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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.
Liquid-crystal polymers are present in melted/liquid or solid form. [7] In solid form, the main example of lyotropic LCPs is the commercial aramid known as Kevlar . The chemical structure of this aramid consists of linearly substituted aromatic rings linked by amide groups.
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. Due to earlier patents on the production process, Akzo and DuPont ...
It is a white solid at room temperature. It is one of two precursors used to make Kevlar, the other being p-phenylenediamine. TCL is used as a key component in performance polymers and aramid fibers, where it imparts flame resistance, chemical resistance, temperature stability, light weight, and very high strength.
The conductivity of such polymers is the result of several processes. For example, in traditional polymers such as polyethylenes, the valence electrons are bound in sp 3 hybridized covalent bonds. Such "sigma-bonding electrons" have low mobility and do not contribute to the electrical conductivity of the material.
This synthetic method was first used in the lab and later developed into a two step process. In a typical synthesis, starting materials were heated at 270 °C (518 °F) for 1.5 h to form the PBI prepolymer and later the prepolymer was heated at 360 °C (680 °F) for another 1 h to form the final commercial-grade product.
A phase-change material (PCM) is a substance which releases/absorbs sufficient energy at phase transition to provide useful heat or cooling. Generally the transition will be from one of the first two fundamental states of matter - solid and liquid - to the other. The phase transition may also be between non-classical states of matter, such as ...
Liquid armour is a material under research by defense institutions and universities around the world including the United States Army Research Laboratory (ARL). [ 1 ] [ 2 ] [ 3 ] Some of the earliest research in this area was performed at Massachusetts Institute of Technology [ 4 ] and University of Delaware [ 5 ] in 2003.