There is no international consensus. The US PET Neighborhood Committee defines fibers with a monofilament fineness of 0.3～1.0 dtex as superfine fibers, Japan defines fibers with a monofilament fineness below 0.55 dtex as ultrafine fibers, and Italy defines monofilaments as monofilaments. Fibers with a fineness of 0.5 dtex or less are defined as ultra-fine fibers, but most people think that those with a monofilament fineness less than 1 dtex are ultra-fine fibers, and those with a single filament fineness of less than 0.1 dtex are considered ultra-fine fibers. my country’s textile industry believes that fibers with a monofilament fineness less than 0.44 dtex are defined as ultrafine fibers. Most synthetic fibers can be prepared into ultrafine fibers, such as polyamide, polyester, polypropylene, polyacrylonitrile and other fibers.
Superfine fibers are mainly divided into superfine natural fibers and superfine synthetic fibers. Ultra-fine natural fibers mainly include animal fibers (spider silk, silk, leather, animal hair, etc.), plant fibers, etc.; ultra-fine synthetic fibers mainly include polyester, polyamide, polyacrylonitrile, polypropylene, polytetrafluoroethylene, and glass Fiber and other fiber varieties, the largest output in the industry is polyester and polyamide two kinds of ultrafine fibers.
Superfine natural fiber
- Animal fiberIn order to survive and develop, organisms in nature have created a series of optimal compositions and structures under the promotion of external environment, so that organisms have special structures and functions to adapt to natural environmental changes. For example, the diameter of the silk that spiders spit out under normal circumstances is 0.5-1.0μm, has good toughness (elongation at break of 14%), and has a strong ability to withstand heavy objects or strong external impacts. It can be used to prepare body armor and body armor worn by soldiers. The protective cover of military machinery can also be used in aerospace, construction, medicine, health care and other fields, and has huge potential application value. Silk is another important natural protein fiber. It is composed of silk fibroin and sericin wrapped around the silk fibroin. Each silk is composed of two single fibers side by side. The linear density of the fiber after degumming is 1.1~1.3 dtex. The strength of silk is high, the elongation at break can reach 15%~25%, and the abrasion resistance is better than other natural fibers. It also has important applications in the medical, textile and military fields. In addition, animal fur (the microfibril diameter of wool fibers is 10-15nm) and the fibril linear density in the cortex are both less than 1.1dtex, which is the main reason for the excellent performance of natural leather, and has become the first choice for bionic research and artificial leather manufacturing.
- In addition to animal fiber, plant fiberis another natural fiber with excellent performance. It is mainly distributed in the thick-walled tissues of seed plants. The basic component is cellulose, which is a polymerization of 7000~10000 glucose molecules connected by glycoside chains. Things. As an outstanding representative of ultra-fine natural plant fibers, the diameter of cotton fiber is 10-17μm, which constitutes the smallest unit of cotton fiber-the diameter of microfibril is about 6nm. It is widely distributed on the surface of plant seeds, which is the theoretical research and industrialization of the textile industry. Important raw material for application. In addition, in plant stems, some hemp herb stems. For example, ramie, jute, flax, etc., have relatively developed fiber bundles with fiber diameters between 10 and 40 μm, which are important sources of raw materials for industrial textiles.
Superfine synthetic fiber
Mankind has found a lot of inspiration from the development and evolution of natural organisms, and has developed many ultra-fine synthetic fibers, which are soft to the touch, excellent in drape, and comfortable to wear. They are currently the focus of research and development of ultra-fine fibers in various countries in the world. Various types of synthetic fibers in the industry, such as polyester, polyamide, polyacrylonitrile, polypropylene, etc., can be obtained through certain technical means to obtain ultra-fine fiber varieties. At present, the industrialization of ultra-fine polyester is more mature than other fibers, and it occupies a dominant position in textile fibers.
The most notable feature of superfine fiber is that its monofilament linear density is much lower than that of conventional ordinary fiber, and the thinnest can reach 0.0001 dtex. Due to this remarkable feature of superfine fiber, it has many properties different from ordinary fiber, mainly in the following aspects:
(1) It feels soft and delicate and has good flexibility
The cross-section diameter of the monofilament of the superfine fiber and the fineness of the monofilament are both smaller than that of the natural fiber, so its crimp modulus is lower, so the fabric feels soft and has better performance; its monofilament has low bending stiffness, so its fabric has Good drape performance; Compared with ordinary fibers, the crystallinity and orientation of ultrafine fibers are higher, which improves the relative strength of the fibers. Therefore, the bending strength and repeated bending strength of the fibers are improved, making them more flexible and smooth. And it feels soft. However, these properties are also related to its fabric structure, blended fiber components, blended fiber ratio, etc. At the same time, for textured yarns, the drop in monofilament fineness will lead to poor bulkiness.
(2) Good wrinkle resistance and abrasion resistance
The decrease in microfiber fineness reduces its absolute strength. However, for the same yarn number, the number of fibers in the cross section of the yarn is more than that of conventional yarns, so the yarn strength is still relatively high; at the same time, it is beneficial to sanding the fabric. Washing or raising treatment to prepare higher-grade fabrics such as velvet, suede and peach skin, and has better wrinkle resistance and abrasion resistance.
(3) Good fluffy and soft luster
The microfiber has small fineness and high fiber density, which increases the specific surface area and capillary effect of the fiber. While improving the coverage and bulkiness of the fabric, the reflection of light is also more dispersed, so that the reflected light inside the fiber is more distributed. It is delicate, so the luster is soft, giving it a silk-like luster.
