What is Aramid Fiber?
The full name of aramid fiber is "aromatic polyamide fiber", which refers to the long-chain synthetic polyamide fiber whose amide bond is directly connected to the benzene ring. The amide bond is connected to the aromatic ring or derivatives of the aromatic ring. It is a new type of special polymer material with outstanding properties such as high temperature resistance, high strength, high modulus, and insulation. At present, there are two kinds of aramid fibers on the market that have achieved a wide range of commercial applications and production, namely meta-aramid and para-aramid.
Meta-aramid has excellent thermal stability, flame retardancy, electrical insulation, chemical stability and radiation resistance. The full name of meta-aramid fiber is "poly-m-phenylene isophthalamide" (MPIA) fiber, which is an organic polymer fiber synthesized from isophthaloyl chloride and m-phenylene diamine. Meta-aramid has long-term thermal stability, which is its most important characteristic. It can be used at a high temperature of 200°C for a long time without aging, and has excellent dimensional stability. Meta-aramid has intrinsic flame retardancy, its limiting oxygen index (LOI) is >28%, it will not spontaneously ignite, melt, or produce molten droplets in the air, and it will extinguish itself when it leaves the flame. Meta-aramid fiber has excellent electrical insulation, and the breakdown voltage of insulating paper made of it can reach 20kV/mm; meta-aramid fiber has excellent corrosion resistance and radiation resistance. In addition, meta-aramid fiber also has low rigidity and high elongation, and can be processed by conventional textile machinery.
Para-aramid has excellent properties such as high specific strength, high specific modulus, high temperature resistance and flame retardancy, and is known as the world's three high-performance fibers together with carbon fiber and high-strength high-modulus polyethylene. The tensile strength of para-aramid is 6 times that of steel wire, 2~3 times that of glass fiber and high-strength nylon industrial yarn; the tensile modulus is 2~3 times that of steel wire and glass fiber, and 10 times that of high-strength nylon industrial yarn ; Its density is only about 1/5 of that of steel wire. Para-aramid has good impact resistance, corrosion resistance and fatigue resistance, and is known as "bulletproof fiber". The heat resistance of para-aramid is higher than that of meta-aramid. After hundreds of hours at a high temperature of 200°C, it can still maintain its original strength, and it will not decompose or melt at a high temperature of 560°C. In terms of environmental protection, para-aramid has a stable structure and is not easy to degrade, which also determines that it is difficult to recycle and deal with and affect the environment in the later stage.
Aeronautics
Aramid fiber has low density, high strength, and good corrosion resistance. It can be used to manufacture rocket engine casings for missiles, broadband wave-transmitting materials for fuselages, main wings, and empennages of aircraft and spacecraft, and structural components that can withstand impact forces. Aramid fiber can also be used to make secondary structural materials for large aircraft, such as cabin doors, windows, wings, fairing body surfaces, etc., and can be used to make ceilings and warehouse walls in the aircraft to reduce its weight.
The multi-layer honeycomb structure board prepared by impregnating aramid cloth with epoxy resin to form aramid prepreg and directly bonding with honeycomb or foam structure has outstanding impact resistance and electromagnetic wave permeability. The super-hybrid composite laminate formed by overlapping and hot-pressing aramid fiber, thin aluminum plate, and epoxy non-woven fabric has extremely high specific modulus and specific strength, and its anti-fatigue life is 100 to 1000 times that of aluminum alloy plate. It can be used in aircraft fuselage and other parts. The resin-based reinforced composite material prepared by aramid fiber is applied to the aircraft passenger body, which can greatly reduce the total weight of the aircraft.
Their main advantage is that they are very strong and lightweight, which can reduce the overall weight of the aircraft, increase safety, improve fuel consumption efficiency, and reduce air pollution. In addition, aramid and its composite materials are resistant to corrosion, which can ensure the safety of aircraft in harsh environments without problems such as water accumulation, freezing or corrosion.
The future development trend of aramid fiber and its composite materials in aerostructure design is also very impressive. Due to the many advantages of aramid and its composite materials in the design of aerostructures, they can almost replace steel and aluminum materials in terms of efficiency and safety, and can achieve more flexibility in the structural design and manufacturing process. In addition, the weight of aramid and its composite materials is also decreasing, which will make the aircraft lighter and more maneuverable in the air.
Military Field
Aramid composite materials can be used to manufacture missile solid rocket motor casings, pressure vessels, spacecraft cockpits, submarines, bulletproof armored vehicles, bulletproof cash transport vehicles, bulletproof panels, bulletproof helmets, body armor, etc.
Aramid fibers, carbon fibers, and ultra-high molecular weight polyethylene fibers are called the three high-performance fibers. They are widely used in national defense and civilian industries, and are strategic materials for a strong country and a strong army. The products are mainly used in the fields of optical fiber and cable, rope ribbon, skeleton material, composite material, friction sealing material, textile and bulletproof protection, and the standard configuration is bulletproof vest.
