Polyester fiber is a manufactured fiber composed of synthetic linear macromolecules in the chain at least 85% by mass of an ester of diol and benzene-1, 4-dicarboxylic acid (terephthalic acid). Fibers of the most common polyester, poly(ethylene terephthalate) (PET or PET), are generally made from either terephthalic acid or dimethyl terephthalate together with ethylene glycol. Dyeing of polyester fabric with disperse dyes, polyester requires the use of dispersing agents. The chemical characteristics and general application conditions of disperse dyes are characterized by the absence of solubilizing groups and low molecular weight. Dye particles have a size ranging from 0.5 to 2.0 microns, generally contain –NH2, substituted –NH2, or –OH groups in the structure, and get attached with the fiber through H-bond and van der Waals force. Dyes are retained by the fiber by physical forces. Fastness properties are very high in polyester except in certain cases. The dye-fiber (PET) affinity is the result of different types of interactions, such as hydrogen bonds, dipole-dipole interactions, and van der Waals forces.