Get a comprehensive understanding of aramid functional textiles

Get a comprehensive understanding of aramid functional textiles

Aramid full name aromatic polyamide fiber, a new type of high-tech synthetic fiber, with ultra-high strength, high modulus and high temperature resistance, acid and alkali resistance, light weight and other excellent properties, its strength is 5~6 times of steel wire, modulus is 2~3 times of steel wire or glass fiber, toughness is 2 times of steel wire, and the weight is only about 1/5 of steel wire, at a temperature of 560 degrees, no decomposition, no melting. It has good insulation and anti-aging properties, and has a long life cycle. It is a kind of high strength, high modulus, low density and good wear resistance high temperature flame retardant fiber, its technical content, high added value, excellent mechanical, chemical stability and mechanical properties, can not only be used alone as a variety of structural materials and functional materials, but also can be used in combination with other materials. In addition, it also has good rebound performance and sealing performance, no harm to human health and the environment, can be used as a seal for water, oil, hydrocarbons and medium strength acid and alkali and other media, the gasket produced has excellent sealing performance and creep relaxation resistance. It can be used as an alternative to asbestos in friction sealing materials, high-performance heat-resistant insulating paper and reinforced composite materials.

1. The main varieties of aramid

Commercial aramid mainly includes meta-aramid and para-aramid, meta-aramid mainly includes DuPont’s Nomex, Teijin Conex, etc.; Para-aramid mainly includes Kevlar (DuPont), Technora (Teijin), Twaron (Teijin) and so on.

2. Research and application status of aramid functional textiles

The unique physical and chemical properties of aramid make it widely used in functional textiles with high temperature resistance, flame retardant, wear resistance and high strength. Research on it is also in the ascendant around the world, new functional textiles are emerging one after another, and the application field is constantly expanding.

Aramid fiber is an important national defense material, in order to meet the needs of modern warfare, at present, the United States, Britain and other developed countries of body armor are aramid material, aramid body armor, helmet lightweight, effectively improve the army’s rapid response ability and lethality. In the Gulf War, American and French aircraft used a large number of aramid composite materials. In addition to military applications, it has been widely used as a high-tech fiber material in aerospace, electromechanical, construction, automobiles, sporting goods and other aspects of the national economy. In aviation, aerospace, aramid because of its light weight and high strength, saving a lot of power fuel, according to foreign data, in the launch of the spacecraft, every 1 kg of weight reduced, means a reduction of 1 million US dollars. In addition, the rapid development of science and technology is opening up more new civil space for aramid. According to reports, at present, aramid products are used in body armor, helmets, etc. about 7~8%, aerospace materials, sports materials account for about 40%; About 20% of tire frame materials and conveyor belt materials and high-strength ropes account for about 13%.

2.1 Aramid flame retardant series textiles

Although aramid fiber has good heat resistance and flame retardancy, it is relatively expensive. Secondly, due to the high crystallinity of molecules and the strong intermolecular bondage, staining is difficult. The high price and difficulties in dyeing have inhibited its yield and variety development to some extent. Therefore, a variety of aramid blended flame retardant fabrics have been researched and developed to improve the dyeing effect and reduce the price of products.

(1) Aramid and wool blended flame retardant fabric Wool is a natural fiber with certain flame retardant properties, aramid staple fiber is first formed into strips, and then mixed with wool strips into yarn, and then weaved. When the proportion of aramid blending exceeds 30%, its limiting oxygen index reaches more than 28, and the fabric can achieve good, long-lasting flame retardant performance without flame retardant finishing, and can reduce costs without affecting the appearance and comfort of the fabric. The blending ratio can be adjusted according to the application to achieve multi-functionality.

(2) Aramid and cotton blended flame retardant fabric Similarly, in order to reduce costs and achieve multi-functional needs, aramid and cotton fiber are blended with a certain proportion to obtain flame retardant fabrics. In the study of aramid and cotton fiber blending, the blending ratio of aramid and cotton is often 80/20, 50/50, 20/80, and the continuation time, smoldering time and damage length of these three blended fabrics meet the requirements of GB8965-88 before and after washing, and the LOI value of the limiting oxygen index is also greater than the 28 standard with flame retardant requirements. As the aramid content increases, so does the LOI value. Among them, 80/20 fabric has excellent heat resistance and flame retardancy, and can meet the national flame retardant clothing requirements without flame retardant finishing; 50/50 and 20/80 blended fabrics need to be flame retardant and finished by Proban to meet the flame retardant standards.

