Polyester fiber丨What are the differences between PET, PBT and PTT?

Synthetic fiber Different from natural fibers, they have unique properties based on different molecular compositions, such as high strength, light weight, easy to wash and quick-drying, good elasticity, and not afraid of mildew, etc. Currently, their application in the textile field is gradually surpassing that of natural fibers.

Polyester fiber, as a major category of synthetic fibers, has been successfully developed since 1941 Later, it gained favor from all walks of life and developed rapidly. In recent years, its market share has gradually surpassed polyamide fiber and become the largest variety of synthetic fiber.

There are many varieties of polyester fiber, which are given in GB/T4146.1-2009 Three types have been developed, namely polyethylene terephthalate (PET) fiber, polybutylene terephthalate (PBT) fiber and polytrimethylene terephthalate (PTT) fiber.

Among them, the trade name of PET fiber in my country is polyester, and polyester is just polyester A type of fiber. Due to its easy availability of raw materials and excellent performance, polyester has become the fiber with the largest output and the most widely used among chemical fibers. It is precisely because of this that people mistakenly think that polyester fiber is polyester. However, in recent years, with the With the improvement of fiber production technology, polyester fiber has added two new members, PBT and PTT. With the emergence of PTT fiber and PBT fiber, polyester fiber is no longer exclusive to polyester. However, in actual detection, since these three types of fibers are difficult to distinguish through ordinary methods, theoretically, they can be identified through a combination of infrared spectroscopy and melting point methods, but there are also difficulties in the identification process. Therefore, according to the standard GB/T 4146.1-2009, a “polyester fiber” report will generally be issued, only if the client explicitly requests it and the sample can be determined to be “polyethylene terephthalate (PET)” , only the testing agency can classify it as “polyester”.

PET, PBT and PTT fibers are all polyester fibers, but their properties are different differences, so the application fields of these three fibers are not exactly the same.

PET fiber

PET fiber, also known as polyethylene terephthalate fiber, is often called polyester in my country . At present, PET fiber is mainly produced by the direct esterification method of terephthalic acid (PTA) and ethylene glycol (EG) or the transesterification method of dimethyl terephthalate (DMT) and ethylene glycol (EG). .

The longitudinal section of PET fiber is similar to that of PTT fiber, and the horizontal section under the microscope The cross-section is circular, the longitudinal thickness is relatively uniform, there is less hairiness, and the surface is smooth. The molecular formula of PET fiber is [-OC-Ph-COOCH2CH2O-]n. The single group is composed of a benzene ring, two ester groups and two methylene groups. Composition. Due to the presence of benzene rings in the PET molecule, it needs to be stretched after traditional melt spinning, so that it can crystallize quickly, which can make the fiber produced with higher orientation and crystallinity. PET fiber has high strength, good elasticity, excellent heat setting performance, good heat resistance, acid and alkali resistance, etc.

Polyester is widely used in clothing, decoration and industrial fields due to its simple processing and low price. In the field of clothing, fabrics made of PET are easy to wash and dry quickly, and have the title of “washable and wearable”, and their The ester bonds in the molecule have strong antioxidant capabilities and are not easily destroyed by products such as detergents and soaps. At the same time, PET fibers are not easily eroded by microorganisms, so the fabric has good durability. After heat setting, polyester fabric has stable size and shape, good stiffness and is not easy to shrink. It can be used to make shirts, men’s suit pants, outerwear and jackets, etc. The shortcomings of polyester are mainly due to the tight molecular arrangement and lack of hydrophilic groups, so it has poor dyeability, hygroscopicity, and antistatic properties, and the product is easy to burn.

With the development of science and technology and people’s pursuit of high-quality clothing, PET fiber Multifunctional applications are a research direction at this stage. In order to improve the shortcomings of poor hygroscopicity and easy generation of static electricity in polyester fiber, Li Fang used nano-TiO2 to modify the surface of polyester fiber. While improving the defects of polyester itself, the addition of TiO2 gave it antibacterial, anti-ultraviolet, photocatalytic self-cleaning, etc. Characteristics; Shi Zheng developed antibacterial PET fibers using chemical modification methods such as metal ions and organic acids; Sun Pengxiao studied the surface modification and weaving methods of PET fibers used in medical artificial ligament materials.

