The main raw material is polyester, The basic composition of polyester is polyethylene terephthalate, so it is also called polyester fiber (PET). In fact, there are also small amounts of monomers and oligomers present. These oligomers have a low degree of polymerization and exist in a cyclic form. Polyethylene terephthalate can be obtained by polycondensation of terephthalic acid (PTA) and ethylene glycol (EG) by direct esterification to obtain ethylene terephthalate (9BHET). From the perspective of the molecular composition of polyester, it is composed of short aliphatic hydrocarbon chains, ester groups, benzene rings, and terminal alcohol hydroxyl groups. Except for two terminal alcohol hydroxyl groups, there are no other polar groups in the polyester molecule, so the hydrophilicity of polyester fiber is extremely poor. Polyester molecules contain about 46% ester groups, which can be hydrolyzed and thermally cracked at high temperature, and saponified in case of alkali, which reduces the degree of polymerization; polyester molecules also contain aliphatic hydrocarbon chains, which can make polyester molecules have a certain Flexible, but due to the benzene ring that cannot be rotated internally in the polyester molecule, the polyester macromolecule is basically a rigid molecule, and the molecular chain is easy to maintain a linear shape. Therefore, polyester macromolecules are easy to form crystals under this condition, so the crystallinity and orientation of polyester are high.