Polyimides applications

A number of interesting observations can be made based on the data presented in Table 4. Storing even in nitrogen affects adhesion negatively in the case where no APS is used at the interface (samples 2 and 2a). In the no APS case, the adhesion appears to be a function of the F% concentration on the surface prior to polyimide application, as is shown in Fig. 3. 

Amine-anhydride reactions, equilibrium, 115 Anhydride-amine reaction, equilibrium, 115 Anhydride hydrolysis, polyimides, 58,60r,61/62 Aqueous ion extraction, kinetic model, 438-440 Aromatic polyimides applications, 67 properties, 26 structures, 27,28/ use as dielectric materials, 26... 

Polyimide Applications. Polyimides are used where their lubricity, low coefficient of thermal expansion, heat resistance, and radiation resistance are required. Typical uses include bearings and piston rings in jet engines, appliances, office equipment, com-... 

This polymerization is carried out in the two stages indicated above precisely because of the insolubility and infusibility of the final product. The first-stage polyamide, structure [IX], is prepared in polar solvents and at relatively low temperatures, say, 70°C or less. The intermediate is then introduced to the intended application-for example, a coating or lamination-then the second-stage cyclization is carried out at temperatures in the range 150-300°C. Note the formation of five-membered rings in the formation of the polyimide, structure [X], and also that the proportion of acid to amine groups is 2 1 for reaction (5.II). 

Miscellaneous Applications. Ben2otrifluoride derivatives have been incorporated into polymers for different appHcations. 2,4-Dichloroben2otrifluoride or 2,3,5,6-tetrafluoroben2otrifluoride [651-80-9] have been condensed with bisphenol A [80-05-7] to give ben2otrifluoride aryl ether semipermeable gas membranes (336,337). 3,5-Diaminoben2otrifluoride [368-53-6] and aromatic dianhydrides form polyimide resins for high temperature composites (qv) and adhesives (qv), as well as in the electronics industry (338,339). 

Uses. Pyromellitic dianhydride imparts heat stabUity in applications where it is used. Its relatively high price limits its use to these applications. The principal commercial use is as a raw material for polyimide resins (see POLYIMIDES). These polypyromellitimides are condensation polymers of the dianhydride and aromatic diamines such as 4, -oxydianifine ... 

Du Pont produces this polymer under the trade names of Kapton, Pyrafin, Vespel, and Pyre-ML. The trade names refer to polyimides used for film, semiconductor coatings, mol ding applications, and wire enamel, respectively. They have exceUent thermal, electrical, and physical properties. 

D. Wilson, H. D. Stenzenberger, and P. M. Hergenrother, Polyimides—Chemistry and Applications, Blackie and Sons Ltd., Glasgow, 1990. 

For convenience of application it is usual to utilise the two-stage preparation shown above. Initially the soluble polymer (I) is formed which is then converted into the insoluble thermally stable polyimide (II) Figure 18.35). Suitable solvents for the high molecular weight prepolymer (I) include dimethylformamide and dimethylacetamide. 

Polyimides and related materials have also been used in a number of specialist applications. Polyimide foams (Skybond by Monsanto) have been used for the sound deadening of jet engines. Polyimide fibres have been produced by Rhone-Poulenc (Kermel) and by Upjohn. 

Newer fabrics, not in common use but in development, test, and field trials, are described for higher temperature applications by Reference [50]. Application to 400°F—2100°F are potentially available using ceramic fibers Nextel 312 , laminated membrane of expanded PTFE on a substrate, polyimid fiber P-84, Ryton polyphenylene sulfide, and woven fiberglass. The heat and acid resistance of these new materials... 

Epoxy based primer systems remain the best suited for the corrosion protection of magnesium. Cathodic epoxy electrophoretic paints , chromate inhibited epoxy-polyamide primers and high temperature stoving epoxy sealers are used to provide protection up to 180°C. For higher temperature applications up to 300°C, epoxy silicone or polyimide based systems can be used. 

Since the end of the 1970s, the polyimides have been introduced for the production of electronic components mainly for the passivation. But more and more they are interesting for the integrated circuits and multichip modulus fabrications. Processability and dielectric and thermomechanical properties are the most attractive features of these materials for the electronic31 and electro-optical applications.32... 

Alicyclic dianhydrides are interesting for electronic applications. The polyimides obtained from them are colorless with high transparency in the visible range, exhibit low birefringence,125 and have a low dielectric constant.126 The reactivity of the polycyclic aliphatic dianhydride has been investigated. For example, bicyclo-[2,2,2]-oct-7-ene tetracarboxylic dianhydride reacts quickly with an aromatic amine because the bicyclo-imide is less strained than the corresponding dianhydride.127... 

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