PBT fiber

Polybutylene terephthalate (PBT), abbreviated as polybutylene terephthalate (PBT), is formed by the esterification and polycondensation of dimethyl terephthalate (DMT) or terephthalic acid (TPA) and butylene glycol. Since PBT fiber is rich in raw materials and its 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 the larger methylene molecule of PBT is spiral, which is similar to the nylon molecular structure, while methine The base chain segment is longer than PET, so the softness, wear resistance and elasticity of PBT fiber are similar to nylon, and its chemical properties are similar to PET fiber. Because the molecules of PBT fiber can move freely, PBT fiber has excellent tensile and compression elasticity and wrinkle resistance. Compared with the poor dyeability of PET, the glass transition temperature of PBT is only 22°C. It can be boiled and dyed with disperse dyes at normal pressure without a carrier. However, due to the existence of type a and type B crystal deformation, PBT is susceptible to high temperature at high temperatures. Lower dimensional stability is poor.

Due to the excellent resilience, mildew and mothproofing, and good curl elasticity of PBT fiber , antistatic and dyeability, PBT fiber has a large number of applications in elastic clothing such as swimsuits, sportswear, ski suits, jumpsuits, dance tights, etc. Spandex is more expensive and has poor light resistance and is prone to yellowing. However, the elasticity of PBT fiber is second only to spandex and better than nylon. It can completely replace spandex in some fabrics. For example, in stretch jeans, spandex is usually used as elastic.However, the strength of spandex is low and it is easy to break after long-term wear and friction. Using PBT fiber instead of spandex as the elastic yarn can effectively improve this situation. Because PBT fiber has a wool-like feel, it can be interwoven with cotton, linen, etc. in the wool spinning industry for autumn and winter clothing. It is also an ideal imitation down and filling material.

In addition to being used alone as a textile material, PBT fiber has been used in modified applications in recent years. It has also been researched and developed in many aspects. For example, PBT/PET composite spinning fiber not only has good spinnability, but also has a soft hand feel, high fluffiness, and is easy to dye. It can be used as a wool-like fiber and can also replace spandex. At this stage, the elasticity of PBT block copolymer fiber can reach 80% of spandex. %, and other properties are better than spandex. At the same time, this fiber looks like silk and can be interwoven with silk to form special style fabrics.

PTT fiber

PTT fiber (polytrimethylene terephthalate) is a new type of polyester fiber developed by Shell Company in the mid-1990s. PTT can be made by melt polycondensation of 1,3-propanediol (PDO) and dimethyl terephthalate (DMT) after transesterification, or by melt polycondensation of PDO and terephthalic acid (PTA). PTT fiber has a smooth surface and is a semi-crystalline thermoplastic polyester. It is different from PBT fiber and PET fiber in that the chemical structure of PTT fiber has a trans-para-para-trans conformation with the lowest energy and thus presents an obvious “Z” shaped conformation. There are two methylene units on the molecular links of PET and PBT, while there are three methylene units on the molecular chain links of PTT, so there will be an “odd carbon effect” between the molecular chains. This molecular structure makes PTT fiber It has the same deformation ability as a coil spring and has better resilience than PET and PBT. As a new type of synthetic fiber, polytrimethylene terephthalate (PTT) fiber has excellent dimensional stability, stain resistance, wrinkle resistance, abrasion resistance and easy dyeing, coupled with its unique molecular chain structure. The high resilience brought by it is called the “21st century new polyester fiber”.

PTT fiber, as a new material, has the advantages of PET fiber and PBT fiber but also overcomes the some of their shortcomings.

Most swimwear on the market currently uses nylon fabrics, and nylon has good lightfastness and durability. The low chlorine resistance limits the application of nylon swimsuits. Comparing the elasticity of nylon and PET, it was found that the elasticity of PTT fabric is better than that of PET and nylon, and can meet the needs of swimwear elasticity, size adaptability and pressure comfort. At the same time, PTT fabric is easy to dye, has high color fastness and is chlorine resistant. The characteristics of good sex and UV resistance make PTT fiber an ideal swimsuit material. The PTT/wool blended fabric can not only solve the problem of wool yield, but also has a rich hand feel, excellent drape performance, and has the multiple properties of nylon and spandex. In view of the easy plasticity of PTT fabrics and the easy recovery of wrinkles, the application of PTT fibers as shape memory fabrics is also constantly developing. PTT fiber nonwovens can be used in carpet backing, artificial leather, protective materials and medical applications. At the same time, because of their soft feel and good drape, they have great potential in women’s sanitary napkins and disposable diapers.

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 multi-functional, composite Chemical new fibers are the direction of future efforts. As a synthetic fiber, the efficient, low-carbon and environmentally friendly production of fiber is the key to process improvement, and the recycling and reuse of fabrics also has potential market value.