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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.
Excellent thermal stability at temperature extremes, water repellency, chemical stability and resistance to petroleum products have made Kevlar KM2 an indispensable asset to the military personnel who use it every day." [1] "Kevlar KM2 fiber is a transversely isotropic material. Its tensile stress–strain response in the axial direction is ...
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 .
Although the tensile strength is similar to Kevlar, Vectran still tends to experience tensile fractures when exposed to significant stress.The wispy, hair-like fibers tend to fray, to easily acquire dirt, and to readily entangle in hook-and-loop fasteners, from which they must sometimes then be cut or (when possible) torn. [2]
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.
p-Phenylenediamine (PPD) is an organic compound with the formula C 6 H 4 (NH 2) 2.This derivative of aniline is a white solid, but samples can darken due to air oxidation. [1] It is mainly used as a component of engineering polymers and composites like kevlar.
The specific strength is a material's (or muscle's) strength (force per unit area at failure) divided by its density.It is also known as the strength-to-weight ratio or strength/weight ratio or strength-to-mass ratio.
The 500-million download threshold for free applications has been established to maintain the list's manageability and focus on the most widely distributed apps. It's worth noting that many of the applications in this list are distributed pre-installed on top-selling Android devices [ 2 ] and may be considered bloatware by some people because ...