spandex (PU) fiber
spandex fiber (referred to as PU fiber) belongs to the polyurethane type structure, with high elongation, low elastic modulus and high elastic recovery rate. In addition, spandex also has excellent chemical stability and thermal stability. It is more resistant to chemical degradation than latex silk , and the softening temperature is about 200℃ or above. Spandex fiber is sweat resistant, seawater resistant and resistant to various dry cleaning agents and most sunscreen oils. Long-term exposure to sunlight or in chlorine bleach can also fade, but the degree of fading varies greatly depending on the type of spandex. Clothing made of spandex-containing fabrics has good shape protection, stable size, no pressure, and comfortable to wear. Usually, just add 2% to 10% spandex to make the underwear soft, close-fitting, comfortable and beautiful, making the sportswear soft and move freely, making fashion and casual wear good drape, shape-resistance and fashion. Therefore, spandex is an essential fiber for the development of highly elastic textiles.
polypropylene glycol terephthalate (PTT) fiber
polypropylene glycol terephthalate fiber (PTT fiber for short) is a new product in the polyester family. It belongs to polyester fiber and is a common product of polyester PET. PTT fiber combines the characteristics of polyester and nylon, has soft feel and good elastic recovery. It is easy to dye under normal pressure, has bright colors, and has good dimensional stability of fabrics. It is very suitable for the field of clothing. PTT fibers can be blended, twisted, and interwoven with natural fibers such as wool and cotton or synthetic fibers, and can be used in woven fabrics and knitted products. In addition, PTT fiber can also be used in industrial fabrics and other fields, such as manufacturing carpets, decorations, webbing, etc. PTT fiber has the advantages of spandex elastic fabrics, and is a new type of fiber with a promising development price.
elastic fiber T-400
T-400 fiber is a new type of elastic fiber product developed by DuPont to address the certain restrictions on spandex fiber in textile applications. T-400 does not belong to the spandex family. It is made of two polymers, PTTh and PET, with different shrinkage rates, and is a parallel composite fiber. It solves many problems such as spandex's difficulty in dyeing, excessive elasticity, complex weaving, unstable fabric size and aging of spandex during use.
The fabric made of it has the following characteristics:
(1) Easy elasticity, comfortable and long-lasting;
(2) The fabric is soft, crisp and drape;
(3) The fabric is flat and has good wrinkle resistance;
(4) It absorbs moisture and is quick to dry, and has a smooth feel;
(5) Good dimensional stability and is easy to handle.
T-400 can be blended with natural fibers and artificial fibers to improve strength and softness. The blended fabric has a clean and smooth appearance and the outline of the clothing is clear. The clothes can still maintain a good appearance after repeated washing. The fabric has good color fastness and is not easy to fade. It is still like a new clothes when worn for a long time. At present, due to its excellent consuming performance, T-400 is widely used in pants, denim, sportswear, high-end women's clothing and other fields.
PU, PTT and T-400 Fiber Identification Method
Combustion method uses the differences in the combustion characteristics generated by different chemical compositions of various fibers to identify the types of fibers. The method is to take a small bunch of fiber samples to burn and carefully observe the fiber combustion characteristics and the shape, color, softness and hardness of the residue, and smell the odor it produces.
From the combustion characteristics of the above three elastic fibers, we can easily distinguish PU from the other two fibers based on the situation after the three fibers leave the flame. In addition, the odor and residue characteristics of these three fibers are significantly different when burning, which can be identified.
microscope method is to use a microscope to observe the longitudinal and transverse cross-sectional morphology of the fibers. According to the morphological characteristics of the fibers, the fibers are identified by the standard microscope photos and standard data. The chlorine-containing nitrogen-containing color reaction method is to identify whether the fibers contain chlorine and nitrogen elements based on the flame and acid-base method. During the test, take the clean copper wire , remove the oxide layer on the surface with fine sandpaper, burn the copper wire red in the flame and contact the sample immediately, and then move the copper wire into the flame. If the flame is green, it means that the fiber contains chlorine. Put a small amount of chopped fiber into the test tube and cover it with an appropriate amount of sodium carbonate , heat the test tube on the alcohol lamp , put a red litmus test paper on the test tube mouth. If the litmus test paper turns blue, it means that the fiber contains nitrogen. It can be seen from Table 3 that we can easily identify PU fibers by chlorine-containing nitrogen-containing color method, but we cannot distinguish between PTT and T-400 fibers.
dissolution method is to identify fibers based on the different chemical composition of various fibers and different dissolution properties in different chemical reagents . During the test, a small amount of fiber can be taken to the test tube, and a certain reagent (the ratio of sample to reagent is 1:50) can be injected, and its solubility performance can be observed under certain conditions. We used 3 chemical reagents to perform dissolution tests on these elastic fibers, and the results are shown in the table.
From the table, it can be seen that the chemical properties of PU and PTT and T-400 are obvious, but PTT and T-400 are both polyester fibers, and their chemical properties are very similar. Therefore, it is difficult to identify simply by using the dissolution method. Only by combining microscope observation method, combustion method, etc. can it be identified.
Summary
three elastic fibers were identified by combustion method, microscopy method, chlorine and nitrogen-containing color method and dissolution method. The identification of the three types of elastic fibers is as follows:
(1) PU fiber identification: It can be preliminarily determined as PU fibers through combustion; the longitudinal morphological characteristics can be observed through microscope, and it can be quickly distinguished from PTT and T-400 fibers. Through the chlorine-containing nitrogen-containing color reaction method or the use of sulfuric acid with a mass fraction of 75% as the solvent, it can be further distinguished from the other two elastic fibers and further verified as PU fibers.
(2) Identification of PTT and T-400 fibers: By burning, they are identified as polyester fibers; by observing the longitudinal and transverse morphological characteristics through a microscope, they can quickly distinguish PTT and T-400 fibers. The longitudinal shape of PTT fiber is single-bar shape, with a circular or approximately circular cross-section; while the longitudinal shape of T-400 fiber is double-bar-sided shape, with a dumbbell-shaped cross-section.
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