Application fields and application progress of para-aramid

Bulletproof vests and bulletproof helmets made of para-aramid have been equipped in the US military for a long time. According to statistics from military experts, more than 75% of casualties on the battlefield are caused by low-speed, medium-speed stray bullets or bomb fragments, and casualties caused by direct bullet hits do not exceed 25%. Therefore, people pay more and more attention to the use of high-performance bulletproof vests. Early hard bulletproof vests were made of special steel plates, super-hard aluminum alloys, etc. The bulletproof vests were heavy and not flexible. Later, they were gradually replaced by soft bulletproof vests. The so-called soft bulletproof vests refer to those made of high-performance organic fibers such as para-aramid. The requirements for fiber materials in bulletproof vests are high strength, high modulus and certain toughness. High strength and high modulus make the fiber have excellent impact resistance, and high toughness enables the fiber to effectively absorb the kinetic energy of the bullet during deformation. Although carbon fiber also has high strength and modulus, its toughness is poor and its weavability is also poor, so it cannot be used as a fabric for bulletproof vests. The bulletproof vests woven from para-aramid are light in weight, comfortable, flexible and easy to move. They have been equipped by the armies of many countries in the world. In addition, Kevlar fiber braids are also widely used in helicopter pilot and gunner seats to absorb the impact force generated during collisions to protect pilots.

Para-aramid is also widely used in all-non-metallic self-supporting optical cables (ADSS). The high strength of aramid is enough to withstand the load of ADSS in use, and the high modulus makes the fiber only deform slightly when it is under load, so that the diameter change of the optical cable can be limited to a very small range. The excellent dimensional stability of para-aramid will greatly increase the service life of the optical cable in overhead optical cables, and its low density can reduce the difficulty of installation. At the same time, the good insulation and non-magnetic properties of para-aramid will not affect signal transmission. Combining the above advantages, para-aramid is very suitable for use in ADSS.

Para-aramid has been used in offshore engineering. Previously, offshore projects were mostly equipped with steel cables and wire ropes. However, in deeper waters, steel cables and wire ropes are prone to breakage due to their heavy weight, and another alternative material needs to be found. Para-aramid has low density, high specific strength and specific modulus, and has good solvent resistance and low elongation. Therefore, the cable made of multiple strands of para-aramid has high strength, and even if it breaks, it will not rebound and hurt people.

Due to its excellent mechanical properties, para-aramid is a very ideal composite reinforcement. The engine casings of the "Trident" missiles equipped by the United States and the SS-24 and SS-25 missiles of the Soviet Union are all made of Kevlar fiber-reinforced epoxy resin composite materials. The casings of many aerospace engines also use Kevlar fiber-reinforced composite materials.

Para-aramid is also used in data cables of electronic products. It can provide effective structural support for cables, protect internal wires, and improve the overall tensile strength and bending resistance of cables. Due to the excellent chemical resistance and heat resistance of para-aramid, vacuum hoses reinforced by para-aramid will have very good application prospects in the field of oil and gas extraction in the future. In addition, para-aramid can be processed into filaments, staple fibers, chopped fibers and pulp, which have different application fields.