Since large-scale industrialization, the development speed, technical level and production variety of polyester are far greater than other synthetic materials and synthetic fibers. The main target market for polyester fibers is to replace some natural fibers, especially cotton fibers. In 2009, the world's polyester production reached 48.1 million tons, of which my country's polyester fiber production accounted for about 70%. And, as one of the pull-ups ingredients, it is widely used.
Super imitation cotton is the use of synthetic fibers to improve the handle and other properties of the fabric in some way. Appearance, feel, and various functions are equivalent to pure cotton fabrics, while maintaining the performance of synthetic fiber fabrics. In addition, there are few researches on super cotton-like polyester in the non-woven field, and some researches apply it to the hygiene products industry such as pull-ups.
The benzene ring chain and the methylene chain exist in the macromolecular chain of polyester, and both are rigid and flexible. Generally speaking, macromolecules are mainly rigid. Due to the lack of hydrophilic groups in the polyester macromolecular chain, the fiber hygroscopicity is very low, and the moisture regain is only about 0.4%.
Polyester modification methods can be divided into two categories: one is chemical modification, which uses chemical methods such as copolymerization and chemical branches to change the structure of the macromolecular chain to improve the chemical properties of polyester fibers; the second is physical modification, using cross-section. Physical indicators such as cross-sectional shape of polyester fibers can be improved by methods such as special-shaped and mixed.
(1) Chemical method
①Molecular structure modification
During the synthesis of polyester chips, modifying monomers were introduced to modify the polymer. Usually there are block polymerization, alternating copolymerization, random copolymerization and so on. The advantage is that polyester can be fundamentally modified from the molecular structure, and the modification effect is lasting. However, this method also makes the fiber lose some of its original excellent properties, such as fiber strength and temperature resistance.
The graft modification method refers to the process of introducing modified monomers into the polymer surface in the form of branched chains under certain conditions. Commonly used grafting methods include radiation grafting and chemical grafting. Generally, compounds containing hydrophilic groups such as hydroxyl groups, carboxyl groups and acid amine groups are selected.
Surface modification usually involves adding a layer of modifying compound to the surface of the fiber or fabric. The methods used are generally surfactant modification, alkali reduction treatment and plasma treatment. The advantage is that the process is simple and the modification effect is obvious; the disadvantage is that the washing resistance is poor, and the durability of the modification effect is poor.
(2) Physical method
① Blending modification
Blending is to uniformly mix polyester polymer and modified components in a softened or melted state, and then form them by physical methods such as extrusion to improve certain properties of polyester. The advantage is that it is relatively simple to implement, but the melting conditions are similar between the higher blends.
② Blending method
The composite method means that each fiber spun contains a variety of properties after passing through a spinning distribution device with a special structure. Common composite fiber shapes are sheath-core and sea-island.
③ Microporous fiber structure
The method is based on the principle of capillary water absorption, and the main purpose is to change the morphological structure of the fiber, so that it has internal and external micropores, and improves the water absorption and permeability of polyester. But this method can only improve the water absorption of the fiber, because it is only the structure of micropores, which increases the surface area and thus improves the water absorption performance.
④Irregularization of fiber cross section
Cross-section profiled refers to the preparation of fibers with non-circular cross-sections by changing the shape of the spinneret holes and adjusting the spinning process parameters. The special-shaped sections of common fibers mainly include triangular, cross, trilobal, flat, special-shaped hollow and star.
Although the application of super cotton-like polyester fiber needs further improvement in the application of pull-ups, from the perspective of the whole analysis, the use of this material is conducive to the upgrading of products. The key lies in how researchers can make good use of the material's greatest characteristics.
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