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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.
High strength and stiffness, less permeable to gases, almost reflects light completely: Food packaging, transparent covering over paper, reflector for rollsigns and solar cooking stoves Neoprene: Polychloroprene: Chemically inert: Manufacturing gaskets, corrosion resistant coatings, waterproof seat covers, substitute for corks and latex: Nylon ...
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.
Although liquid–gas transitions have a higher heat of transformation than solid–liquid transitions, liquid→gas phase changes are impractical for thermal storage because large volumes or high pressures are required to store the materials in their gas phase. Solid–solid phase changes are typically very slow and have a relatively low heat ...
Note that for gases in usual conditions, heat transfer by advection (caused by convection or turbulence for instance) is the dominant mechanism compared to conduction. This table shows thermal conductivity in SI units of watts per metre-kelvin (W·m −1 ·K −1 ).
The study, which was published in the journal Chemosphere, detailed how high levels of these flame retardants were found in kitchen utensils, food containers, trays used to hold meat and even toys ...
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.
Dense gases such as xenon and dichlorodifluoromethane have low thermal conductivity. An exception, sulfur hexafluoride, a dense gas, has a relatively high thermal conductivity due to its high heat capacity. Argon and krypton, gases denser than air, are often used in insulated glazing (double paned windows) to improve their insulation ...