPod tablets and cell phones… coatings are every­where! There are virtually limitless products that use some kind of paint or coating on their surface.

Paints and coatings are not useful products by themselves, but they make other products better, more durable, more attractive, safer, and more saleable. Paints and coatings are therefore considered enabling materials that add value to manufactured products. Think of a car without paint on it, or your nice teakwood furniture without a finish. Thin coats of paint, coating, or varnish bring life to these products and make them acceptable and durable.

In general, paints and coatings are used for three primary reasons:

• providing aesthetic appeal or decorative value to surfaces and products,

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• providing protection from damage by the external environment, and

• providing specific attributes to the product.

Many coatings satisfy more than one of the above reasons.

Satisfying an aesthetic need is a human instinct and there is much evidence indicating the use of some paints and coatings during the prehistoric era. In present times, many products must have aesthetic appeal for their acceptance and sale. Therefore, decorative value is one of the primary requirements of many paints and coatings. Since industrialization, we have been using a large quantity of metals and alloys, besides materials such as wood and masonry. After World War II, many polymeric materials, such as plastics, alloys, and composites, have been increasingly used. All of these materials, when exposed to the environment — heat, moisture, sunlight, wind, rain — are prone to degradation due to corrosion, erosion, or other forms of physical abuse reducing their service life. As a result, there has been a considerable need to protect these surfaces from environmental attack. Coatings are used as a barrier between the surfaces of such products and the environment to provide them with long-term protection.

Since there is a variety of material surfaces, such as wood, ceramic, masonry, metals, alloys, plastics, and glass, that have a wide range of physical and chemical characteristics, it is not surprising that we need a diverse range of coatings to protect them from the external environment. In addition to functioning in decoration and protection, many coatings are formulated to provide specific attributes to the product. For example, anti-microbial coatings on interior walls of hospitals control bacterial infections in addition to making buildings aesthetically appealing. The anti-fouling coatings on ship hulls keep barnacles under control, thus keeping ship surfaces clean. Without such a coating, growth of a thick layer of attached barnacles would keep increasing ship weight, leading to reduced fuel economy. A coa­ting intended for a gym floor has, apart from giving it an attractive look and having general protective value, a specific property — anti­skidding — that is essential for such applications. Thus, paints and coatings are used for many different reasons and are expected to meet the specific requirements of particular products.

While the terms paint and coating are frequently used interchan­geably, in general, the term paint is used to describe materials that have the major role of improving product aesthetics or decoration, such as interior wall paints. The term coating generally refers to materials that have a more protective role and provide long-term durability to products. In this book, the term coatings will be used most frequently to refer to both paints and coatings.