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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.
World capacity of para-aramid production was estimated at 41,000 t (40,000 long tons; 45,000 short tons) per year in 2002 and increases each year by 5–10%. [12] In 2007 this means a total production capacity of around 55,000 tonnes per year. [citation needed]
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 ...
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.
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.
A call for a next generation plate, to stop even greater velocity threats than the ESAPI plate was issued by the U.S. Army in 2008. [5] The X Threat Small Arms Protective Insert plates are specifically allowed scalar or flexible systems, and asked for better coverage, with less than a pound of additional weight.
gr/yard: Grains per yard of yarn. Gr/yard is a direct measure of linear density, but is rarely used in the modern textile industry. ECC or NeC or Ne (English Cotton Count): The number of 840 yd lengths per pound. ECC is an indirect measure of linear density. It is the number of hanks of skein material that weighs 1 lb.