What is Polyamide Fiber?
Polyamides are polymers, which contain recurring amide groups as essential parts of the main polymer chains. Polyamides were the first synthetic polymer developed through research by Wallace Carothers at DuPont laboratories. Naturally occurring polyamides include the protein fibers, e.g., silk and wool fibers. Synthetic polyamide fibers form one of the most important of all classes of textile fiber, which we know today as nylon fiber. Nylon is one of the most common polymers used as a textile fiber.
Besides, Nylon is now known by a more generic name, polyamide, because it is made out of amide-based chemicals. Polyamides are available in many forms, including compliant textiles and rigid, durable resistant materials. In textiles, there are several forms of nylon depending upon chemical synthesis such as nylon 4, 6, 6.6, 6.10, 6.12, 8, 10 and 11 types. The most common nylon are 6 and 6.6 types. Nylon 6 (nylon Z type) and nylon 66 (nylon XY type) are the two most manufactured polyamides, which are commonly used in a wide range of applications from apparels, ropes, carpets, tyre cords to technical textile applications.
Microscopic View of Polyamide Fiber
Properties of Polyamide Fiber
The physical and mechanical properties of polyamide fibers depend on their peculiar molecular structure. These fibers exhibit a great breaking length (40–50 km), high elasticity (complete recovery amounts to 35–40% of the total elongation); the recovery of nylon 66 is equal to 100% after stretching it by approximately 8%. The high abrasion resistance of polyamide fibers is an extremely valuable property in practical textile use. The abrasion resistance of polyamide fibers excels that of natural and other man-made synthetic fibers. The behavior of polyamide fibers in water is somewhat specific and distinctive. Swelling of polyamide fibers in water is not considerable and their strength in the wet state is very slightly reduced (by about 5–10%). At a relative humidity of 65%, these fibers absorb 3.5–4% of moisture content. This is probably due to the low content of hydrophilic chemical groups. Polyamides belong to thermoplastic polymers and melt without decomposition: nylon 6 at 215°C, nylon 66 at 255°C, nylon 7 at 225°C and nylon 11 at 186–187°C. As compared with nylon 6, nylon 66 melts at a considerably higher temperature, which is due to its greater crystallinity and to the larger number of hydrogen bonds between amide chemical groups.
Common properties of polyamide fiber are given below:
- Absorbency: Polyamide is not absorbent, and most of the moisture remains on the surface of the fabric material. The material is generally smooth, so it dries quickly as the water either runs off easily or stays on the surface for the air to evaporate it naturally.
- Resilience: It possesses excellent elasticity and resilience. In spun and knitted polyamide products, however, resilience and elasticity are reduced slightly.
- Strength: Polyamide is one of the strongest fibers (aramid and glass are stronger, though), and it does not deteriorate with time or usage.
- Draping: It has excellent draping qualities regardless of the weight of the textile fabric.
- Insulating: Polyamide is warm and often used in outdoor clothing and apparel.
- Abrasion: Because it has high abrasion resistance, it can withstand excessive rubbing, wringing and scraping without breaking or any loss of strength or durability.
- Lightweight: The degree of its lightness varies based upon the denier of the fiber but it is still considered to be lightweight and comfortable.
- Resistance: Polyamide is resistant to most chemicals, mildew, perspiration and insect damage.
- Susceptible: Polyamide will melt if an iron is too hot; therefore, the irons should be set on their lowest temperature settings. Cold, concentrated solutions of mineral acids, such as hydrochloric, sulphuric and nitric acids, can decompose polyamide. The low absorption rate of polyamides can be problematic because it can make wearers feel clammy in warm, humid environments. Also of note: white nylon can yellow in sunlight exposure.
Polyamide Fiber Manufacturing Process from Coal and Petroleum By-products
- Chemical Treatment: Coal and petroleum by-products are treated with hexamethylene diamine and adipic acid chemicals.
- Water Evaporation: The mixture is heated to evaporate water, producing concentrated polyamide chemical
- Caprolactam Formation: This salt is treated with sulphuric acid, creating cyclohexanone oxime (known as caprolactam chemical).
- Polymerization: Caprolactam is heated in a steel drum to produce linear super polymers (giant molecular chains). These are mixed with titanium dioxide powder.
- Filtration and Solidification: The solution is filtered through slots to remove impurities. It ends up on revolving wheels and is sprayed with cold water, solidifying into milky-white, opaque ribbons.
- Flake Formation: The ribbons are chipped into flakes and placed into a hopper, where they are melted completely.
- Sand Filtration: The melted flakes are passed through a sand filter to remove any remaining small impurities.
- Melt Spinning: The purified melt is extruded through a spinneret and solidified in cold air streams.
- Conditioning: A conditioner is added to moisten the fibers, helping them stick together easily.
