Classification And introduction Of Synthetic Fibers
Synthetic fiber is a chemical fiber produced by spinning and post-processing a synthetic linear polymer with suitable molecular weight and soluble (or fusible) properties. Compared with natural fibers and man-made fibers, synthetic fiber production is not limited by natural conditions. In addition to the general superior properties of chemical fibers, such as high strength, light weight, easy washing and quick drying, good elasticity, and resistance to mildew, synthetic fibers have certain unique properties.
filament
In the manufacturing process of synthetic fibers, after the spinning fluid (melt or solution) is formed by spinning and post-processing, the fibers with a length of kilometers are called filaments. Filament includes monofilament, multifilament and cord yarn.
Monofilament
It originally refers to a continuous single fiber spun with a single-hole spinneret, but in practical applications it often also includes 3-6 single fibers spun from 3-6 hole spinnerets. Thick synthetic fiber monofilaments (0.08-2mm in diameter) are called bristle filaments and are used to make ropes, brushes, daily net bags, fishing nets or industrial filter cloths; thinner polyamide monofilaments are used to make Transparent women's socks or other high-end knitwear.
Multifilament
A thread composed of dozens of single fibers. The multifilament of chemical fiber is generally composed of 8 to 100 single fibers. The vast majority of clothing fabrics are woven with multifilament yarns, because multifilament yarns composed of multiple single fibers are more flexible than single yarns of the same diameter.
cord yarn
The threads used to make tire cord fabrics are composed of more than a hundred to hundreds of single fibers, commonly known as cord yarns.
----------------------------short fibre----------------------------
Chemical fiber products are cut into lengths of several centimeters to more than ten centimeters, and fibers of this length are called short fibers. According to different cutting lengths, short fibers can be divided into cotton short fibers, wool short fibers, and medium-long short fibers.
01
Cotton type short fiber
The length is 25~38mm, the fiber is thin (linear density is 1.3~1.7dtex), similar to cotton fiber, and is mainly used for blending with cotton fiber, such as blending cotton-type polyester short fiber with cotton fiber to obtain a fabric. Called "polyester-cotton" fabric.
02
Wool type short fiber
The length is 70~150mm, the fiber is thick (linear density 3.3~7.7dtex), similar to wool, and it is mainly used for blending with wool. For example, wool-type polyester short fiber is blended with wool. The resulting fabric is called "wool polyester" "Fabric.
03
medium long fiber
The length is 51~76mm, the fiber thickness is between cotton type and wool type (linear density is 2.2~3.3dtex), and it is mainly used for weaving medium and long fiber fabrics. In addition to being blended with natural fibers, short fibers can also be blended with short fibers of other chemical fibers. The resulting blended fabric has good overall properties.
In addition, short fibers can also be spun pure. In the current production of chemical fibers around the world, the output of short fibers is higher than that of filaments. According to fiber characteristics, some varieties (such as nylon) mainly produce filaments; some varieties (such as acrylic) mainly produce short fibers; and some varieties (such as polyester) have a relatively close ratio of the two.
----------------------------Thick detail silk----------------------------
From the appearance of the thick and detailed yarn, you can see the alternating thick and detailed parts, and after the silk strips are dyed, you can see the alternating dark and light color changes. Thick and thin filaments are manufactured using uneven drafting technology after spinning. The difference in properties between the two resulting filaments can be controlled during production. Their distribution is irregular and in a natural state.
Thick and thin filament thick sections have low strength, long elongation at break, strong thermal shrinkage, good dyeability, and are easy to be processed by alkali reduction. These characteristics can be fully utilized to develop textiles with unique properties. The physical properties of thick and fine filaments are related to factors such as the diameter ratio of thick and fine filaments.
Generally, thick and thin filaments have high breaking elongation and boiling water shrinkage and low breaking strength and yield. Its strong shrinkage property can mix thick and fine filaments with other filaments to form different shrinkage mixed filaments. In addition, problems such as the easy deformation and low strength of thick sections of thick filaments should be paid attention to during the weaving, dyeing and finishing processes.
The initial thick and thin filaments were round wires. With the development of thick and thin filaments production technology, some special thick and fine filaments appeared one after another, such as special-shaped thick and fine filaments, mixed fiber thick and thin filaments, micro-porous thick and fine filaments, and fine-denier coarse filaments. Detail yarns, etc., which may have special feel and style, or have special absorbency, are mostly used to develop high-end fabrics.
----------------------------Textured yarn----------------------------
Textured yarns include all silk and yarns that have undergone texturing processing, such as elastic yarns and bulked yarns.
