polyimide

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polyimide

[¦päl·ē′ī‚mīd]
(chemical engineering)
A group of polymers that contain a repeating imide group (‒CONHCO‒). Aromatic polyimides are noted for their resistance to high temperatures, wear, and corrosion.

Polyimide

 

a polymer containing cyclic imide groups in their main or side chains:

Aromatic linear polyimides with imide rings in the main chain have acquired practical importance because of their valuable physicochemical properties, which remain unchanged over long periods in a wide range of temperatures (from –270° to + 300°C).

Polyimides are solid, heat-resistant, incombustible substances of predominantly amorphous structure, with molecular weight w = 50,000–150,000 and density 1.35–1.48 g/cm3 (20°C). Most polyimides do not dissolve in organic solvents, are inert to the action of oils and remain virtually unchanged under the action of dilute acids but are hydrolyzed by alkalies and superheated steam. Polyimides are resistant to ozone, γ-rays, and fast electrons and neutrons and are very resistant to heat. The most industrially valuable polyimides are the polypyromellitimides:

They do not soften even at the onset of thermal decomposition (500°-520°C) and can withstand a tension of 50 meganewtons per sq m (MN/m2), or 500 kilograms-force per sq cm (kgf/cm2), at 300°C; their tensile strength at 20°C is 180 MN/m2, or 1,800 kgf/cm2, and their temperature for prolonged use is 250° –300°C.

Polyimides are produced mainly by polycondensation of tet-racarboxylic acids and their derivatives, mainly dianhydrides (most often those of pyromellitic acid and 3, 4, 3′, 4′-benzo-phenonetetracarboxylic acid), with diamines (for example, bis[4-aminophenyl] ether and m-phenylenediamine) in one or two stages. Macromolecular soluble polyamic acids are usually produced first. Films and fibers are formed from these materials and then undergo heat treatment. Polyimides are also worked by pressure molding. Polyimides are used to make monolithic items, electrical insulation films, wire and cable insulation, binders for reinforced plastics, adhesives, plastics, foamed plastics, and fibers; they are used in aviation and space technology.

In the USSR, polyimides are used in making PAK-1 varnish, PM film, DFO molding composition, STP-1 glass-fiber-reinforced plastics, SP-1 adhesive, and Arimid fiber; they are used in the USA to produce Kapton H film, Vespel, and M–33.

REFERENCES

See references under .

IA. S. VYGODSKII

polyimide

Pronounced "poly-ih-mid." A type of plastic (a synthetic polymeric resin) originally developed by DuPont that is very durable, easy to machine and can handle very high temperatures. Polyimide is also highly insulative and does not contaminate its surroundings (does not outgas). Vespel and Kapton are examples of polyimide products from DuPont. See tape automated bonding.
References in periodicals archive ?
Fully aromatic polyimides are well known to exhibit high thermal stability and resistance to solvents, and as a consequence, they are typically unable to be processed with conventional thermoplastic equipment.
In this article, the semicrystalline polyimides containing bridged linkages were synthesized using different monomers, and their properties were characterized.
Evonik Jayhawk Fine Chemicals Corporation and Nexam Chemical AB have begun a joint-marketing program, whereby Evonik's JAYHAWK dianhydrides and Nexam Chemical's NEXIMID crosslinkers will be offered in a coordinated effort to the growing polyimide market sector.
Drawn from a December 2003 international symposium of the same name as the book, 27 papers explore recent research developments in the material science of polyimides and other high temperature polymers.
Note that multifunctional epoxy has a decomposition temperature of 295[degrees]C (563[degrees]F) and polyimide materials, with much more stable molecular structures, have decomposition temperatures of 361[degrees]C and 385[degrees]C respectively, while the much lower Tg crosslinked olefin product has a decomposition temperature of 395[degrees]C.
Polyamide-imides, as the name suggests, derive a synergy of properties from both polyamides and polyimides. High strength, melt processability, exceptional heat resistance, and broad chemical resistance are some.
It is well known that polyimide (PI) is an attractive high-performance material with excellent thermal stability, solvent resistance, and electric properties [28], The applications of PI polymer focus on electrics, optical waveguide, liquid crystal, aero/aviation, membrane separation, and so on [29, 30].
A comparison of tensile strength is shown in figure 2 for composites A (TS-A) and B (TS-B), which are thermoset polyimides, and composites C (TP-C) and D (TP-D), which are engineering thermoplastics.
The resulting polyoxazolidone resins could be lower-cost alternatives to polyimides in composite applications with maximum operating temperatures in the range of 390 F.
Polyimides belong to the class of high-performance polymers.
* High-heat thermoplastic polyimides are moldable, extrudable.