Imide groups polyamides/imides

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. 

Polyamide-imides may also be produced by reacting a diacid chloride with an excess of diamine to produce a low molecular mass polyamide with amine end groups. This may then be chain extended by reaction with pyromellitic dianhydride to produce imide linkages. Alternatively the dianhydride, diamine and diacid chloride may be reacted all together. 

In this paper we use dielectric measurements to calculate the polarizability of absorbed water in a series of aromatic polyimides and polyamide-imides. In the relatively non-polar polyimides, the absorbed water has a dipole moment close to that of free water (/i - 1.88 Debyes). This value drops to less than 0.4/x for polyamide-imides. The decrease may be attributed to hydrogen-bonded water in the very polar polyamide-imides. In addition, the "group" dipole moment for amide is calculated and found to be greater than the dipole moment of free water. 

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. 

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. 

The thermoplastic variety of polyimides with enhanced melt processabihty is obtained by combining the basic imide stmcture with more flexible aromatic groups such as aromatic ethers or amides. Polyamide-imides are produced by condensing trimellitic anhydrides with aromatic diamines, while polyetherimides are made by the reaction between bisphenol A, 4,4 -methylene dianiline, and 3-nitrophthalic anhydride. 

Aramide fibers, according to a definition issued by the US Federal Trade Commission, consist of long-chained synthetic polyamides in which at least 85 % of the amide groups are bound directly to two aromatic rings. DIN specifies that such aramides can also contain imide groups. The worldwide production volume of aramide fibers is 40,000 t/a. 

The engineering polymers that have already reached maturity consist of the Nylons (PA), polycarbonate (PC), acetal (POM), polyesters (PBT and PET) and Noryl (PPO). Their relative price is aroxmd 3. Including very novel polymers, a prestigious high priced group consists of the advanced engineering polymers (high performance) polysulfone (PSU), polyphenylene-sulfide (PPS), fluoroethylenes (PTFE and its derivatives), polyamide-imide (PAI), polyether-imide (PEI), polyethersulfone (PES), polyether-ether-ketone (PEEK), aromatic polyesters and polyamides, polyarylates and liquid-crystal-polymers (LCP). 

Polyimides (PI), Polyamide-lmide (PAI), Polyether-lmide (PEI) The typical imide group consists of... 

The structure of EPDM grafted onto polyamide 66 was analysed by FTIR spectroscopy. Evidence indicated the presence of cyclic imide groups, derived from grafted maleic anhydride groupings (229). 

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 ... 

A polyamide-imide (PAI) features alternating imide and amide substructure sequences, an example being a pyromellitimide and amide, with a general structure as indicated below, where A1 is an alkyl group. The IR spectrum of a polyamide-imide is similar to that of a polyimide, except that amide grouping provides an additional carbonyl stretching vibration at around 1670 cm ... 

A number of polymers containing unsaturated imide side groups susceptible to cure by a thermal treatment (maleimide, nadimide, tetrahydrophthalimide), have been described [247,248]. The reactive side groups are generally introduced in this case by means of modified condensation monomers bearing reactive imide groups (Scheme 48). This approach has been applied for the preparation of cross-linkable aromatic polyamides and polyesters [248,249]. 

Method 3.6 Determination of Amino Groups in Aromatic Polyamides, Polyimides and Polyamides-imides. Potassium Hydroxide Fusion Gas Chromatography [158, 159]... 

Imide groups formed in polyamide 6 (polyhexanamide) hydrolyse faster than in polyamide 11 (polyundecanamide) and polyamide 12 (polydodecanamide). The role of water in the photo-oxidation of aliphatic amides is limited to a reaction with the imide groups [1321]. 

Determination of Amide and Imide Groups in Polyamides, Poiyimides, and Poiyamides/lmides... 

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