01
Elastic yarn
That is, deformed filament can be divided into two types: high elastic yarn and low elastic yarn. Elastic yarn has good stretchability and fluffiness, and its fabric is close to wool, silk or cotton fabrics in terms of thickness, weight, opacity, coverage and appearance characteristics.
Polyester elastic yarn is mostly used for clothing, nylon elastic yarn is suitable for producing socks, and polypropylene elastic yarn is mostly used for household fabrics and carpets. The main deformation methods include false twisting method, air injection method, hot air injection method, stuffing box method and shaping method.
02
Textured yarn
That is, using the thermoplasticity of polymer compounds, two synthetic fiber tops with different shrinkage properties are mixed in proportion. After heat treatment, the high-shrinkage top forces the low-shrinkage top to curl, making the mixed top stretchable and fluffy, becoming something like Textured yarn of wool. At present, acrylic bulked yarn has the largest output and is used to make knitted outerwear, underwear, wool, blankets, etc.
----------------------------Differentiated fiber----------------------------
Differentiated fiber is a foreign word originating from Japan. It generally refers to fiber materials obtained by physical deformation or chemical modification on the basis of original chemical fibers. It is significantly different from ordinary chemical fibers in appearance, properties or intrinsic quality. Differentiated fibers not only improve and enhance the performance and style of chemical fibers, but also give chemical fibers new functions and characteristics, such as high water absorption, electrical conductivity, high shrinkage and dyeability.
Since differentiated fibers are mainly used to improve simulation effects, comfort and protection, they are mainly used to develop clothing textiles that imitate wool, linen, and silk. Some of them are also used to develop paving textiles and industrial textiles.
----------------------------Special-shaped fiber----------------------------
In synthetic fiber spinning and forming processing, fibers or hollow fibers with non-circular cross-sections spun using special-shaped spinnerets are called special-shaped cross-section fibers, or special-shaped fibers for short. At present, there are dozens of types of special-shaped fibers. About 50% of the polyester fibers, polyamide fibers and polyacrylonitrile fibers sold on the market are special-shaped fibers.
It should be noted that the cross-section of fibers obtained by wet spinning with circular spinnerets (such as viscose fiber and polyacrylonitrile fiber) is not perfectly circular, but may be zigzag-shaped, kidney-shaped or dumbbell-shaped. Despite this, they cannot be called profiled fibers. Special-shaped fibers with different cross-sections have different properties and play different roles in textile development. Compared with ordinary round fibers, special-shaped fibers have the following characteristics:
01
Gloss and feel
The luster of the fiber is related to the cross-sectional shape of the fiber. Triangular cross-section yarn and trilobal cross-section yarn have a shining luster, which improves the "aurora" phenomenon of round fibers. For example: blended fabrics of triangular cross-section polyester fiber or polyamide fiber and other fibers have a flash effect and are suitable for the development of silk-like fabrics, wool-like fabrics and various velvet fabrics. Synthetic fibers with flat, ribbon-like, dumbbell-shaped cross-sections have the feel and luster of fibers such as linen, antelope wool, and rabbit fur.
The polyester filament with a five-lobed cross-section has a sheen similar to silk, while resisting pilling, and has good feel and coverage. In addition to being shiny, polygonal cross-section yarn has strong covering power and soft hand feel. It is mostly used to make textured yarn to make knitted fabrics and socks. Its short fibers are used for blending to make a variety of wool-like fabrics and blanket products. The luster of rectangular cross-section silk is soft, close to the luster of silk and animal hair. The blend of its short fiber and cotton fiber has a woolen style, and blended with wool, you can get a fabric with unique luster.
02
Mechanical properties, water absorption and dyeability
Special-shaped fibers are more rigid, their resilience and coverage can also be improved, and their strength is slightly reduced. In addition, special-shaped fibers have a larger surface area, enhanced water and steam transmission capabilities, fast drying speed, and good dyeability.
03
Pilling resistance, loft and breathability
Fibers with flat cross-section shapes can significantly improve the phenomenon of pilling, and the greater the flatness, the better the effect. For example, after polyester and polyamide flat cross-section fibers are blended with wool, the fabrics are generally less prone to pilling. Special-shaped fibers usually have good fluffiness. The fabric feels plump and has strong warmth retention. Due to the increase in pores, it has good air permeability. As the irregularity of the cross section increases, its fluffiness and air permeability also increase.
04
Hollow fiber specificity
Hollow fibers have excellent warmth retention and fluffiness. Some hollow fibers also have special uses, such as making reverse osmosis membranes for artificial kidneys, seawater desalination, sewage treatment, hard water softening, solution concentration, etc.
