Synthetic fiber is different from natural fiber. According to the different molecular composition, synthetic fiber has unique properties, such as high strength, light weight, easy washing and quick drying, good elasticity, no mildew and moth, etc. at present, its application in the textile field is gradually surpassing that of natural fiber. Polyester fiber, as a large category of synthetic fiber, has been favored by all walks of life and developed rapidly since its successful development in 1941. In recent years, its market share has gradually exceeded polyamide fiber and become the largest variety of synthetic fiber. Although pet, PBT and PTT fibers belong to polyester fibers, their properties are different, so the application fields of these three fibers are not exactly the same.
01 PET fiber PET fiber, also known as polyethylene terephthalate fiber, is often called polyester in China. At present, PET fiber is mainly prepared by direct esterification of terephthalic acid (PTA) and ethylene glycol (eg) or transesterification of dimethyl terephthalate (DMT) and ethylene glycol (eg).
The longitudinal section of PET fiber is similar to that of PTT fiber. Under the microscope, the cross section is circular, the longitudinal thickness is uniform, the hairiness is few, and the surface is smooth. The molecular formula of PET fiber is [- oc-ph-cooch2ch2o -] n, and the single group is composed of one benzene ring, two ester groups and two methylene groups. Due to the benzene ring in pet molecule, it needs to be stretched after traditional melt spinning to make it crystallize rapidly. In this way, the fiber orientation and crystallinity can be higher. The PET fiber produced from this has the properties of high strength, good elasticity, excellent heat setting performance, good heat resistance, acid and alkali resistance.
Polyester is widely used in clothing, decoration and industrial fields because of its simple processing and low price. In the field of clothing, the fabric made of pet is easy to wash and dry, with the title of "washable and wearable", and the ester bond in its molecule has strong antioxidant ability, which is not easy to be damaged by detergent, soap and other products. At the same time, PET fiber is not easy to be eroded by microorganisms, so the fabric has good wear resistance. After heat setting, polyester fabric has stable size and shape, good straightness and not easy to shrink. It can be used to make shirts, men's suit pants, coats and jackets. The disadvantages of polyester are mainly due to the close arrangement of molecules and the lack of hydrophilic group, so the dyeability, hygroscopicity and antistatic property are poor, and the product is easy to burn.
With the development of science and technology and people's pursuit of high-quality clothing, the multifunctional application of PET fiber is a research direction at this stage. In order to improve the disadvantages of poor hygroscopicity and easy to generate static electricity of polyester fiber, Li Fang modified the surface of polyester fiber with nano-TiO2. While improving the defects of polyester fiber, the addition of TiO2 gives it the characteristics of antibacterial, UV resistance, photocatalytic self-cleaning and so on; Shi Zheng developed antibacterial PET fiber by chemical modification methods such as metal ions and organic acids; Sun pengxiao studied the surface modification and weaving method of PET fiber applied to medical artificial ligament materials.
02 PBT fiber
Polybutylene terephthalate (PBT) is a polycondensation of dimethyl terephthalate (DMT) or terephthalic acid (TPA) and butanediol after esterification. Because PBT fiber is rich in raw materials and the production process is similar to polyester, it has been produced on a large scale in recent years. The molecular formula of PBT is [(CH2) 4oocc6h4coo] n, which has two more methylene chains than pet molecules, and the main chain structure of methylene molecules with larger PBT is helical, which is similar to nylon molecular structure, while the methylene chain segment is longer than pet. Therefore, the softness, wear resistance and elasticity of PBT fiber are similar to those of nylon fiber, and its chemical properties are similar to those of PET fiber. Because the molecules of PBT fiber can move freely, PBT fiber has excellent tensile and compressive elasticity and wrinkle resistance. Compared with pet, the glass transition temperature of PBT is only 22 ℃, which can be boiled with disperse dyes under normal pressure without carrier. However, PBT has poor dimensional stability at high temperature due to type A and type B crystal deformation.
