Aramid Fibers and Fabrics Information
Short for aromatic polyamide fibers, aramid fibers are any of a series of high-strength, heat-resistant synthetic polymer fibers. Chemically, they are a combination of long chainlike molecules linked by strong hydrogen bonds. They are an extension of the research that led to the creation of nylon and their unique properties make them useful in a diverse array of applications.
The first aromatic polyamides were produced in the early 1960s, with the first commercial product being a meta-aramid fiber from DuPont called Nomex. Thanks to its strength and heat resistance combined with tactile characteristics that were close to normal textiles, Nomex was quickly adopted for a number of uses including protective apparel, insulation and more.
Today, tens of thousands of tons of meta-aramid and para-aramid fibers are manufactured each year by multiple manufacturers under several brand names, and they are used in products across dozens of industries.
By chemistry, there are numerous types of aramid fibers. The Federal Trade Commission defines an aramid fiber as any manufactured fiber with a long-chain synthetic polyamide that has a minimum of 85% of its amide linkages attached directly to two aromatic rings. Classifying aramid fibers by commercially branded products, their types include or have included:
· New Star
Thanks to their chemical composition of long chainlike molecules that are linked by strong hydrogen bonds, high-performance aramid fibers can transfer mechanical stress with high efficiency while maintaining a low molecular weight. The hydrogen bonds are aligned, for the most part, along the fiber axis, which gives them remarkable strength and flexibility.
Aramid fibers are distinctly different than many other synthetic fibers thanks to their overall toughness. They are renowned for their high tensile strength, seemingly untearable without the use of incredible force. However, aside from their resistance to abrasion and piercing, they also have high resistance to organic solvents and are extremely fire resistant. They have no melting point and only begin to degrade at extremely high temperatures, and also have low flammability. Nomex starts to decompose at around 350 degrees C while Kevlar and other para-aramids do not degrade until above 500 degrees C. The fibers also display excellent performance characteristics in extremely freezing temperatures and are nonconductive.
Aramid fibers have a strength per unit of weight several times that of steel, aluminum and E-glass, and are lighter than fiberglass. The fibers are not totally indestructible, however, as they are sensitive to UV rays, acids and salts.
Their unique properties of high strength, low weight, and flame and solvent resistance have made them useful in an incredible array of product applications. Just some of these applications include:
· ballistic applications like bulletproof body armor in the form of vests and helmets
· flame-resistant and heat protective clothing and helmets for firefighters, pilots, race car drivers and others
· asbestos replacement
· tires and mechanical rubber goods reinforcement
· support ropes and cables
· optical fiber cables
· sporting goods like tennis strings, skis, snowboards, golf club shafts and hockey sticks
· musical equipment like drumheads, wood instrument reeds and loudspeaker diaphragms
· marine applications like boat hulls (large boats and small vessels like canoes and kayaks) and sail cloth
· helicopter rotor blades
· solid rocket motors
· compressed natural gas tanks
· aircraft panels
· lightweight bicycles
· filter bags and other filtration devices
· automobile parts like hoses and v-belts
Chemically, aramid fibers are simply long chainlike molecules composed of oxygen, carbon, hydrogen and nitrogen. How they are made is a more complex, synthetic process. Aramids are prepared into the form of a polymer by the reaction between an amine group and a carboxylic acid halide group. These stiff polymer molecules have a strong crystal orientation and close interaction between polymer chains thanks to their strong hydrogen bonds.
Aramids are made into fiber form by spinning the dissolved polymer into a solid fiber form. During the production process, they can be manufactured into a fiber, chopped fiber, powder or pulp form. The manufacturing methods include hand lay-up, vacuum bagging, vacuum infusion, resin transfer molding (RTM), RTM light, press molding, filament winding and pultrusion.
Each of the commercially branded aramid fibers bring slightly different performance characteristics to the products they are used in. For example, Kevlar has outstanding strength-to-weight properties and an extremely high tolerance to heat, which has made it one of the most popular aramid fibers for bulletproof vests. Nomex, while not as strong as Kevlar and para-aramid variants, has excellent thermal, chemical and radiation resistance making it a popular fiber for protective firefighter apparel and hazardous material suits. While manufacturers must consider the specific properties and cost of each aramid fiber option, the choice is already made for consumers who simply buy a finished product and benefit from the optimally chosen aramid.
Since the breakthrough in production that brought the world the meta-aramid Nomex in the 1960s and on to early para-aramids like Kevlar in the 1970s and beyond, the production of aramid fibers has been among of the most significant advancements in modern raw material technology in history. Offering characteristics that are superior to anything nature can provide, the fibers are revolutionizing what is possible for consumer products and advanced machines to achieve. Thanks to aramid fibers, a vest can stop a bullet or save a soldier from an explosion. Firefighters, pilots and racecar drivers can walk away from intense blazes. Clean up workers can survive exposure to high levels of radiation. Boats, automobiles and airplanes can be built stronger, lighter and with better fuel efficiency.
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Carbon fiber and carbon fiber cloth consist of bulk, chopped fibers, continuous strands or woven cloth forms of carbon or graphite. Carbon and graphite are used in reinforcing composites as well as other specialized electrical and thermal applications.
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Cordage, rope and webbing are made of many natural and/or synthetic fibers that are twisted and/or braided or woven into a length.
Fibers and Filaments
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Glass Fibers and Fiberglass Cloth
Glass fibers and fiberglass cloth consist of bulk, chopped fibers or continuous strands of glass. Glass fibers and fiberglass cloth is used in reinforcing plastics and composites as well as other specialized electrical and thermal applications.
Industrial fabrics consist of woven or non-woven cloth made from natural or synthetic materials.
Mineral Wool and Glass Wool
Mineral wool and glass wool are made from slag, rock, glasses or minerals that have been melted and spun into fibers.
Natural Fibers and Fabrics
Natural fibers and fabrics consist of bulk fibers, yarns, or woven cloth manufactured from plant materials such as cotton, wool, linen (flax), sisal, jute, hemp, or silk.
Nonwovens are fiber-based products that are formed into mats of randomly-oriented fibers, felt, needlepunched cloth, spunbond, or meltblown structures.
Specialty Fibers, Fabrics, and Textiles
Specialty fibers, fabrics and textiles are based upon a unique composition, weave, or technology, and are designed for specialized applications.
Synthetic Fibers and Fabrics
Synthetic fibers and synthetic fabrics consist of bulk fibers, yarns, woven cloth or other textile products manufactured from polymer-based materials such as polyamide (nylon), polyester, aramid, or other spun thermoplastics.