Polyester and Vinyl Ester Coatings

olyester and vinyl ester resinbased linings are known for their solvent and chemical resistance. The different resins in these linings have broad resistance ranges, with acid resistance being a major strength. Some of the specific resins resist 1 or more chemicals or types of chemicals better than other resins, so systems often are finetuned by the choice of resin for a particular chemical environment. Esters are the reaction product of an organic acid and an alcohol. Polymers used in this class of materials are the unsaturated polyesters formed by reaction of unsaturated dibasic acids and dihydric alcohols. Styrene or a similar vinyl-type monomer is used to cross-link the resin and form the film. The polymerization is initiated by a catalyst, with the reaction by free radical addition, which is a chemical reaction mechanism unique to this class of coatings. The word “lining” in the coatings industry is commonly defined as a material used to protect the inside surface of a tank, vessel, or similar structure from highly corrosive or potentially highly corrosive exposures. Linings can be monolithic systems or built-up systems. Because of their typically thick application and use in severe chemical conditions, polyesters and vinyl esters normally are referred to as linings. They offer good adhesion to most substrates, although most applications are on steel or concrete. These linings include several systems varying in thickness, type of fillers and reinforcement, and application method. For each lining system, various polyester and vinyl ester resin bases are used to achieve the desired chemical resistance.