Polymers polyamide imide

Polydithiazoles Polyoxadiazoles Polyamidines Pyrolyzed polyacrylonitrile Polyvinyl isocyanate ladder polymer Polyamide-imide Polysulfone Decompose at 525°C (977°F) soluble in concentrated sulfuric acid. Decompose at 450-500°C (842-932°F) can be made into fiber or film. Stable to oxidation up to 500°C (932°F) can make flexible elastomer. Stable above 900°C (1625°F) fiber resists abrasion with low tenacity. Soluble polymer that decomposes at 385°C (725°F) prepolymer melts above 405° C (76l.°F). Service temperatures up to 288° C (550°F) amenable to fabrication. Thermoplastic use temperature —102°C (—152°F) to greater than 150° C (302°F) acid and base resistant. 

Polyvinyl isocyanate ladder polymer Polyamide-imide Soluble polymer that decomposes at 385°C (725°F) prepolymer melts above 405°C (761°F). Service temperatures up to 288°C (550°F) amenable to fabrication. 

Polyamide Imides. Polyamide imides (PAIs) are formed from the condensation of trimellitic anhydride and aromatic diamines (33). The polymer is called amide—imide because the polymer chain comprises amide linkages alternating with imide linkages, with the general chemical stmcture ... 

In addition to the commercial aromatic polyamides described above many others have been prepared but these have not achieved commercial viability. There are, however, a number of other commercial polymers that contain amide groups such as the polyamide-imides. The latter materials are discussed in Section 18.14. 

Uses of the polyamide-imides include pumps, valves, gear wheels, accessories for refrigeration plant and electronic components. Interesting materials may be made by blending the polymer with graphite and PTFE. This reduces the coefficient of friction from the already low figure of 0.2 (to steel) to as little as 0.02-0.08. 

The polyetherimides are competitive not only with other high-performance polymers such as the polysulphones and polyketones but also with polyphenylene sulphides, polyarylates, polyamide-imides and the polycarbonates. 

Over the years polymers have been produced suitable for use at progressively higher temperatures. Where this is a requirement, it is usual first to decide whether a rubbery or a rigid material is required. If the former, this has been dealt with by the author elsewhere." If the latter, it is usually convenient to look in turn at polycarbonates, PPO-based materials, polyphenylene sulphides, polysul-phones, polyketones such as PEEK and PEK, polyamide-imides, poly-phthalamides, fluoropolymers, liquid crystal polymers and polyimides. 

Potyimides obtained by reacting pyromellitic dianhydride with aromatic amines can have ladder-like structures, and commercial materials are available which may be used to temperatures in excess of 300°C. They are, however, somewhat difficult to process and modified polymers such as the polyamide-imides are slightly more processable, but with some loss of heat resistance. One disadvantage of polyimides is their limited resistance to hydrolysis, and they may crack in aqueous environments above 100°C. 

Speciality thermoplastics polysulfone (PSU), PPS, fluoroplastics, PEEK, PEI, polyamide imide (PAI), liquid crystal polymers (LCP). 

POLYAMIDE-IMIDE RESINS. An injection-moldable, high-performance engineering thermoplastic, polyamide-imide is the condensation polymer of tnmellitic anhydride and various aromatic diamines with the general structure ... 

Polyimide (PI) caps all other polymers in its temperature range of use (-200 to 260 °C in air short-time even up to 500 °C). Because of its high price, it is used in special cases only, such as space vehicles, nuclear reactors and some electronic parts. Newer developments, related to polyimide, are the polyether imides (e.g. Ultem ), polyester imides and polyamide imides (e.g. Torlon ), all with very good mechanical, thermal and electrical properties and self-extinguishing. 

Includes acetal, granular fluoropolymers, polyamide-imide, polycarbonate, thermoplastic polyester, polyimide, modified polyphenylene oxide, polyphenylene sulfide, polysulfone, polyetherimide and liquid crystal polymers. 

There are also a few common polymers whose accepted names convey relatively little information about the repeating unit structure. The primary examples are polycarbonate, poly(phenylene oxide), polyamide-imides, poly-sulfones, and polyether ketones (see Table 1.3). 

Figure 2. The dipole moment of the absorbed water molecules varies from approximately 1.8 to 0.9 for the polyimides and from 1.1 to 0.7 for the polyamide-imides corresponding to fractional polarizabilities of l.O/i -0.4/x. The low values of p (<0.5p ) as seen in all the amide-imide po ymers and several of the ° polyimides, indicate restricted mobility of the water molecules. In the amide-imide polymers, we believe this is due to increased water-polymer interactions such as hydrogen bonding. Other evidence of hydrogen bonding in polyamide-imides is the water-induced plasticization and Tg lowering frequently observed.

The dipole moment of a selected functional group in the polymer can also be calculated using the Clausius-Mossotti equation. According to Van Krevelan, (15) the "effective polarizability" of a functional group in the polymer is calculated from the measured dielectric constant, the polymer density and the number of moles of that group in the polymer repeat unit. Using the data for the six polyamide-imides listed in Table I, the effective polarizability of the amide group can be determined from... 

Polyamide-imide represents another group of high-temperature engineering polymers, with good dimensional stability, impact and chemical resistance. 

Polyamide Imide Enamels. Aromatic polyamide imide insulations are made from aromatic acids and aromatic diamines. The polyamide imide polymers are primarily present in the form of polyamic acids in the Af-methyIpyrrolidone solutions. During the enameling process the polyamic acids undergo imidization and become essentially fully imidized. Whereas the polyester and polyester imide enamels contain cresylic acids as the major solvent, the polyamide imide enamels are mainly formulated with A/-methylpyrrolidone as solvent. 

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. 

Polyimides (PI) were introduced in 1962 as thermally non-processable Kapton . To improve processability, the main-chain flexibility was enhanced by incorporating segments with higher mobility, viz. polyamide-imide (PAl), polyether-imide (PEI), polyimide-sulfone (PISO), etc. These polymers are characterized by high T = 150-420°C and thermal resistance. They are blended with PPS to enhance its moldability, thermal stability and mechanical performance. 

Polymer Specimens. The materials used in this work were polyimide (PI),polyamide-imide (PAl), polyether-ether-ketone (PEEK), polyphenylene sulfide (PPS) and polyether sulphone (PES). The chemical formulas and physical properties of the specimen polymers are summarized in Table I. The specimen polymers, except PPS, were unfilled while the PPS specimen was filled with glass fiber of Uo wt. %. PAI and PES are amorphous polymer with considerably high glass temperature. The polymers, except PI, can flow at hi temperatures and allow the use of injection molding. 

For polyimides to be useful polymers, they must be processable, which means that they have to be meltable. Melt processability of polyimides can be improved by combining the basic imide structure with more flexible aromatic groups. This can be achieved by the use of diamines that can introduce flexible linkages like aromatic ethers and amides into the backbone. Polyamide-imides (5) are obtained by condensing trimellitio anhydrides and aromatic diamines, while polyetherimides (6) are produced by nitro displacement reaction involving bisphenol A, 4,4 -methylenedianiline, and 3-nitrophthalic anhydride. 

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. 

---