Polyester is a synthetic fiber is an important species, is the trade name of polyester fiber. It is purified terephthalic acid (PTA) or dimethyl terephthalate (DMT) and ethylene glycol (EG) as raw material by esterification or transesterification and polycondensation of prepared fiber-forming polymer - - polyethylene terephthalate fiber made by spinning and post-processing of the ester (PET).
The basic composition of the material polyester is polyethylene terephthalate, the formula [-OC-Ph-COOCH2CH2O-] n, it is also known as polyester (PET), its chemical structural formula of long-chain molecule is H (OCH2CCOCO) NOCH2CH2OH, generally relative molecular weight of about 18,000 to 25,000. In fact, where there is a small amount of monomers and oligomers exist. Low degree of polymerization of these oligomers, on a cyclic form. Polyethylene terephthalate by terephthalic acid (PTA) and ethylene glycol (EG) by direct esterification Preparation terephthalate 9BHET) after condensation from.
Polyester molecules from the point of view, it is a short-chain aliphatic hydrocarbon, an ester group, a benzene ring, terminal alcoholic hydroxyl group posed. Polyester child in addition there are two alcoholic hydroxyl end, there are no other polar groups, which polyester fibers hydrophilic poor. Polyester molecule contains about 46% ester, ester hydrolysis can occur at high temperatures, thermal cracking, the case of alkali soap solution, reducing the degree of polymerization. Polyester molecules containing aliphatic hydrocarbon chain, which enables certain polyester molecule having flex resistance, but since there is not within the polyester molecule is a benzene ring rotates, it is substantially rigid polyester macromer molecule, the molecular chains are easier to maintain linear . Thus, polyester macromolecules in this condition it is easy to form crystals, so the higher the degree of crystallinity of polyester and orientation.
Using polyester melt spinning method were observed in the microscope morphological structure having a circular cross-section and no special longitudinal structure. Under the electron microscope can be observed fibril organization filamentous,
Profiled fiber can change the elastic fiber, the fiber has a special luster and bulkiness, and to improve the performance and coverage cohesion and anti-pilling fibers and reduce static properties. Such as a triangle fibers flash effect. There are five leaf fiber fertilizer light luster, feel good, and anti-pilling. Since the internal cavity of the hollow fiber, low density, warm and good.
The thickness of the polyester chain folded lamellae applied electron diffraction measured is about 10NM, while the length of polyester single group is 1.075NM, therefore, can be considered the equivalent of a single group lamellar thickness length nine polyester molecules. However, polyester macromolecular chain length of about 1.075 * 130 (average degree of polymerization) = 140NM, shows that polyester lamellae macromolecular chain must take the folded chain structure. Folding may occur in the -CH2-CH2- segment of the chain, where the chain of the reason is better flex, easy folding.
Further, since the polyester molecules can form extended chain crystals (fibrillated crystallization). Visible, polyester internal chain folded crystallization and fibril crystallization coexist. Both crystalline fraction with the stretching ratio, heat setting conditions.