Bulletproof vests and bulletproof helmets made of aramid fibers can replace old-fashioned nylon vests and tank helmets. Adding an appropriate amount of aramid to bulletproof vests and helmets can not only make them small in size and light in weight, but also increase their bulletproof performance by 40%. . The soft bulletproof vest made of high-grade bulletproof aramid non-woven fabric and high-performance polyethylene film has better bulletproof performance and heat resistance than ultra-high molecular weight polyethylene fiber. Aramid fibers can also be compounded with other materials (such as metals, ceramics, etc.) to make various high-strength, impact-resistant explosion-proof tanks, bullet-proof shields and bullet-proof armor plates, etc. In addition, the aramid fiber fabric is bonded to the inner wall of the structure, which can effectively absorb the blast wave and prevent the damage of the shrapnel to the human body.
Electronic and Electrical Field
Due to the relatively late start of research on aramid materials in my country, the technology has developed rapidly. The currently developed satellite APSTAR-2R uses a honeycomb interlayer as the reflective surface of the antenna. The inner and outer skins of the antenna use para-aramid materials, and the interposition uses honeycomb aramid. In the manufacturing process of the aircraft radome, para-aramid is used to take advantage of the good wave-transmitting performance of this material and the low expansion coefficient, so the frequency of the reflector can meet the dual requirements of its own structure and function. ESA has developed a two-color sub-type reflector with a diameter of 1.1m. It uses a meta-honeycomb structure in the sandwich structure and uses aramid material as the skin. The epoxy resin temperature of this structure can reach 25°C and the dielectric constant is 3.46. The loss factor is 0.013, the reflection loss of the transmission link of this kind of reflector is only 0.3dB, and the transmission signal loss is 0.5dB.
The laminated substrate made of aramid fiber and epoxy, phenolic, polyimide and other resins has a high matching degree of linear expansion coefficient with ceramics, and will not cause cracking under the action of thermal expansion and contraction, and can be used to make surface mount technology The special printed circuit board in it is conducive to the miniaturization and light weight of electronic equipment. Utilizing the characteristics of high strength and high temperature resistance of aramid fiber, it is used as a "tension member" in the optical fiber, which can protect the small and fragile optical fiber from elongation and deformation when it is subjected to tension, and will not affect the transmission of light. The composite product of aramid fiber and carbon fiber has good processability and semiconductor properties, and can withstand high temperature. It is mostly used to make materials for reducing electric fields in high-voltage devices. After being impregnated with insulating varnish, aramid paper has good insulation properties, and combined with natural mica sheet, it is used as insulation material for heat-resistant motors.
Other Fields
Aramid fibers contain a large number of benzene rings in their molecules, which have good chemical stability, corrosion resistance, high specific strength, light and strong, and can be used to manufacture cables for seagoing vessels and deep oil wells. Utilize the high temperature resistance and fatigue resistance of aramid fiber to make high-grade rackets, fishing rods, sleds, skis, ski poles, bows and arrows, rowing boats, golf clubs, etc., and can also be used to make mountaineering shoes with harsh sports conditions Boots, boxing gloves, racing helmets, racing car bodies, etc. Since asbestos is a serious hazard to the human respiratory tract, aramid fibers can be used instead of asbestos to make reinforced rubber sealing plates and other seals, which are used for the liners and rings of automobile brakes.
With more and more types of textile equipment, the production technology of the textile industry has also been developed more and more. Aramid fabric is a fiber type that is developed early, widely used, large in production and fast in development. Aramid fabric is a high-performance fiber fabric with the characteristics of heat resistance, chemical corrosion resistance, radiation resistance, flame retardancy, and high strength. Therefore, it has a wide range of applications in industry, military, fire protection, aerospace and other fields.
Industry: Aramid fabric can be used to make high-temperature and corrosion-resistant products such as high-temperature filter materials, valve covers, and sealing gaskets. In addition, in textile, petrochemical, electronics, shipbuilding and other industries, aramid cloth is also a commonly used material.
Military aspects: Aramid fabrics are mainly used in the production of protective equipment such as bulletproof vests, stab-proof vests, and helmets. Because aramid cloth has excellent strength and heat resistance, it can effectively protect soldiers from bullets, shells and other attacks.
In terms of fire protection: aramid fabric can be used as fire protection belt, fire protection curtain and other materials. Because aramid fabric itself has flame retardant properties, it can effectively prevent fire after a fire occurs.
Aerospace: Aramid fabrics can be used to make high-strength, high-temperature-resistant products such as aircraft seats, space suits, and parachutes. Aramid cloth can also be used as satellite sunshade materials, rocket heat insulation materials, etc.
