A fire broke out in a warehouse, and the goods in the warehouse were almost completely burned to ashes. In this pile of rubble, the insurance company personnel were surprised to find that although a large amount of DuPont Kevlar yarn was blackened, it was still intact and had not been burned by the fire. The core of the paper roll is still intact, and the wooden pallet underneath it has also been preserved. The reason is that DuPont Kevlar aramid fiber not only has excellent abrasion resistance and strength, but also has excellent flame retardant and high temperature resistance.
Who is aramid fiber, and how high a temperature can it withstand?
Aramid fiber was born in the late 1960s. It was initially kept secret as a space development material and an important strategic material, adding a lot of mystery. After the end of the Cold War, aramid, as a high-tech fiber material, was widely used in the civilian field and gradually revealed its true colors. The full name of aramid is “aromatic polyamide fiber” (aramid fibers), which is a new type of special-purpose synthetic material. Because the long-chain polymer molecules that make up the fiber contain amide groups, they are both polyamide fibers like nylon. The difference is that in the polymer macromolecules that make up nylon, the amide groups are connected to aliphatic chains, while in the aromatic polyamide fibers, the amide groups are connected to aromatic rings or derivatives of aromatic rings, so this type of fiber is collectively called aromatic. Polyamide fiber, referred to as aramid fiber.
Aramid fiber is mainly divided into two types: para-aramid fiber (PPTA) and meta-aramid fiber (PMIA). Among them, meta-aramid fiber is mainly represented by aramid 1313, which is known as “fire-proof fiber”. Para-position fiber is represented by aramid 1414, which is known as “bulletproof fiber”.
Aramid 1313 was first successfully developed by DuPont in the United States and achieved industrial production in 1967. The most outstanding feature of aramid 1313 is its good high temperature resistance. It can be used for a long time at a high temperature of 220 ℃ without aging. Its electrical and mechanical properties can remain effective for 10 years, and its dimensional stability is excellent. The thermal shrinkage rate is only 1% at around 300°C. It will not shrink, embrittle, soften or melt when exposed to high temperatures of 300°C for a short period of time. It only begins to decompose at strong temperatures above 370°C, and carbonization begins at around 400°C. . Such high thermal stability is unique among current organic heat-resistant fibers.
Special protective clothing made of aramid 1313 does not burn, drip or smoke when exposed to fire, and has excellent fire protection effect. Especially when encountering a sudden high temperature of 900-1500°C, the cloth surface will quickly carbonize and thicken, forming a unique thermal insulation barrier to protect the wearer from escaping. If a small amount of antistatic fiber or aramid 1414 is added, it can effectively prevent the fabric from bursting and avoid hazards such as lightning arcs, electric arcs, static electricity, and flames.
Aramid 1313 colored fiber can be used to make flight suits, chemical defense suits, fire fighting suits and furnace work clothes, welding work clothes, pressure equalizing suits, radiation protection work clothes, chemical protective clothing , high-voltage shielding clothing and other special protective clothing, used in aviation, aerospace, military uniforms, fire protection, petrochemical, electrical, gas, metallurgy, racing and many other fields. In addition, in developed countries, aramid fabrics are also commonly used as hotel textiles, lifesaving passages, household fireproof decorations, ironing board coverings, kitchen gloves, and flame-retardant pajamas to protect the elderly and children.
Almost simultaneously with the invention of aramid 1313, DuPont developed another high-performance synthetic fiber aramid 1414 in the late 1960s, and its product was first launched in 1972. .
Aramid 1414 has a golden yellow appearance and looks like a shiny metal thread. It is actually a liquid crystal polymer composed of rigid long molecules. Because its molecular chains are highly oriented along the length direction and have extremely strong inter-chain bonding forces, it gives the fiber unprecedented high strength, high modulus and high temperature resistance. The discovery of aramid 1414 is considered an important milestone in the development of the materials community.
Aramid 1414 has extremely high strength, which is 5-6 times that of high-quality steel, its modulus is 2-3 times that of steel or glass fiber, and its toughness is 2 times that of steel. , and the weight is only 1/5 of steel. Aramid 1414 has an extremely wide continuous use temperature range and can operate normally for a long time in the range of -196-204°C. The shrinkage rate at 150 ℃ is 0, and it does not decompose or melt at a high temperature of 560 ℃. Its heat resistance is better than that of aromatic 1313, and it has good insulation and corrosion resistance. It has a long life cycle, so it wins the title of “synthesis”. “Steel Wire”.
Aramid 1414 was first used in cutting-edge fields such as national defense and military industry. In order to meet the needs of modern warfare and counter-terrorism, the military and police of the United States, Russia, Britain, Germany, France, Israel, Italy and many other countries have developed body-proof vests, bullet-proof helmets, stab-proof and cutting-proof suits, explosive disposal suits, high-strength parachutes, and bullet-proof vehicles. Aramid 1414 is widely used in body and armor plates. In addition to the military field, aramid 1414 has been widely used as a high-tech fiber material in aerospace, electromechanical, construction, automobiles, marine aquatic products, sporting goods, etc. All aspects of the national economy. </p
