What are Aramid Fibers?
Aramid fibers are a type of synthetic fiber known for their exceptional strength, durability, and heat resistance. Aramides belong to the polyamides, but are not melt spun but solution spun and have a completely different property profile than aliphatic polyamides such as PA 6.6 and PA 6. The word Aramid comes from Aromatic Amide — abbreviated as AR.
The fiber-forming substance in this class of fibers is a long-chain synthetic polyamide in which at least 85% of the amide linkages are attached directly to two aromatic rings (-CO-NH-). The two aramid-type fibers, Kevlar and Nomex, are spun as multifilament yarns and may be cut to produce staple by the process developed by E.I. DuPont de Nemours and Co., incorporated.
Aramids are aromatic polyamide variants. They were first brought to the market by DuPont in the early 1960s and sold under the trade name Nomex. Later, a variant called Kevlar was developed. There are now a number of companies that produce aramids throughout the world, such as China, Japan, the Netherlands and the United States.
They are created via the chemical reaction that occurs when an amine group and a carboxylic acid halide group combine, which produces the polymer. During the extrusion process they are gel spun; passed through cool air and then submersed in a bath of cool liquid which grants the fibers great strength. Aramids are five times stronger than steel fiber by weight, and they have a high resistance to heat.
As with polyamides, the main derivatives are found in the petroleum industry and natural gas containing the elements hydrogen, nitrogen, oxygen and carbon and are from the aromatic groups which are joined together with amide or amide linkages.
In this article, I will explain the different types of aramid fibers, their properties, and their common uses in an easy-to-understand way.
Types of Aramid Fibers
There are two main types of aramid fibers: Para-Aramid and Meta-Aramid. The chemical structure of aramides corresponds to the known structure of polyamides. The basic building blocks are terephthalic acid (dicarboxylic acid) or the corresponding dichloride and poly-m-phenylene isophthalamide (meta-type) or poly-p-phenylene isophthalamide (para-type). This results in the aramid types meta and para through a polycondensation reaction with the release of water (H₂O) or hydrochloric acid (HCl).
A. Para-Aramid
Kevlar and Twaron are the most common para-aramid fibers. Para-aramids (Kevlar, Technora, Twaron) are also used for thermal protection, either alone or in blend form. They have the additional property of high degradation temperature, high strength, and stiffness. Para-aramid fibers are manufactured using the air-gap spinning process.
Para-aramid fiber has very high strength with temperature resistance, with 60% strength and modulus retention at 260°C. It does not melt but chars to a black colour. Aramids are resistant to many solvents, have low water absorbency, but are sensitive to ultraviolet (UV).
Para-aramid fiber is used in climbing rope, mooring rope for petrol platforms as well as ropes for marine and transportation, structural panels, car components, exhaust parts, joints, and connectors. Para-aramids form elongated chains, resulting in significantly higher strength.
The commercial production of p-aramid was started in 1970 and it reached almost 40,000 t per annum in 2000. Para-aramids find their applications in bulletproof vests, ropes, composites, and reinforcement. They are high-strength and high-modulus fibers that have revolutionized the technical textile industry and enhanced its market share.
B. Meta-Aramid
Meta-aramids are mostly used in protective clothing and similar applications. The meta-aramid structure is “zig-zag” shaped. The most commonly used fiber, with good textile properties, is the meta-aramid produced with commercial names of Nomex (DuPont) and Conex.
Meta-aramids can resist temperatures of up to 250°C for 1000 hours with only 35% deterioration in strength. At temperatures above 400°C, the aramids form char and survive short exposures up to 700°C. This char is tough and acts as a thermal protective layer, making it a good candidate for fire protection applications.
In 2000, meta-aramid consumption was approximately 17–18,000 tons per year. Meta-aramids are high-temperature-resistant fibers widely used in protective textiles and industrial applications.
Properties of Aramid Fibers
Aramides are characterized by particularly good temperature resistance in continuous use (m-aramide), good chemical resistance, very high strength and a very high modulus of elasticity (p-aramide). Aramid fibers are only slightly UV-resistant because they absorb light, especially in the 300–450 nm range. For outdoor applications, Kevlar must therefore be protected from this radiation. Furthermore, aramid fibers are hygroscopic.
Because of these properties, their suitability for aerospace applications in their pure form is limited. The modulus of elasticity can be further increased by specific thermal after-treatment. Such fibers are called high modulus fibers (Kevlar 49, Twaron HM). Aramides lie between glass and carbon in the KD tensile test.
Typical Properties of Aramid:
- Non-Flammable; it can withstand temperatures over 500°C though some degradation occurs at approximately 540°C – it will ignite with difficulty at 538°C.
- Impact-Resistant and Abrasion-Resistant hence its use in ballistic and stab-resistant products.
- Lightweight.
- Good Organic Salt-Resistance.
- These fibers do not melt, rather they decompose above 380°C.
- High strength (tenacity varies from 4.8 to 5.8 g/den).
- Good modulus.
- Good fabric integrity, particularly at high temperature.
- Inertness to moisture.
- Non-Conductive.
- Usually yellow.
- Acid-Sensitive and Salt-Sensitive.
- Some variants are sensitive to UV radiation.
- Prone to static build up.
- Dye-Resistant; it must be vat dyed before it is extruded.
Finishes of Aramid Fibers
Aramid fibers usually receive special finishes to enhance their performance and comfort in end-use applications. Since aramid is non-conductive, it tends to build up static electricity; therefore, an anti-static finish is essential to prevent static discharge and improve safety, especially in protective and industrial clothing.
Uses of Aramid Fibers
Aramid fibers have revolutionized several industries due to their unique balance of protection and lightweight performance. Aramid fibers are mainly produced as filament yarns, but there are also staple fibers (fiber fineness p-aramid: 0.9–2.5 dtex, m-aramid: 1.7–2.2 dtex (max. 14 dtex); strength p-aramid: 110–275 cN/tex), which can be processed into yarns and nonwovens using the same processes as other staple fibers.
The above combination of properties makes these fibers particularly suited for end use applications such as hot air filtration, protective clothing, fire-fighters’ uniforms, racing car drivers’ suits, laundry presses, bulletproof vests, space and aircraft components, automotive linings for clutch plates and brake pads, gaskets, football pads, sails, hulls, ropes, cords, tire cord, belts, hosing, fiber optic cables and electromechanical cables.
Conclusion
Aramid fibers represent a major advancement in polymer science, reshaping modern materials with unparalleled safety, strength, and performance. From bulletproof armor to aerospace engineering and industrial safety, aramids have become the backbone of innovation in technical textiles. Their balance of lightweight design and high protection ensures they will continue leading the future of advanced materials.
References
[1] Akovali, G. (2012). Advances in polymer coated textiles. Smithers Rapra.
[2] Ashford, B. (2016). Fibers to Fabrics.
[3] Kyulavska, M., Toncheva-Moncheva, N., & Rydz, J. (2017). Biobased polyamide ecomaterials and their susceptibility to biodegradation. In Springer eBooks (pp. 1–34). https://doi.org/10.1007/978-3-319-48281-1_126-1
[4] Jindal, A. J. R. (2023). Textile raw materials. Abhishek Publications.
[5] Ahmad, S., Rasheed, A., & Nawab, Y. (2020). Fibers for technical textiles. In Topics in mining, metallurgy and materials engineering. https://doi.org/10.1007/978-3-030-49224-3
