Introduction to Aramid

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Introduction to Aramid Fibers: Aramid fibers, whose full name is “polyphenylene terephthalamide”, are also known as Aramid fiber in English. Brands such as Twaron produced by Teijin and Kevlar produced by DuPont are examples of such fibers. They represent a new type of high-tech synthetic fiber with excellent properties including ultra-high strength, high modulus, as well as resistance to high temperatures, acids, and alkalis. Their strength is 5 to 6 times that of steel wire, their modulus is 2 to 3 times that of steel wire or glass fiber, and their toughness is twice that of steel wire. Moreover, their weight is only about 1/5 of that of steel wire. At a temperature of 560 degrees, they neither decompose nor melt. It has good insulation and aging resistance, as well as a long service life. The discovery of aramid is considered a very important historical milestone in the field of materials science. Production background edit: Since asbestos was recognized as a strong carcinogen, many developed countries around the world have begun to ban asbestos and its products. Countries such as the United States and Japan have successively developed various series of non-asbestos gasket materials, which are now available in the global market. As it becomes increasingly integrated with the international environment. Non-asbestos sealing materials are being recognized and adopted by various industrial sectors in the country. For reasons of environmental protection and safe production, the industrial use of non-asbestos gaskets will become increasingly widespread. Sealing gaskets that use non-asbestos fibers as reinforcing materials and rubber as the elastic matrix are generally referred to as non-asbestos fiber rubber gaskets, or alternatively as asbestos-free gaskets or asbestos substitute gaskets. Its main reinforcing materials include asbestos-substitute fibers, inorganic fibers, carbon/graphite fibers, etc. Current Development Status Edit: Aramid fibers were developed in the late 1960s; initially, they were little known as materials for space exploration and as important strategic resources. After the end of the Cold War, aramid gradually became known to the public after being widely used in civilian applications as a high-tech fiber material. The full name of aramid is “aromatic polyamide fiber,” and it is a type of new synthetic fiber designed for special purposes. There are two types of aramids that are most useful in practice: one is the meta-aramid fiber, whose molecular chains are arranged in a zigzag pattern; in China, this is referred to as Aramid 1313 ； The first is the para-aramid fiber with molecular chains arranged in a linear pattern, which is referred to in China as Aramid 1414. Globally, the production capacity of global meta-aramid (1313) is 32,000 tons, with a basic balance between supply and demand. In terms of domestic supply and demand, China’s demand for meta-aramid is around 10,000 tons, while the total domestic production capacity is 8,600 tons, indicating a significant shortage in capacity. As the market leader in China’s meta-aramid industry, Taihe New Materials holds over 60% of the market share, with its gross margin remaining steadily above 35%. The global production capacity for para-aramid is approximately 65,000 tons, while the global demand for para-aramid in 2011 was around 53,000 tons. The main producers of para-aramid in the world are DuPont in the United States and Teijin in Japan, with production capacities of 28,600 tons and 28,450 tons respectively, thus almost monopolizing the international market. At present, China’s annual demand for para-aramid exceeds 5,000 tons, all of which must be imported, with the current price at 200,000 yuan per ton. With environmental protection campaigns in Europe and the United States aiming to ban the use of asbestos, aramid pulp fibers have seen rapid development, gradually replacing asbestos as the main material for brake pads, clutch plates, and gaskets. In addition, it is also widely used in other industrial fields, such as fiber optic protection, high-temperature filter bags, automotive hoses, tires, sound wave damping fabrics, power transmission belts, conveyor belts, transfer printing blankets, and rubber shoe soles ； In the field of personal protection, aramid can be used to manufacture bulletproof vests, bulletproof helmets, bulletproof armor, as well as firefighting suits, firefighting masks, military and police training uniforms, and cut-resistant gloves ； In the civilian sector, aramid can be used to make flame-retardant interiors and fabrics for airplanes, cars, and high-speed trains; it can also be utilized to produce fire-resistant blankets, escape ropes, flame-retardant curtains, bedcovers, pajamas, tablecloths, aprons, and microwave oven gloves. Aramid can also be turned into aramid paper, which is used for insulation in motors, transformers, and electronic devices. It can further be processed into honeycomb structure materials, which are used for secondary components in airplanes, yachts, high-speed trains, and bullet trains. https://imgsa.baidu.com/baike/s%3D220/sign=85d67f2a6a600c33f479d9ca2a4d5134/4a36acaf2edda3cc926c041e00e93901213f9200.jpg Properties of aramid fibers: 1. Good mechanical properties – Meta-aramid is a flexible polymer with a higher breaking strength than ordinary polyester, cotton, nylon, etc. It has a high elongation rate, a soft feel, and is easy to spin into short fibers and filaments of various diameters and lengths. Using standard textile machinery, these can be turned into yarns used to create fabrics and non-woven materials; after further processing, they can meet the requirements for protective clothing in different applications. 