WHAT IS MODIFIED FIBER?
Modified fiber, also known as functional fiber, refers to a product derived from chemical or physical methods to improve some properties of conventional chemical fiber varieties (such as hygroscopicity, dyeing, antistatic, flame retardancy, etc.). The general term for a series of new functional fibers. This is similar to the usual rubber modification, plastic modification, etc.
Usually, the clothes people wear are woven from fibers, and the raw materials may be natural materials or synthetic, but the state of the raw materials is not necessarily perfect, for example, they may not be dyed well, so it needs to be transformed through a series of methods so that the fiber is more suitable for use, which is the most common application of fiber modification in life. Traditional modification methods include a chemical method and physical method, and a biological method has also been developed in recent years.
The main goal of synthetic fiber modification is to give it the properties of natural fibers or to meet the needs of special properties, such as high strength, high modulus, high elasticity, heat resistance, and various special functions. Simply put, it is to add skill points to fibers.
To this end, it is necessary to have a systematic and profound understanding of the relationship between the structure and properties of natural fibers and synthetic fibers. However, imitating natural fibers is not simply to reproduce their tissue structure, but more importantly, to simulate the functions of natural fibers by modifying their fibers. However, due to the intricate relationship between fiber structure and properties, when a certain method is used to improve a certain property, it will inevitably lead to changes in other properties. For example, when copolymerization is used to improve the hygroscopicity or dyeability of hydrophobic synthetic fibers, it is often accompanied by a decrease in melting point or a decrease in strength. Therefore, it is necessary to prevent the valuable properties of the fibers from being unduly affected by the modification. A comprehensive balance or “additive effect” should be obtained among the contradictory effects, so that the fiber material can obtain higher use value and wider use.
Common fiber modification methods
- Physical method
Physical modification usually uses various physical methods and means to improve the properties of fibers by changing the aggregated structure, morphological structure, and surface components of the fibers without changing the main structure of the fiber-forming polymer macromolecules. The formation of ceramic fibers and metal fibers and the transformation of crystal phase structure is usually related to the regulation of melt spinning and sintering methods, which are the results of physical modification and processing methods.
- Biological method
This is a new modification method that has only appeared in recent years. It uses biotechnology, such as genetic engineering and biosynthesis, which can not only increase the way to modify fiber products and improve the properties of existing fibers but also create Some brand new “biofibers”. This is the synthesis of chemistry and biology. Development status of new functional textile materials in my country.
- Chemical method
Chemical modification of polymers is a kind of modification method that changes the types of atoms or original groups of macromolecules and their bonding methods through chemical reactions of polymers. After chemical modification, the chemical structure of existing macromolecules is changed, thereby improving the properties of fibers or giving them new properties. The effect of chemical modification is durable, but the change of chemical structure will also cause some changes in structure to a certain extent, which will lead to changes in a series of properties of fibers.
At present, my country’s functional fiber materials have reached the international advanced level, which is characterized by the multi-functionalization and high performance of conventional fibers, and has the functions of flame retardant, antibacterial, and antistatic, such as silicon-nitrogen flame retardant viscose staple fiber, polyacrylonitrile pre-oxidized fiber, flame retardant polyester, flame retardant nylon, conductive polyester-nylon composite fiber, conductive meta-aramid fiber, copper carbon nano-polyamide 6 ecological antibacterial fiber, polylactic acid ecological antibacterial fiber, ultra-fine denier Porous recycled polyester ecological antibacterial fibers, special-shaped polyamide 6 ecological antibacterial fibers, etc., are mainly used in special military uniforms and firefighting uniforms, aircraft and high-speed rail interior materials, high-end textiles, medical hygiene materials, and other fields.
At the same time, “Made in China 2025” proposes the development of new materials, high-value biomedical materials, energy conservation, and environmental protection, resource recycling, fashion apparel, mid-to-high-end home textiles, industrial textiles, and other important content, and the development of aerospace, marine equipment, and wind power equipment. , key materials for new energy vehicles, etc.
