PAINT COMPONENTS 1-5 2. RESINS Resins, together with pigments, are main components of coating. Generally, a resin is a viscous and transparent liquid which is applied over an object and forms a coat when dried. Properties of resins have direct effects on finish of the paint (texture, luster, etc.), workability (drying time), and performance of the coat (hardness, resistance against solvent, weathering, etc.). Resins that are used in paints are generally divided into the following types: (1) NATURAL RESINS Natural resins are extracted mainly from plants, and are used to make varnishes, lacquers, etc. They are not used with industrial products that require large volumes of natural resins.
II NATURAL RESINS --~~- I (2) SYNTHETIC RESINS This type of resins are the results of the chemical reactions of various chemicals, and most modern paints are made mainly from synthetic resins. Synthetic resins are further divided into thermoplastic resins and thermosetting resins. SYNTHETIC RESINS CD Thermoplastic resins Thermoplastic resins can be softened repeatedly by heating and hardened again on cooling. Most of them are highly flexible, and are dissolved by solvents. Typically, they include such materials as nitrocellulose, cellulose acetate butyrate, polypropylene and nylon.
® Thermosetting resins Thermosetting resins are initially soft but change irreversibly to a hard rigid form when heated. They are generally very hard but brittle, and resistant against solvents. Typically, they include amino resins, polyurethane resins and epoxy resins. -7-