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Kevlar (para-aramid) [2] is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora.Developed by Stephanie Kwolek at DuPont in 1965, [3] [2] [4] the high-strength material was first used commercially in the early 1970s as a replacement for steel in racing tires.
In 1973, DuPont was the first company to introduce a para-aramid fiber, calling it Kevlar; this remains one of the best-known [citation needed] para-aramids and/or aramids. In 1978, Akzo introduced a similar fiber with roughly the same chemical structure calling it Twaron .
In contrast, Kevlar derives its strength from strong bonding between relatively short molecules. The weak bonding between olefin molecules allows local thermal excitations to disrupt the crystalline order of a given chain piece-by-piece, giving it much poorer heat resistance than other high-strength fibers.
Modern aircraft powered by jet engines usually have them fitted with a sort of armour in the form of an aramid composite kevlar bandage around the fan casing or debris containment walls built into the casing of their gas turbine engines to prevent injuries or airframe damage should the fan, compressor, or turbine blades break free. [1]
The samples demonstrated similar depth, but the neat Kevlar displayed more yarn-pullout and yarn splaying. Observers found that the STF-Kevlar was able to withstand the stab test better than the neat Kevlar. Later on, in a spike impactor stab test, the STF-Kevlar demonstrated significantly better results than the neat Kevlar.
Molecular structure of Kevlar Molecular structure of the LCP Vectran [5]. Liquid crystallinity in polymers may occur either by dissolving a polymer in a solvent (lyotropic liquid-crystal polymers) or by heating a polymer above its glass or melting transition point (thermotropic liquid-crystal polymers). [6]
Nomex is an example of a meta variant of the aramids (Kevlar is a para aramid). Unlike Kevlar, Nomex strands cannot align during filament polymerization and have less strength: its ultimate tensile strength is 340 MPa (49,000 psi). [2] However, it has excellent thermal, chemical, and radiation resistance for a polymer material.
Kevlar is a registered trademark for a para-aramid synthetic fiber developed at DuPont in 1965 [1] and used commercially from the early 1970s onwards. On February 3, 2009, DuPont filed suit against Kolon for "theft of trade secrets and confidential information" relating to its product, Heracron.