- Drawing and Twisting: A soft twist is applied, and the fibers are drawn to 2–7 times their original length, enhancing strength, elasticity and durability.
- Final Products: Staple Fiber and Continuous Filament yarns.
Finishes of Polyamide Fibers
- Anti-Static: to reduce the electrostatic build-up effectively.
- Calendering: to create patterns in fabric e.g., moiré via embossing which gives a permanent decorative finish.
- Heat Set: uses the thermoplastic property of a material to produce a permanent shape e.g., pleated fabric.
- Moulding: using thermoplasticity polyamide can be thermo-formable using heat and pressure to produce shaped fabrics and structures.
- Nylonizing: carried out on nylon 8 and used to coat other forms of nylon to increase their water absorbency.
- Water Repellency: for added protection against liquid penetration.
Variations of Polyamide Fibers
- Monofilament: 5, 10, 20, 40 and 60 denier are used for hosiery. Trade Names – include Astroturf, Cantrece, Crepset, Crepset anti-cling (carbon added), Firestone (tyres) and Monosheer hosiery.
- Multifilament: ranging from 20—210 denier, including Antron™, Cordura™, Cumuloft™, Enkalon™ and Ultron™ fibers.
- Trilobal: includes Antron™, Enkaloft™ and Ultron™, which are used in the carpet industry for unique lustre, dryness, and print definition. The three lobes help hide dirt and hold the dirt to enable effective vacuum cleaning, so preventing dirt or grit being ground in the back cloth which would weaken and eventually break the yarns. Fibers are crimped for increased resilience and strength.
- High-Tenacity: a thicker skin and aligning the molecules via stretching produces high-tenacity materials used in car tyres and technical textiles.
- Crimped/Looped: includes Crepset, mechanical crimp, Taslan and Cantrece. These use different types of nylon e.g. 6.6 with 6.10 (bi-component fiber); each type sets at a different rate in the melt-spun stage of production, which causes the fiber to corkscrew; the higher temperatures produce more spirals naturally.
- Delustre: can vary from bright to dull via the use of titanium dioxide, barium sulphate, zinc oxide or zinc sulphate compounds.
- Optical Whitener: added to the polymer in the vat before extrusion process.
- Conductive: carbon particles added to the polymer in the vat before extrusion help transport current, which greatly reduces static electricity buildup.
- Microfiber: provides fabric with breathable, quick-drying, softer, lightweight and better draping performance.
Fabrics of Polyamide Fiber
A large proportion of man-made fabrics on the market are sold with just the fiber content. However, there are a few fabrics that are either 100% (or some other percentage) of polyamide. Fabrics include fur, lace, net, organdie, organza and ripstop textiles.
Blends of Polyamide
- Cotton—polyamide: will add strength, smoothness, lightness, dust resistance and crease-resistance – whereas the cotton will provide softness and absorption. However, the balance between the two has to be correct; otherwise, the cotton will shrink, causing the polyamide to pucker or distort.
- Wool: will provide added drape, body, absorbency and warmth and the polyamide adds elasticity and shape retention qualities.
- Silk: improves the hand and moisture absorption properties of the combination and polyamide improves the shape retention, elasticity and tensile strength of the fabric.
- Viscose: offers improved drape and moisture absorption and polyamide offers strength, especially when wet, and creases less easily.
- Acetate: provides a luxurious hand and polyamide adds strength. However, because neither material absorbs moisture very well, the wearer will feel clammy in warm and humid conditions.
Industrial Uses of Polyamide Fiber
Polyamide is used in clothes and sportswear, hosiery, swimwear, outdoor jackets, ski wear, netting and underwear. It is also used for soft furnishings, such as bedspreads, carpets, decorative curtains, cushions and shower curtains fabrics. In the industrial world, it is used for military uniforms, filters, fishing nets, parachutes, flak jackets, tyres, life jackets, kites, sails, umbrellas, luggage and instrument strings.
Conclusion
Polyamide, commonly known as nylon, is a versatile and high-performance polymer built from repeating amide linkages, occurring naturally in protein fibers and produced synthetically in major types such as nylon 6 and 6.6. Its unique combination of strength, elasticity, abrasion resistance, and lightweight nature makes it suitable for a wide range of applications, from everyday apparel to technical and industrial textiles.
References
[1] Ashford, B. (2016). Fibers to Fabrics.
[2] Kolanjikombil, M. (2018). The substrates: fibers, Yarn and Fabric. Woodhead Publishing.
[3] Sinclair, R. (2014). Textiles and fashion: Materials, Design and Technology. Woodhead Pub Limited.
[4] Jindal, A. J. R. (2023). Textile raw materials. Abhishek Publications.
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. Mr. Kiron is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
