Applications Using Polyamide-imides

Polyamide-imides, due to their high relative cost compared to common engineering plastics such as nylon and polycarbonate, are used when the application conditions require the property benefits of these materials and where lesser polymeric materials would fail. In addition to this, they 

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The Swiss company, WW Fischer, offers PTFE (Teflon PTFE or Hostaflon), PBT (Celanex, Crastin, Ultradur or Valox) or PEEK (Victrex) insulator material options in its 405 series of cylindrical connectors according to the requirements of working temperature and other criteria. PEEK is an expensive polymer which tends to be employed when other materials fail to meet the specification requirements of the application. Other Fischer connector types use polyamide-imide (Torlon) or POM (Celcon, Delrin or Hostaform). Elastomeric seals used by Fischer in conjunction with their connectors are made from acrylonitrile-butadiene rubber (NBR N BUNA) or to MIL-P-25732, fluoroelastomer (FPM VITON), polychloroprene elastomer (CR Neoprene), ethylene-propylene diene elastomer (EPDM) and styrene-ethylene-butadiene-styrene thermoplastic elastomer (TPE-S or TPE-O) where each compound is followed by its trade name. Fischer s Swiss competitor, Lemo, manufactures a similar range of connectors including the Redel types which have a plastic body. 

Polyamide-imide is an engineering plastic used only for specialized and technical applications. 

Linear polymers such as polyamide imides and polyimides are sometimes used as varnishes however, they produce coatings that are not cross-linked. For some applications for which rework and repairs have to be made, cross-linked coatings have a disadvantage. Soluble polymer systems that can be repaired are to be preferred in such cases. 

Progress has also been made in part cooling. Portable and centralized chillers have been developed to cool the part in a minimum time. These closed loop systems use water or water-ethylene glycol combinations as the heat transfer medium. The application of heat transfer principles allows one to computer model the cooling process (35). For the new engineering resins such as polyamide-imide and polyphenylene sulfide, one must use mold heating. The use... 

Both polyamide-imide and polyetherimide have high heat distortion temperature, tensile strength, and modulus. Polyamide-imide is useful from cryogenic temperatures up to 260°C. It is virtually unaffected by aliphatic and aromatic chlorinated and fluorinated hydrocarbons and by most acid and alkali solutions. These polymers are used in high-performance electrical and electronic parts, microwave appliances, and under-the-hood automotive parts. Typical automotive applications include timing gears, rocker arms, electrical connectors, switches, and insulators. 

Another important group are the polyamide imides and polyimides. The substitution of tricarboxylic acid anhydride for dicarboxylic acids during synthesis results in thermally more stable polyamide imides. The polycondensation reaction proceeds in two steps, with the solution of the intermediate polycarboxylic acid used in applications where the final product can be generated by a thermal or baking process. Uses include heat-resistant wire and cable coatings. The basic synthesis of polyamide imides is as follows ... 

This is an engineering plastic designed for thermal/electrical applications requiring high dimensional stability. This material exhibits superior electrical and mechanical performance at continuous use temperatures ranging from -60 to 260 °C. Pyropel HDT polyamide-imide (PAI) produced by Albany International [35] has enhanced properties without the need for post-curing. 

There are currently two popular commercial methods to synthesize polyamide-imides. One is the acid chloride route, and the other is the isocyanate route. The sjmthesis method used will determine and limit to some extent the applications in which the resultant polymer is used. The chemistry of these two methods is outlined helow. 

The polyamide-imide achieved at the end of this process is a high-molecular-weight, fully imidized polymer in solvent with no condensation by-products, since the carbon dioxide gas is easily removed. This convenient form makes it especially beneficial for the manufacturer where the primary end use is wire enamel or another coating application. The solution viscosity is thus controlled by stoichiometry, monofunctional reagents, and polymer solids. The typical polymer sohds level is 35 to 45% and it may be diluted further by the supplier or customer with diluents. 

The endurance benefits and performance characteristics of polyamide-imides qualify them to be an excellent replacement for metal in aerospace components. Inherent nonflammability, chemical resistance, and superb strength at elevated temperatures allow polyamide-imide compounds to be used in metal applications once unheard of for plastic materials. Neat resin, friction and wear, along with glass- and carbon-reinforced polyamide-imide compounds are incorporated in a variety of parts and locations in aerospace vehicles. 

Many high-performance polymer fibres are used in filter media to meet various specific requirements in diverse filtration applications. Filters made from fluoropol-ymer (Polytetrafluoroethylene (PTFE), Polyvinylidene fluoride (PVDF), and Per-fluoroalkoxy alkane (PFA)) fibres, and membranes have inherent, chemical-resistant, and flame-retardant properties, and they are widely employed to filter aggressive chemicals and acids in the manufacture of wafers and microchips in the microelectronics industry. Ethylene ChloroTriFluoroEthylene (E-CTFE) melt blown fabrics have a unique ability to coalesce difficult liquids and can withstand the piranha effect in filtering ozone enriched ultrapure water. Polyphenylene sulfide (PPS) fibres are also chemical resistant, stand high temperature, and are suitable for making baghouse filters. Eilter media made from other high-performance polymer fibres, such as polyamide-imide, polyetherimide (PEI), Polyimide P84 fibre,polyetheretherke-tone, and liquid crystal polymers also appear in the filtration and separation market. 

An all aromatic polyetherimide is made by Du Pont from reaction of pyromellitic dianhydride and 4,4,-oxydianiline and is sold as Kapton. It possesses excellent thermal stability, mechanical characteristics, and electrical properties, as indicated in Table 3. The high heat-deflection temperature of the resin limits its processibility. Kapton is available as general-purpose film and used in applications such as washers and gaskets. Often the resin is not used directly rather, the more tractable polyamide acid intermediate is applied in solution to a surface and then is thermally imidized as the solvent evaporates. 

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