(3) Aramid and flame retardant viscose fiber blended flame retardant fabric Flame retardant viscose is a kind of silicate-containing fiber toxic fiber, its physical and mechanical properties are similar to ordinary viscose fiber, and can be processed into various textiles. Aramid and flame retardant viscose blend fabric has soft feel, good fluffiness, drape, moisture absorption and air permeability, high strength, wear resistance, good cloth finish, color fastness and charring in case of fire and other excellent characteristics, which can meet the quality requirements of high- and medium-grade flame retardant clothing and decorative fabrics.

(4) Aramid and ramie blended flame retardant fabric using aramid fiber as the core yarn, friction spinning technology is applied to cover ramie fiber around it to obtain ramie/aramid core yarn. In addition, ramie yarn treated with alkali is selected and combined with aramid filament, and composite yarn is obtained without twisting. After weaving into fabrics, appropriate flame retardant treatment can meet certain flame retardant requirements.

2.2 Aramid anti-static functional textiles

Ordinary textile fibers, especially chemical fibers, are easy to generate and accumulate a large amount of static electricity, and electrostatic discharge sparks in flammable and explosive environments as ignition sources often cause explosion disasters. At the same time, most textile fibers are flammable or flammable materials, the limiting oxygen index is generally between 17~25, far lower than the minimum value of self-extinguishing in the air 27, once the fabric encounters the ignition source will burn rapidly. In order to ensure the safety of operators in many fields involving explosion hazards, such as fire fighting, petrochemical, ordnance, mining, etc., it is necessary to replace flammable and static ordinary fabrics with fabrics with both flame retardant and anti-static properties.

When aramid and conductive fibers are blended and interwoven to form a new type of fabric, due to the compatibility and complementarity of the flame retardant performance and electrical dissipation performance of the fabric, the fabric has obtained the long-lasting protection function of flame retardant and anti-static. The latest aramid product developed by DuPont, Aracon, uses magnetron sputtering technology to sputter metal on the surface of aramid fibers to form a thin film, which not only has an antistatic effect, but also shields high-frequency radiation and signals.

2.3 Development of aramid fiber impregnated fabrics

Kevlar fiber impregnated fabric is a new type of high-grade insulation material used in large motors, and aramid fiber fabric adopts a process of two dips and two rolling. First, part of the glue is rolled out after the fabric is impregnated, so that the glue is immersed in the gap of the fabric, and then rolled to immerse the glue into all the hairs inside the fiber; Then the second dipping is carried out, this time mainly covering the surface of the fabric, so that the surface of the fabric is covered with a certain amount of glue, and the second pressing is to make the glue coating evenly everywhere, and then dry in the oven.

Due to the excellent performance, aramid fiber can be used as the insulation material for the motor to make the heat resistance level as high as 180 °C or more; If the mica can withstand a high temperature of 180 °C, but due to the weight, the weight of the motor increases, and the mica is brittle and the source is not sufficient. Compared with motors made of mica insulation material with the same power, motors made of aramid fiber can save 28% of copper, 15% of steel and 10% of silicon steel sheets. Composites made of aramid are 30% lighter and twice as hard as fiberglass composites made by the same method.

2.4 Application of para-aramid on bulletproof clothing

Para-aramid fiber fabrics have the highest expansion strength, high elastic modulus and low specific density, which can absorb and disperse the energy of the bullet impact to other fibers of the woven fabric, avoiding “blunt injury”, so the protective effect is remarkable. At the same time, the lightweight of aramid body armor and helmet effectively improves the rapid response ability and protection ability of the army.

2.5 Research on aramid/carbon fiber hybrid woven reinforced concrete

Through the theoretical analysis and practical test of aramid/carbon fiber fabric reinforced concrete, it can be seen that the function of fiber fabric reinforced concrete is very obvious, especially the use of these two high-performance fibers as the reinforcing material of the load-bearing structure, which can replace the role of steel bars, and the weight is reduced by 41.8% compared with reinforced concrete, which is conducive to improving the seismic performance of the building and the foundation treatment of the structure, so as to obtain high economic and bearing benefits. However, how to facilitate the construction of fiber fabrics, and at the same time easy to be mastered by ordinary construction workers, still need to be studied in more depth.