----------------------------Composite fiber----------------------------
There are two or more immiscible polymers on the cross-section of the fiber. This kind of chemical fiber is called composite fiber, or bicomponent fiber. Because the two or more components contained in this fiber complement each other, the performance of composite fibers is usually better than that of conventional synthetic fibers and has many uses.
There are many varieties of composite fibers, which can be divided into two categories according to their shapes, namely double-layer type and multi-layer type. Double-layer type includes side-by-side type and skin-core type, and multi-layer type includes side-by-side multi-layer type, radial type, multi-core type, wood grain type, embedded type, island type and split type, etc.
The main characteristic of side-by-side composite fiber is high crimping, which can make the fabric fluffy, soft, warm and wool-like style. It is mainly used in bulked wool, knitted fabrics, socks and blanket products. Sheath-core type composite fiber is divided into two types: partial sheath-core type and concentric sheath-core type. The former type has three-dimensional curling property, but the curling property is not as good as the side-by-side type composite fiber.
Depending on the properties of different polymers and their distribution positions on the fiber cross-section, many composite fibers with different properties and uses can be obtained.
For example: when using side-by-side composite and partial sheath-core composite, due to the different thermoplasticity of the two polymers or the asymmetric distribution on the fiber cross-section, a shrinkage difference occurs during the post-processing process, resulting in spiral curling of the fiber, which can be made with Composite fiber with elasticity and fluffiness similar to wool.
Sheath-core composite fiber is a fiber that combines the characteristics of two polymers or highlights the characteristics of one polymer. For example, using nylon as the skin layer and polyester as the core layer can produce fibers with good dyeability and soft but stiff feel; using Optical fibers can be made from a high refractive index core layer and a low refractive index skin layer.
If the island component is continuously dispersed in the sea component to form a sea-island composite fiber, and then the sea component is dissolved with a solvent, leaving the continuous island component, very fine ultra-fine fibers can be produced. Split-type composite fibers appear in the form of thicker filaments during spinning and post-processing.
----------------------------superfine fiber----------------------------
Since the thickness of single fibers has a great influence on the performance of fabrics, chemical fibers can also be classified according to the thickness (linear density) of single fibers and are generally divided into conventional fibers, fine denier fibers, ultra-fine fibers and ultra-fine fibers.
Conventional fiber linear density is 1.5~4dtex.
The linear density of fine denier fiber is 0.55~1.4dtex, which is mainly used for light or medium-thick fabrics that simulate silk.
The linear density of ultrafine fiber is 0.11~0.55dtex, and it can be produced by two-component composite splitting method, island method, melt-blown method, etc.
Ultra-fine fibers have a linear density below 0.11dtex and can be produced by island spinning. They are mainly used in special fields such as artificial leather and medical filter materials.
Compared with conventional synthetic fibers, microfibers have the advantages of soft and waxy feel, soft luster, strong fabric coverage, and good wearing comfort. They also have the disadvantages of poor wrinkle resistance and high dye consumption during dyeing. Its main performance is detailed in the table below. Microfiber is mainly used to make high-density waterproof and breathable fabrics, artificial leather, imitation suede, imitation peach skin, imitation silk fabrics, high-performance wipes, etc.
----------------------------New synthetic fiber----------------------------
The new synthetic fiber adopts new modification and composite technology in every step from polymerization, spinning, weaving, dyeing, finishing and sewing. It is a new fiber material that is unmatched by natural fibers and synthetic fibers in the past. According to its product form, new synthetic fibers mainly include ultra-fluffy, ultra-draping and ultra-fine types. According to their feel, they can be divided into silk feel, peach skin feel, ultra-fine powder feel and new wool feel.
01
Super fluffy
Among all synthetic fiber products for consumption, ultra-fluffy and high-texture fibers are the most common, and almost all of them are made of different shrinkage mixed fibers or multi-phase mixing technology. In order to improve the bulkiness of fiber products, high thermal shrinkage polymers and low shrinkage potential spontaneous elongation filaments have been developed to achieve better bulkiness in fabrics.
02
Ultra-slim
As a new synthetic fiber, ultrafine fiber has a very low linear density. The linear density of some varieties reaches less than 0.001dtex. It is mainly spun using composite spinning ultra-fine technology. The peach skin fabric thus developed has an ultra-soft and delicate feel that is difficult to match with natural fiber products.
03
Super hanging type
Super draping fibers add inorganic microparticles to the spinning solution. After spinning, reduction processing is performed to eliminate the inorganic microparticles and form numerous microscopic pits on the fiber surface. Due to the reduced friction between monofilaments, super-draping fiber products have super-draping properties and a unique feel that is unmatched by natural fibers.