2. Excellent flame-retardant and heat-resistant properties: The limiting oxygen index (LOI) of meta-aramid is greater than 28, so it does not continue to burn once it is removed from the flame. The flame-retardant properties of Newstar® meta-aramid are determined by its chemical structure; therefore, it is a permanently flame-retardant fiber whose flame-retardancy does not diminish or disappear due to prolonged use or repeated washing. Nystar® meta-aramid possesses excellent thermal stability; it can be used continuously at 205°C, and still maintains high strength at temperatures above 205°C. Nystar® meta-aramid has a high decomposition temperature; it does not melt or drip at high temperatures, and carbonization begins only when the temperature exceeds 370°C. 3. Stable chemical properties: Meta-aramid possesses excellent resistance to most chemicals; it can withstand most high-concentration inorganic acids, and it has good resistance to alkalis at room temperature. 4. Radiation resistance: Meta-aramid possesses excellent radiation resistance. For example, under prolonged exposure to ultraviolet rays at 1.2×10⁻² W/in² and γ-rays at 1.72×10⁸ rads, its intensity remains unchanged. 5. Durability: Thanks to the excellent abrasion and chemical resistance of meta-aramid, even after 100 washes, the tear strength of fabrics processed with Newstar® meta-aramid remains at over 85% of their original strength. The temperature resistance of para-aramid is higher than that of meta-aramid. Its continuous service temperature range is from -196 °C to 204 °C; it does not decompose or melt even at a high temperature of 560 °C. The most notable characteristics of para-aramid are its high strength and high modulus; its strength is greater than 25 grams/denier, which is 5 to 6 times that of high-quality steel, 3 times that of glass fiber, and 2 times that of high-strength nylon industrial fibers ； The modulus is 2 to 3 times that of high-quality steel or fiberglass, and 10 times that of high-strength nylon industrial yarn. Aramid pulp is obtained by subjecting aramid fibers to surface fibrillation. Its unique surface structure significantly enhances the adhesion of mixtures; therefore, it is ideally suited for use as a reinforcing fiber in friction and sealing products. https://imgsa.baidu.com/baike/s%3D220/sign=421503b770cf3bc7ec00caeee101babd/ac4bd11373f082027fb36e854bfbfbedab641b62.jpg Aramid pulp – a hexagonal specialty fiber; aramid 1414 pulp appears as light-yellow flocculent masses with a fluffy texture. It has abundant fluff, high strength, good dimensional stability, no brittleness, resistance to high temperatures and corrosion, toughness, low shrinkage rate, good wear resistance, and a large surface area. It can combine well with other materials and serves as a reinforcing material. Its moisture content is 8%, the average length is 2–2.5 mm, and the surface area is 8 m2/g. When used as a gasket reinforcement material, it exhibits good rebound and sealing properties. It is harmless to human health and the environment. It can be utilized for sealing media such as water, oil, hydrocarbons, and moderately strong acids and alkalis. The resulting gaskets possess excellent sealing performance as well as resistance to creep and relaxation. It has been found that usually, adding less than 10% pulp is sufficient to obtain products with a strength equivalent to those reinforced with 50–60% asbestos fibers. Used in finished products such as friction enhancers and sealing materials; it can serve as a substitute for asbestos in friction sealing materials, high-performance heat-resistant insulating paper, and reinforced composite materials. Usage: Aramid fibers are important materials for defense and military applications. To meet the demands of modern warfare, bulletproof vests in developed countries such as the United States and the United Kingdom are made of aramid material. The light weight of aramid-based bulletproof vests and helmets enhances the rapid response capabilities and combat effectiveness of military forces. During the Gulf War, American and French aircraft made extensive use of aramid composite materials. Apart from its applications **, it is now widely used as a high-tech fiber material in various sectors of the national economy, such as aerospace, electromechanics, construction, automotive, and sports equipment. In the fields of aviation and aerospace, aramid fibers, with their low weight and high strength, help to save a significant amount of fuel. According to foreign sources, during the launch of spacecraft, reducing the weight by just 1 kilogram can result in cost savings of $1 million. In addition, the rapid advancement of technology is opening up more new civilian