MAJOR TYPES OF PROTECTIVE COATINGS

摘要

Alkyds are produced by reacting synthetic oils and certain resins which gives a paint which dries by oxidation and has widespread use in the coatings industry. Alkyds are easy to apply, can be applied to a range of surface preparation standards, are easily maintained, come in a variety of colours, have reasonable durability and are generally cheap. As a result of these advantages, they provide good economy in a range of mild to moderate environments. They are not suitable in continuously wet or very damp conditions and provide only fair resistance to acids, alkalis and solvents. Alkyds can be modified with a range of other resins which can improve properties by taking on some of the qualities of the modifier. For example, silicone alkyds have better weather resistance and particularly resistance to high temperatures. Vinyl alkyds have much improved water resistance, along with better adhesion and general weather durability. Urethane alkyds have greatly improved abrasion resistance. When epoxy resin is reacted with one of the alkyd resins it forms what are known as epoxy esters. These provide a hard, more chemically resistant coating which, like epoxies, tends to chalk so epoxy esters are generally used as primers or for interior use. While improving the properties, modification naturally adds to the cost.