----------------------------Easily dyeable synthetic fibers----------------------------
Synthetic fibers, especially polyester fibers, have poor dyeability and are difficult to dye into dark colors. Chemical modification can improve the dyeability and dyeing depth. This modified synthetic fiber is called dyeability. Synthetic fibers mainly include cationic dyeable polyester fiber, cationic deep-dyed polyamide fiber, and acid-dyeable polyacrylonitrile fiber and polypropylene fiber. Easily dyeable synthetic fibers not only expand the dyeable range of fibers and reduce the difficulty of dyeing, but also increase the variety of textile designs and colors.
----------------------------high performance fiber----------------------------
High-performance fibers have special physical and chemical structures, and one or more performance indicators are significantly higher than ordinary fibers, and the acquisition and application of these properties are often related to aerospace, aircraft, oceans, medicine, military, optical fiber communications, bioengineering, and robotics. It is related to high-tech fields such as large-scale integrated circuits, so high-performance fibers are also called high-tech fibers.
High-performance fibers are usually distinguished by their special properties, such as high strength and modulus, high adsorption, high elasticity, high temperature resistance and flame retardancy, light guide, electrical conductivity, efficient separation, radiation protection, reverse osmosis, corrosion resistance, medical and Pharmaceutical fiber and other fiber materials. High-performance fibers are mainly used in the manufacture of industrial textiles, but some of them can also be used to develop decorative textiles and clothing textiles, and the performance of these two types of textiles can be significantly improved.
----------------------------Nanofibers----------------------------
Fibers with a diameter less than 100nm are usually called nanofibers (1nm is equal to 10 m, that is, 10 μm, which is only the length of 10 hydrogen atoms). At present, some people also add nanoscale (ie, particle size less than 100nm) powder filling Material fibers are called nanofibers.
At present, the thinnest nanofiber is a chain of single carbon atoms. This kind of carbon nanotube is known as the king of nanomaterials. The reason is that this material, which is so thin that it is difficult to observe with ordinary instruments, has magical abilities: ultra-high strength, ultra-high strength, and ultra-high strength. Flexible and strangely magnetic. Because the distance between carbon atoms in carbon nanotubes is short and the diameter of the tube is small, the fiber structure is less prone to defects. Its strength is 100 times that of steel and 200 times that of ordinary fibers, while its density is only 1/6 of steel. A rope made of it can be pulled from the earth to the moon without being broken by its own weight.
It has strange electrical conductivity, with both metal conductivity and semiconductor properties. Even different parts of a carbon nanotube can show different conductivities due to structural changes. Using it to make rectifiers can replace silicon chips, which will cause major changes in electronics and make computers extremely small.
Nanodevices made of carbon nanotubes can be used to assemble nanorobots, such as mosquito planes and ant tanks, which can be used in military and medical applications. Carbon nanotubes can be used to make hydrogen storage materials and develop hydrogen into a clean energy source for human services. In addition, carbon nanotubes can also be used as stealth materials, catalyst carriers and electrode materials. Nanofibers can support the arrangement of "nano machines" and connect the integrated array of "nano machines" into large-scale systems.
When the fineness of most materials reaches the nanometer level, their physical and chemical properties show unconventional properties, such as:
01
surface effect
The smaller the particle size, the larger the surface area. Since the surface particles lack the coordination of adjacent atoms, the increase in surface energy is extremely unstable. It is easy to combine with other atoms and show strong activity. After the fineness of the fiber reaches the nanometer level, the relationship between its diameter, specific length and specific surface area is shown in the table below.
02
small size effect
When the size of the particle is similar to or smaller than the wavelength of the light wave, the de Broglie wavelength of the conduction electron, and the coherence length or transmission depth of the superconducting state, its periodic boundary conditions will be destroyed, and the particle's acoustic, Light, electromagnetic, thermodynamic and other properties will change, such as melting point reduction, color separation and discoloration, absorption of ultraviolet rays, shielding of electromagnetic waves, etc.
03
quantum size effect
When the particle size is small to a certain value, the electron energy level near the Fermi level changes from quasi-continuous to discrete energy levels. At this time, the material that was originally a conductor may become an insulator, and the material that was originally an insulator may become a superconductor. .
04
Macroscopic quantum tunneling effect
The tunnel effect means that tiny particles can pass through an object under certain circumstances, just like there is a tunnel inside. The manufacturing of nanofibers can be roughly divided into three categories: molecular technology preparation methods, spinning preparation methods, and biological preparation methods.
Keywords: synthetic staple fiber wool synthetic fibre woven synthetic fibers synthetic textile synthetic textile fibers synthetic wool roving