Due to the excellent resilience, mildew and moth resistance, good crimp elasticity, antistatic and dyeability of PBT fiber, PBT fiber is widely used in elastic clothing such as swimsuit, sportswear, ski suit, jumpsuit, Dance Tights and so on. Spandex is expensive and has poor light resistance, which is prone to yellowing. The elasticity of PBT fiber is second only to spandex and better than nylon. It can completely replace spandex in some fabrics. For example, spandex is usually used as elastic yarn in elastic jeans, but the strength of spandex is low and it is easy to break after wearing and friction for a long time, This situation can be effectively improved by using PBT fiber instead of spandex as elastic yarn. Because PBT fiber has a feel similar to wool, it can be interwoven with cotton and hemp in the wool textile industry as autumn and winter clothes. At the same time, it is also an ideal imitation down and filling material.
In addition to being used as textile materials alone, PBT fiber has also been studied and developed in many aspects in recent years. For example, PBT / PET composite spinning fiber not only has good spinnability, but also the fabric feels soft, high fluffy and easy to dye. It can not only be used as wool like fiber, but also replace spandex; At present, the elasticity of PBT block copolymer fiber can reach 80% of spandex, while other properties are better than spandex. At the same time, the appearance of this fiber is similar to real silk and can be interwoven with real silk into special style fabrics.
03. PTT fiber PTT fiber (polyethylene terephthalate) is a new polyester fiber developed by shell in the mid-1990s. PTT can be formed by melt polycondensation of 1,3-propylene glycol (PDO) and dimethyl terephthalate (DMT) after transesterification, or by melt polycondensation of PDO and terephthalic acid (PTA). The surface of PTT fiber is smooth and smooth. It is a semi crystalline thermoplastic polyester. It is different from PBT fiber and PET fiber in that in the chemical structure of PTT fiber, there is a trans paraffinic paraffinic trans conformation with the lowest energy, which presents an obvious "Z" conformation. Therefore, there will be "odd carbon effect" between molecular chains. This molecular structure makes PTT fiber have the same deformation ability as coil spring, and the resilience is better than pet and PBT. As a new type of synthetic fiber, polyethylene terephthalate (PTT) fiber is called "new polyester fiber in the 21st century" because of its excellent dimensional stability, stain resistance, wrinkle resistance, wear resistance and easy dyeing, as well as the high resilience brought by the unique molecular chain structure.
As a new material, PTT fiber not only has the advantages of PET fiber and PBT fiber, but also overcomes some of their shortcomings.
At present, most swimsuits on the market use nylon fabric, and the low light resistance and chlorine resistance of nylon limit the application of nylon swimsuit. By comparing the elasticity of nylon and pet, it is found that the elasticity of PTT fabric is better than that of pet and nylon, which can meet the needs of swimsuit elasticity, size adaptability and pressure comfort. At the same time, the characteristics of PTT fabric such as easy dyeing, high color fastness, good chlorine resistance and UV resistance make PTT fiber an ideal swimsuit material. PTT / wool blended fabric can not only solve the problem of wool output, but also have rich hand feel, excellent drapability and multiple properties of nylon and spandex. In view of the easy plasticity of PTT fabric modeling and the easy recovery of folds, the application of PTT fiber as shape memory fabric is also developing. PTT Fiber Nonwovens can be used in carpet backing, artificial leather, protective materials and medical treatment. At the same time, because of its soft feel and good drapability, it has great potential in women's sanitary napkins and disposable diapers.
Epilogue PBT, pet and PTT fibers have broad prospects in the textile field. With the development of science and technology and the improvement of people's requirements for clothing comfort and versatility, the development of multifunctional and composite new fibers is the direction of efforts in the future. As a synthetic fiber, the production of fiber with high efficiency, low carbon and environmental protection is the key to process improvement, and the recycling of fabric also has potential market value.
