What is aramid
The full name of aramid fiber is "aromatic polyamide fiber", which refers to a long-chain synthetic polyamide fiber with more than 85% of the amide bonds directly connected to the benzene ring. The amide bonds connected are aromatic rings or derivatives of aromatic rings, and are flame retardant. , high temperature resistance, high strength, high modulus, insulation and other outstanding properties, it is a new type of special polymer material. Currently, there are two types of aramid fibers on the market that have achieved widespread commercial application and production, namely meta-aramid fiber and para-aramid fiber.
Meta-aramid has excellent thermal stability, flame retardancy, electrical insulation, chemical stability and radiation resistance. The full name of meta-aramid is "polyisophthalyl-m-phenylenediamine" (MPIA) fiber, which is an organic polymer fiber synthesized from isophthaloyl chloride and m-phenylenediamine. Because the amide bond is connected at positions 1 and 3 of the two benzene rings, it is also called aramid 1313. Meta-aramid has long-term thermal stability, which is its most important characteristic. It can be used at high temperatures of 200°C for a long time without aging, and has excellent dimensional stability. Meta-aramid is intrinsically flame retardant, with a limiting oxygen index (LOI) >28%. It will not spontaneously ignite or melt in the air, nor will it produce droplets, and will self-extinguish upon leaving the flame. Meta-aramid has excellent electrical insulation, and the insulating paper made from it has a breakdown voltage of up to 20kV/mm. Meta-aramid has excellent corrosion resistance and radiation resistance. In addition, meta-aramid 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. Together with carbon fiber and high-strength and high-module polyethylene, it is known as the world's three major high-performance fibers. The full name of para-aramid is "poly-paraphenylene terephthalamide" (PPTA) fiber. It is an organic polymer fiber synthesized from terephthaloyl chloride and para-phenylenediamine. Due to the amide bond connecting two benzene rings, The No. 1 and No. 4 positions are also called aramid 1414. The tensile strength of para-aramid fiber is 6 times that of steel wire, and 2 to 3 times that of glass fiber and high-strength nylon industrial yarn; its tensile modulus is 2 to 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 steel wire. Para-aramid has good impact resistance, corrosion resistance and fatigue resistance, and is known as "ballistic fiber". The heat resistance of para-aramid is higher than that of meta-aramid. It can still maintain its original strength after hundreds of hours at a high temperature of 200℃, and it will not decompose or melt at a high temperature of 560℃. In terms of environmental protection, the stable structure of para-aramid fiber and its resistance to degradation also determines its difficulty in later recycling and environmental impact.