2.6 Textiles for aramid tires

Due to the excellent performance of aramid, the mechanical properties of the prepared tire cord at high temperature are basically not affected by temperature, and the internal consumption is low, the heat generation is small and the life is long under the action of alternating stress. Aramid can reduce the volume and mass of tire reinforcement materials, while minimizing material and energy consumption, and raising some of the limits to new heights. In addition, aramid does not have rust problems, and can replace all the metals in the tire (including bead wire), save rubber material, so that the tire performance to achieve light weight, reduced rolling resistance, fuel saving and dimensional stability, good uniformity, and no flat point phenomenon, high-speed performance, traction and braking performance is the best, wear resistance, puncture resistance is good, waste tires are easy to deal with.

2.7 Aramid non-weft functional textiles

Also used for bulletproof, puncture non-woven cloth and plain cloth have better elastic resistance. Because in the manufacturing process of non-weft fabric, aramid fiber material has been fully developed, fixed by adhesive, and there is no interlacing point between fibers, when subjected to the impact of the projectile, it is conducive to the dispersion of energy, more fibers can participate, and energy can be absorbed in a larger area, so its elastic resistance is better.

The areal density of aramid non-woven cloth and the mass fraction of matrix resin are important factors affecting the elastic performance of its laminate. When the weftless fabric has a small areal density and a lower matrix resin mass fraction, the elastic performance of its laminate will also be better.

2.8 Aramid / carbon fiber non-woven fabric

Aramid / carbon fiber non-woven fabric is prepared by puncture method, its oxygen barrier index LOI is 38~42, and the fire temperature reaches 700 °C. Mainly used for fireproof heat insulation interlining, high temperature dust filtering, decorative interlining, fire splash covering cloth, etc.

2.9 Aramid/armor steel composite sheet

Aramid fiber reinforced resin matrix composites have the characteristics of light weight, high strength, good elastic performance and excellent flameproof effect. Adding aramid fiber composite board to armor steel can improve its knock resistance, and the structure of the material will affect the shock wave attenuation effect of the material. When the materials are arranged in the order in which the wave impedance decreases, the shock wave is attenuated more effectively. Materials with multi-layer structure have a better attenuation effect than double-layer structural materials, and protective materials with excellent knock resistance can be obtained.

Third, the development direction of aramid fiber

According to the “Twelfth Five-Year Plan”, during this period, China’s thousand-ton para-aramid production technology will achieve breakthroughs and will shift to a rapid growth period, thereby driving the rapid development of related industries. Focusing on strategic emerging industries, major projects of national economic construction, national defense industry, material industry structure upgrading, etc., China Chemical Fiber Industry Association conducts key analysis on the demand for major downstream application fields, product self-sufficiency rate, and main varieties that need to be imported. In the next 10 years, domestic automobiles, communications, high-speed railways, aviation and protection and other fields will develop rapidly, and the demand for paralamid will be strong; At the same time, the industrial transfer of foreign downstream processing enterprises to China will also stimulate the growth of domestic demand for para-aramid. In 2015, the domestic demand for para-aramid will exceed 10,000 tons, and in 2020, it will exceed 20,000 tons, of which the domestic demand is predicted to be 2,000 tons of para-aramid filament universal type, 1,000 tons of high-strength type, and 2,000 tons of high-strength model; para-aramid staple fiber 2000 tons; 3000 tons of para-aramid pulp. In addition, by 2015, the domestic supply of para-aramid will reach 50%, and in 2020, it will reach 80%.

Fourth, aramid fiber product development

According to the characteristics of aramid special fabrics, the following products can be developed:

1. Bulletproof camouflage clothing, stab-proof vest, bulletproof and impact-resistant helmet, tank coverall, bulletproof shield, racing suit, etc.;

2. Cut-proof clothing, explosion-proof clothing, anti-stabbing clothing, anti-cutting bags, etc.;

3. Hood, gloves, socks, etc

4. Labor protection supplies for children and the elderly

5. Pajamas

6. Aramid non-woven fabric

7. Public safety equipment, transportation safety packaging, and protective devices for vehicles and aircraft

In order to answer your doubts, the above is what we have organized about Function Fabric, hope it can help you.

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