(4) High-density fabric structure and high cleaning ability
Superfine fibers are thin, and the warp and weft yarns are easy to adhere to each other and squeeze deformation during weaving, so that it is easy to form a high-density fabric. The warp and weft density is several times that of ordinary fabrics. After finishing, even without any coating, etc. The treatment can also prepare waterproof fabrics, which can be used in raincoats, windbreakers, casual wear, sportswear, dust-free clothing, fashion and footwear fabrics, etc. Similarly, due to its small monofilament density, when wiping objects with its woven fabric, the thin fibers are like sharp scrapers, which makes it easy to scrape off the dirt. At the same time, the contact surface between the ultrafine fibers and the dirt is larger. Therefore, it is easier to stick tightly and has a strong capillary wicking effect, so that it is easy to absorb the attached dirt into the fabric, and to avoid the re-contamination of the object due to the loss of the dirt. Therefore, it has high cleaning ability and is an ideal wiping cloth. First choice with clean cloth.
(5) Good warmth retention
The fineness of superfine fiber is small, and there is more still air in the fiber assembly, so superfine fiber is a better thermal insulation material. If some thicker fibers are mixed into the fiber assembly as a scaffold, the compression elasticity and bulkiness can be greatly increased.
(6) Higher water absorption and oil absorption
The fineness of the superfine fiber becomes thinner and the specific surface area becomes larger, thereby forming a smaller scale and a larger number of capillary holes, which not only greatly improves the moisture absorption of the fabric, but also greatly improves its capillary wicking capacity. Can absorb and store more liquid (oil or water). Therefore, microfibers can be used in the development of super absorbent products, such as super absorbent pen cores, super absorbent towels and other products. These voids can absorb a large amount of water, so the ultra-fine fibers have strong water absorption, and most of the absorbed water is stored in the voids, which can be dried quickly, thereby effectively preventing the growth of bacteria.
(7) A good carrier for biological enzymes and ion exchange
Because of the large specific surface area of superfine fibers. Therefore, it is a good carrier for active agents such as biological enzymes and ion exchangers, which can improve its activity efficiency, and can also be used in permeable membranes, biomedicine (such as artificial skin, artificial blood vessels) and other fields.
In addition, the superfine fiber also has anti-microbial adhesion and anti-corrosion of shellfish and seaweed. However, there are also certain problems in the processing and use of superfine fibers. Such as: high friction coefficient, low monofilament strength, and reduced bending stiffness, which reduces the stiffness and bulkiness of the fabric prepared; the large specific surface area makes it difficult to desizing, high slurry absorption, and large dye consumption during processing. Dyeing is easy to be uneven and other problems. Therefore, it is necessary to appropriately adjust the dyeing and finishing equipment and related process conditions during the processing and preparation process.
(1) Imitated silk fabric: The level of the artificial silk of superfine fiber and the imitation of other natural fibers (wool, cotton, hemp) is getting higher and higher, and the simulation effect is becoming more and more realistic, even reaching the level of fake and real.
(2) Imitation peach skin fabric: This is a clothing fabric with good quality and unique style. The imitated peach skin fabric woven with microfibers has extremely short and good-feeling hair on the surface, just like the fine short hair on the surface of a peach, with a soft, delicate and warm hand feeling. The high-end fashion clothes, jackets, T-shirts, underwear, culottes, etc. woven with this fabric are cool and comfortable, not close to the body, and full of youthful beauty.
(3) Super absorbent material: mainly used for super absorbent towels, paper towels, pen cores, sanitary napkins, diapers, etc. According to reports, the super absorbent towel developed by the Japanese small material pharmaceutical company has a water absorption speed more than 5 times faster than ordinary towels, and it absorbs water quickly and feels very soft and comfortable when used.
(4) High-density waterproof and vapor-permeable fabric: a high-density fabric woven from superfine fibers, which not only has the function of waterproofing, but also has the properties of vapor and moisture permeability, lightness, and easy folding and carrying. Skiing, skating, swimming and other sportswear made of microfiber can reduce resistance and help athletes create good results.
(5) Clean cloth and dust-free clothing: Superfine fibers can absorb dust, particles, and liquids 7 times their mass. The clean cloth made of microfiber has strong cleaning performance. It removes dirt quickly and thoroughly, and does not shed hair. It can be reused after washing. It can be used in precision machinery, optical instruments, microelectronics, clean rooms and households. It has been widely used in all aspects, and it is also an ideal choice for dust-free clothing.
(6) Imitated suede and artificial leather: knitted or woven cloth made of superfine fibers, immersed in polyurethane solution after sanding or napping, and dyeing and finishing to obtain suede And artificial leather, with the characteristics of high strength, light weight, bright color, mildew and mothproof, good flexibility, etc., it is famous in the clothing industry for its advantages of lightness, thinness, softness, firmness, weather and rain, and low price.
(7) Other applications: Ultrafine fibers have been widely used in medical materials such as thermal insulation materials, filter materials, ion exchange, artificial blood vessels, artificial skin, and biological engineering. In the production of nonwovens, superfine fibers have been successfully used in the weaving of high-grade synthetic leather base fabrics and artificial suedes, and can also be used for meltblown nonwovens, spunlaced nonwovens, and needle punched nonwovens. Weaving cloth and other products.
News report: The filter layer of the mask is mainly composed of polypropylene meltblown ultrafine fibers. It is very thin and not resistant to high temperatures. When the temperature is greater than 80 degrees, it will shrink and deform, causing structural damage and reducing the protective effect. The entry of water will also cause the charge in the filter layer to quickly disappear, resulting in a significant drop in the filtering effect.