Aramid
From Free net encyclopedia
Aramid fiber (1961) is a fire-resistant and strong synthetic fiber. It is used in aerospace and military applications, for "bullet-proof" body armor fabric, and as an asbestos substitute. The term is a shortened form of "aromatic polyamide".
A well-known type of aramid fiber (a para-aramid nylon) is commonly known by its DuPont trade name, Kevlar, or Teijin trade name Twaron. It was developed by Stephanie Kwolek. An especially fireproof meta variant is Nomex.
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Aramid fiber characteristics
- sensitive to degradation from ultraviolet radiation
- good resistance to abrasion, organic solvents, and thermal degradation
- sensitive to moisture and salts
- nonconductive
- no melting point
- low flammability
- good fabric integrity at elevated temperatures
- para-aramid fibers such as Kevlar and Twaron, which have a slightly different molecular structure, also provide outstanding strength-to-weight properties, and have high tenacity, and high Young's modulus.
Major industrial uses
- flame-resistant clothing
- protective clothing and helmets
- body armor, although it is being replaced by stronger polyethylene products such as Dyneema.
- composite materials
- asbestos replacement
- hot air filtration fabrics
- tire and mechanical rubber goods reinforcement
- ropes and cables
- sail cloth (not necessarily racing boat sails)
- sporting goods
- drumheads
- speaker woofers
Production
The Federal Trade Commission definition for Aramid fiber is "A manufactured fiber in which the fiber-forming substance is a long-chain synthetic polyamide in which at least 85% of the amide linkages are attached directly to two aromatic rings."
Aramid fiber is produced by spinning a solid fiber from a liquid chemical blend. This relies on a co-solvent with an ionic component (calcium chloride) to occupy the hydrogen bonds of the amide groups, and an organic solvent (N-methyl pyrrolinidone) to dissolve the aromatic polymer; prior to DuPont's (Kwolek's) invention of this process, no practical means of dissolving the polymer was known.
First U.S. Commercial Aramid Fiber Production: 1961, DuPont Company.
Current U.S. Aramid Fiber Producers: INVISTA