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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.
Same as the small molecular liquid crystal, liquid crystal polymers also have different mesophases. The mesogen cores of the polymers will aggregate into different mesophases: nematics, cholesterics, smectics and compounds with highly polar end groups. [10] More information about the mesophases can be found on liquid crystal page.
Although typically "doping" conductive polymers involves oxidizing or reducing the material, conductive organic polymers associated with a protic solvent may also be "self-doped." Undoped conjugated polymers are semiconductors or insulators. In such compounds, the energy gap can be > 2 eV, which is too great for thermally activated conduction.
Zylon (IUPAC name: poly(p-phenylene-2,6-benzobisoxazole)) is a trademarked name for a range of thermoset liquid-crystalline polyoxazole. This synthetic polymer material was invented and developed by SRI International in the 1980s and manufactured by Toyobo. [2] In generic usage, the fiber is referred to as PBO. [3]
Conductive agents are used to ensure electrodes have good charge and discharge performance. Usually, a certain amount of conductive material is added during the production of the pole piece , and the micro current is collected between the active material and the current collector to reduce the micro current.
PBI Gold fabric was born, consisting of 40% PBI/60% para-aramid. Previous to this, combinations of Nomex, leather, and Kevlar materials were used in the US. 1983 – A unique production plant goes on-line and PBI fibers become commercially available. 1990s – Short-cut PBI fibers are introduced for use in automotive braking systems.
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.
Tether properties and materials are dependent on the application. However, there are some common properties. To achieve maximum performance and low cost, tethers would need to be made of materials with the combination of high strength or electrical conductivity and low density. All space tethers are susceptible to space debris or micrometeoroids.