Polyimide (abbreviated PI) is polymer of imide monomers. Polyimides have been in mass production since 1955. With their high heat-resistance, polyimides enjoy diverse applications in end uses demanding rugged organic materials, e.g. high temperature fuel cells, displays, and various military roles.
Properties
Thermosetting polyimides are known for thermal stability, good chemical resistance, excellent mechanical properties, and characteristic orange/yellow color. Thermoset polyimides exhibit very low creep and high tensile strength. These properties are maintained during continuous use to temperatures of up to 452 °C and for short excursions, as high as 704 °C. Polyimides are inherently resistant to flame combustion and do not usually need to be mixed with flame retardants. Typical polyimide parts are not affected by commonly used solvents and oils - including hydrocarbons, esters, ethers, alcohols and freons. They also resist weak acids but are not recommended for use in environments that contain alkalis or inorganic acids.
Applications
Polyimide materials are lightweight, flexible, resistant to heat and chemicals. Therefore, they are used in the electronics industry for flexible cables, as an insulating film on magnet wire and for medical tubing. In coal-fired power plants, waste incinerators or cement plants, polyimide fibres are used to filter hot gases. In this application, a polyimide needle felt separates dust and particulate matter from the exhaust gas. Polyimide is also the most common material used for the reverse osmotic film in purification of water, or the concentration of dilute materials from water, such as maple syrup production. Multi-layer insulation used on spacecraft is usually made of polyimide coated with thin layers of aluminum. The gold-like material often seen on the outside of spacecraft is actually single aluminized polyimide, with the single layer of aluminum facing in. The yellowish-brown polyimide gives the surface its gold-like color.
End uses
Aerospace: Jet engines and compressor parts, seals, impellers for aircraft, aircraft engines (sandwich constructions with titanium alloys), insulation of the spacecraft and the astronauts space suits against radiation, heat or cold exposure, radomes.
Electrical and electronics industry: insulating, electronic connectors, bobbins, wire and cable jacketing, the base material for printed circuit boards.
Automotive and machinery industry: piston rings, valve seats, wheels, bearings, sliding and guiding elements, pads, carburetor body.
Other: Fibers for refractory protective suits.
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