Not All Polyester Fibers Are Called Polyester

Date:Sep 30, 2019

Polyester generally refers to a polymer compound obtained by polycondensation of a dibasic acid and a diol, and the basic chain links are linked by an ester bond. There are many varieties of polyester fiber, such as polyethylene terephthalate (PET) fiber, polybutylene terephthalate (PBT) fiber, and polypropylene terephthalate. , PPT) fiber, etc., in which the content of polyethylene terephthalate is more than 85% of the fiber, the molecular weight is generally controlled between 18000 ~ 25000, the main molecular structure is as follows:

Cationic dye-dyeable polyester (CDP) fiber

Modified polyester (CDP) dyeable with cationic dyes can be prepared by introducing an acidic group capable of binding a cationic dye into the PET molecular chain. CDP was first developed by DuPont of the United States. At the end of the 20th century, its output accounted for 1/6 of the total output of PET fiber. Its typical varieties are Dacron T64 and Dacron T65. CDP not only has good dyeing performance, but also can be dyed in the same bath as natural fibers such as wool, which is convenient for the dyeing fabric to simplify the dyeing process. If it is blended with ordinary polyester, it can also produce the same bath color effect, which greatly enriches the color of the fabric. Therefore, CDP has become a fast-growing variety of modified polyester. The preparation of CDP is mainly to add a third monomer or a fourth monomer, such as sodium dimethyl isophthalate (SIPM), to the PET macromolecular chain by copolymerization, graft copolymerization or the like. Since a negatively charged sulfonic acid group is added to the CDP molecular chain, when the metal ion on the sulfonic acid group is exchanged with the cation in the dye, the dye ion is immobilized on the macromolecular chain of the CDP. The salt formed by the dyeing is continuously removed in the aqueous solution, and the reaction is continuously carried out to finally achieve the dyeing effect.

The production process of CDP is similar to that of PET. It has continuous and intermittent points, and can be divided into DMT route and PTA route due to different raw material sources. Since CDP adds a new group to the macromolecular chain, the original structure of the fiber is destroyed, and the melting point, glass transition temperature, and crystallinity of the fiber are lowered. In the amorphous region, the intermolecular voids increase, which facilitates the penetration of dye molecules into the interior of the fiber. CDP has a lower strength than ordinary polyester, but it improves the anti-pilling performance of the fabric, making the hand feel soft and full, and can produce high-grade imitation wool products. The dyeing of ordinary CDP still needs high temperature (120~140 °C) high pressure or under the condition of adding carrier, so that it can have better dyeability. Therefore, when selecting dyes, it must be noted that the selected dyes should have better heat stability. Sex.