applications for aramid. It is reported that aramid products are used in bulletproof vests, helmets, etc. for about 7–8%, while aerospace materials and sports-related materials account for around 40% ； Materials for tire skeletons and conveyor belts account for about 20%, while high-strength ropes and similar materials make up around 13%. The tire industry has also begun to use aramid cords on a large scale in order to reduce weight and rolling resistance. Classification: Aramids are mainly divided into two types: para-aramid fiber (PPTA) and meta-aramid fiber (PMIA). In the field of aramid fiber production, para-aramid fibers are developing the fastest, with production capacity primarily located in Japan, the United States, and Europe. Such as DuPont’s Kevlar fibers in the United States, Teijin’s Twaron and Technora fibers in Japan, and Yantai Taixin New Materials’ Taparan fibers. Among them, both DuPont of the United States and Teijin of Japan have a production capacity of around 30,000 tons each, giving them a monopolistic position in the para-aramid market ； Yantai Taihe New Materials began commercial production of para-aramid in 2011, ranking at the forefront of the country in terms of the commercialization of domestically produced para-aramid. Examples of meta-aramid fibers include DuPont’s Nomex in the United States, Yantai Taihe New Materials’ Tametar, and Teijin’s Conex in Japan. United States: https://imgsa.baidu.com/baike/s%3D220/sign=0c0094918a13632711edc531a18ea056/c8ea15ce36d3d539abdf078e3a87e950342ab098.jpg Tametar’s meta-aramid natural white short fibers – DuPont and Yantai Taihe New Materials are the main competitors in the meta-aramid industry. Both companies are capable of producing industrial-grade natural white short fibers, dyeable short fibers for use in clothing, colored filaments, long filaments, and aramid paper. The performance of their products is relatively similar, with little difference between them; they compete fiercely in areas such as environmental protection, safety measures, industry, electronics, and composite materials. Due to factors such as foreign technological blockades, the production and application of aramids in our country started relatively late. In 2004, Yantai Spandex (now renamed Taihe New Materials) achieved industrial-scale production of meta-aramid, and gradually developed into the world’s second-largest supplier of meta-aramid, thereby significantly promoting the use and development of aramids in the domestic market ； In 2011, Taihe New Materials began commercial production of para-aramid, ranking at the forefront of the country in terms of the commercialization of domestically produced para-aramid. At present, the development of aramid in China has been placed on the agenda. Aramid has been included in the “Catalog of High-Tech Products to be Encouraged for Development” and the “12th Five-Year Plan for the Development of Strategic Emerging Industries”. In the coming years, its development pace is expected to gradually accelerate. Since the late 1960s, various aramids have been developed and produced industrially. There are many types of aramids, and there are various methods for classifying them. The first naming method is based on structure, dividing them into para-aramids, meta-aramids, and ortho-aramids. The monomers for para-aramid are terephthalic acid and p-phenylenediamine; the functional groups on these monomers are in a para configuration, resulting in polymer chains that are quite regular in structure. These materials exhibit good high-temperature resistance, as well as high strength and modulus. The main types of aramid fibers include DuPont’s Kevlar series as a representative example. The monomers of meta-aramid are isophthalic acid and m-phenylenediamine; the functional groups on these monomers are in the meta position. The polymerized chain segments have a serrated structure, offering high heat resistance, although their strength and modulus are slightly lower. Meta-aramids are mainly represented by DuPont’s Nomex series of products. The monomers of ortho-aramid are phthalic acid and o-phenylenediamine, with the functional groups located in an ortho position on the monomers. The main ortho-aramids are represented by DuPont’s Korex product line. The second naming method is also based on structural classification; for example, \"para\" refers to position 14 on the benzene ring, while \"meta\" refers to position 13 on the benzene ring. Aramid 14 denotes a connection at positions 1 and 4 on the benzene ring, whereas Aramid 1414 is the para-aramid mentioned earlier. Aramid 1313, on the other hand, is the meta-aramid mentioned earlier. The third naming method is based on the number of polymerizing monomers; as mentioned earlier, Aramid 14 is also known as Aramid Type I, while Aramid 1414 and Aramid 1313 are referred to as Aramid Type II. Aramid fibers obtained by adding third monomer units such as 4,4’-diaminodiphenyl ether and 5(6)-amino-2-(4-aminophenyl)benzimidazole to common structures like terephthalic acid and terephthalamine, or isophthalic acid and isophthalamine, can be referred to as Aramid Type III. When the monomer of the third unit is a heterocyclic structure, it is also often referred to as heterocyclic aramid