Common Modified Fiber Types
- Surface micro-pit grooves and high specific gravity fibers
High-specific gravity fibers can be obtained by blending inorganic particles and organic materials to improve the drape of the fabric. When the fiber mixed with inorganic particles is reduced in alkali, the polymer around the inorganic particles is hydrolyzed, and many crater-like micropores appear on the surface of the fibers. This surface imparts a cooling feel to the fabric.
- High shrinkage fiber
① Low shrinkage acrylic fiber
During heat treatment, fibers with a shrinkage rate of 20-50% (70%) (generally, the boiling water shrinkage rate of fibers is not > 5%, and the filament is not > 9%).
② High shrinkage acrylic fiber
During heat treatment, the shrinkage rate in boiling water reaches 15-45%; for high-shrinkage polyester, the shrinkage rate in boiling water reaches 30-50%.
- Self-stretching filament
Refers to the characteristic of self-elongation during heat treatment. Its self-elongation can reach 8-15%. The self-stretching filament is compounded with high-shrinkage and low-shrinkage filaments to form a high-isolation-shrinkage composite filament, and the shrinkage difference between the components can reach 30-45%.
After finishing, the low-shrinkage silk floats on the surface of the fabric, forming a dense ultra-short wave silk circle and a peach skin feel. High shrinkage filaments are concentrated on the inside of the fabric as a skeleton.
Easy dyeing means that it can be dyed with different dyes, and the color is bright, the color spectrum is complete, the color tone is uniform, the color fastness is good, and the dyeing conditions are mild. Polyester is the most difficult fiber to dye among the commonly used synthetic fibers, and the easy-to-dye synthetic fibers mainly refer to the dyeing and modified fibers of polyester. The common varieties of easy-dyeing synthetic fibers include cationic dyeable polyester, normal temperature, and normal pressure cationic dyeable polyester (ECDP), acid dyed polyester, acid or basic dyed polyester, acid dyed acrylic fiber, Dyeable nylon fiber, cationic dyeable nylon fiber, etc.
- Water-absorbing and hygroscopic fiber
Water-absorbing and hygroscopic fibers are fibers that have the ability to absorb moisture and transport it to adjacent fibers. Compared with natural fibers, most synthetic fibers have poor hygroscopicity, especially polyester and polypropylene fibers. To improve the hygroscopicity and comfort of synthetic fibers, chemical modification methods and physical modification methods can be used to improve the wetting and expansion of fibers through modification. ability, or make porous fibers to form a micro-pore system inside to increase the water and moisture absorption capacity of the fibers. Water-absorbing and hygroscopic fibers are mainly used in functional underwear, sportswear, training clothes, sports socks, and other products.
- Mixed filament
Mixed filaments refer to multifilaments composed of monofilaments with different geometrical or physical properties. The purpose is to improve the natural feel of synthetic fibers. There are several types of commonly mixed fiber yarns, such as different shrinkage, special shape, different denier, and multi-differential mixed fiber.
① Special-shaped mixed filament yarn
The mixed filament yarn composed of monofilaments with different cross-sectional shapes has voids and capillary structures between the fibers, which can reduce the friction coefficient between the fibers, and the fabric has good bulkiness, hygroscopicity, and resilience.
② Different shrinkage mixed filament yarn
Different shrinkage mixed fiber is a composite fiber composed of high shrinkage fiber and ordinary fiber. During the process of fabric finishing and post-processing, the high shrinkage fiber shrinks due to heat and becomes the core fiber, and the fiber with a low shrinkage rate floats due to the difference in fiber length. Out of the surface, and produce curling, while the formation of gaps between the fibers, gives the fabric a fluffy feeling.
③ Different denier mixed silk
Microfiber fabrics have good softness and drapability, but often have no body bones. In order to pursue a soft but not rotten style, a different denier blending method of blending coarse denier fibers and microfibers can be used.
④ Multi-differential mixed filament yarn
It refers to the combination of fibers with various characteristics such as linear density, cross-sectional shape, thermal shrinkage, elongation, uneven thickness of monofilament, etc. in different forms. The purpose is to make it closer to natural fibers. style.
Conclusion
Through modification, fibers have more excellent physical, chemical, mechanical, functional, and other characteristics. Using the advantages of modified fibers, they can be used in a wider range of fields such as protection, reinforcement, high temperature, and filtration.