Polyester fibers, like other synthetic fiber types, are produced from polymers obtained by synthesis. The polymer substances that make up the structure of synthetic fibers are not found in nature, but are obtained from the fractional distillation of petroleum or coal. The appropriate polymer materials obtained are turned into synthetic fibers by spinning methods. The most widely used polyester fiber in the market is polyethylene terephthalate (PET) based. Polyester fiber is formed by soft spinning method from molten polymer material consisting of polyethylene terephthalate, which is a petroleum derivative.

Polyester fibers are difficult to dye. In general, these difficulties arise from the following factors:

• Since polyester fibers have high fiber crystallization, the crystalline regions are more and the amorphous regions that allow dyestuff diffusion are less.
• Absence of hydrophilic groups in their structures due to their highly hydrophobic character. Due to its high hydrophobicity, it has a very low moisture absorption rate of 0.4%.
• The absence of functional groups that can form chemical bonds with the dyestuff in the structure of polyester fibers

Due to the tight crystalline structure of polyester fibers, large-molecule dyes cannot easily penetrate. Due to its hydrophobic character, dyestuffs that bind to the fibers by electrostatic attraction forces or covalent bonds are not suitable due to the absence of functional groups to hydrophilic dyestuffs.

Disperse dyestuff, which can form chemical bonds with fibers due to its hydrophobic feature, is used in dyeing polyester, since it does not contain a chemically active group.

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