The polymeric material formed by the reaction of dicarboxylic acid (s) with glycol (s) is called polyester resin. Polyester resins are divided into two according to their chemical structure. These are classified as saturated and unsaturated. The best example of saturated polyester is PET (Polyethyleneterephthalate) material. This material melts when heated with plastic properties and can be reshaped. As unsaturated polyester resins contain carbon-carbon double bonds (C = C) in their structure, they become a hard and solid material that cannot be processed again by forming a network structure when they harden. Such materials are called "Thermoset" materials. The raw materials used in the production of polyester resin are very diverse. The choice of acids and glycols in the formulation determines the properties of the resin.