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The History of Kevlar Kevlar is an organic fiber in the aromatic polyamide family It has unique properties and a chemical composition that is its own which distinguishes it from other man-made fibers Kevlar is a combination of high strength high modulus resistance to extension toughness and thermal stability Kevlar has a wide range of uses In the 1960s nylon and polyester opened the door for man-made fibers They were cutting edge fibers in their time but to achieve maximum break strength and initial modulus the polymer molecules needed to be in an extended-chain configuration and almost perfect crystalline packing With flexible-chain molecules such as nylon or polyester this could only be done by mechanically drawn in after spinning This required chain disentanglement and orientation in the solid phase of it Therefore the strength and modulus levels were far lower than theoretically possible values In 1965 scientists at Du Pont discovered a new method of producing an almost perfect polymer chain extension The polymer poly-p-benzamide was found to form liquid crystalline solutions due to the repetitiveness of its molecular backbone The key for the structural requirement for the backbone is para orientation on the benzene ring which allowed for rod-like molecular structures This technology was used when Du Pont released Kevlar aramid fiber in 1971 What is it Kevlar is an aramid a term invented as an abbreviation for aromatic polyamide The chemical composition of Kevlar is poly para-phenyleneterephthalamide and it is more properly known as a para-aramid Aramids belong to the family of nylons Common nylons such as nylon 6 do not have very good structural properties so the para-aramid distinction is important The aramid ring gives Kevlar thermal stability while the para structure gives it high strength and modulus Like nylons Kevlar filaments are made by extruding the precursor through a spinneret The rod form of the para-aramid molecules and the extrusion process make Kevlar fibers anisotropic--they are stronger
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