Instead of the dicarboxylic acid, it is also possible to use its corresponding dimethyl ester.Typical examples of polyesters are polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), which are used either in the form of homopolymer or in the form of copolymers.Polyethylene terephthalate is obtained from its monomers, a diol component and a dicarbox