Aromatic polyester-imides

Discuss the chemistry of aromatic polyamide-imides and aromatic polyester-imides. Give examples. 

Aromatic Polyamide-Imides and Aromatic Polyester-Imides... 

Other nitrogen containing polymers which have been subjected to thermal decomposition studies include aromatic polyester imides containing 2,7-bis(4-aminobenzoyloxy) naphthalene groups [16], poly-4-vinylpyridine [17], poljmrethanes [18], polybutyl cyanoacrylate [19], and polypropyl acrylate [20]. 

Aliphatic-aromatic copoly imides, 268 Aliphatic-aromatic polyesters, 18, 19 Aliphatic degradable polyesters, 41 Aliphatic diacids, polyamide synthesis from, 183-184... 

Specialty polymers achieve very high performance and find limited but critical use in aerospace composites, in electronic industries, as membranes for gas and liquid separations, as fire-retardant textile fabrics for firefighters and race-car drivers, and for biomedical applications (as sutures and surgical implants). The most important class of specialty plastics is polyimides. Other specialty polymers include polyetherimide, poly(amide-imide), polybismaleimides, ionic polymers, polyphosphazenes, poly(aryl ether ketones), polyarylates and related aromatic polyesters, and ultrahigh-molecular-weight polyethylene (Fig. 14.9). 

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. 

The polyester-imides constitute a class of modified polyimide. These are typified by the structure shown in Figure 4.23. Polyether-imides form yet another class of modified polyimide. These are high-performance amorphous thermoplastics based on regular repeating ether and imide linkages. The aromatic imide units provide stiffness, while the ether linkages allow for good melt-flow characteristics and processability. 

A considerable amount of research has been carried out in recent years into the design of matrix materials for the next generation of supersonic civil transports and much of it has focused on amide, imide and related structures. Among resins studied are the polystyrylpyridine (PSP) family, the polyamide-imides, polyetherimides, polyetherketones, and for very high temperatures, the polyphenylquinoxalines, the polybenzimidazoles and the aromatic polyesters [50,51]. Some generalizations emerge [52] ... 

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). 

Allied Chemical have patented the use of monoepoxides with various substituent groups such as amides or esters [131,132], imides [133] and aromatic species [134]. Taiwanese researchers used ethylene-styrene copolymers with epoxy substituents [135]. Most recently, a number of companies, including BASF [137, 141] and Mitsubishi [138-140] used epoxidised natural oils as stahilisers in aromatic polyesters. 

Hamciuc Corneliu, Vlad-Bubulac Tachita, Petreus Oana, and Lisa Gabriela. Synthesis and characterization of new aromatic polyesters and poly(ester-imide)s containing phosphorous cyclic bulky groups. Polym. Bull. 60 no. 5 (2008) 657-664. 

If monomers which form amide bonds or imide rings are involved in synthesis of aromatic polyesters, thermotropic copolyamide esters or copolyimide est are obtained. p-Aminobenzoic acid increases the strength and modulus of elasticity of a polyester plastic based on p-hydroxybenzoic acid [71]. 

Work on improving the thermal resistance and particularly the resistance to carbonization (short circuiting of layers of enameled wires under the influence of temperature) via special glycols led to diphenols [29,30]. Diphenols are not reactive under the conditions of a normal poly(ester-imide) synthesis. In synthesis the lower aliphatic diesters of diphenols were used [29-32]. The use of acid chlorides in the polyester reaction with aromatic OH-groups was also protected by patents [33-35] but it seems unlikely that this reaction was performed on the production scale. 

The reaction of trimellitic anhydride (7) with ethanolamine (9) giving the hydroxy acid (10) and with 4,4 -diaminodiphenylmethane (8) giving the diacid (11) has been published in the first poly(ester-imide) patent [l].The second one is nowadays the predominant reaction for making poly(ester-imide)s. Trimellitic anhydride is the basic dianhydride for introducing the imide structure into the polyesters. Nearly every example in patents is based on trimellitic anhydride alone or mixtures with other anhydrides, e.g., tetrahydrophthalic anhydride [59]. The imides made from aromatic anhydrides are thermally more stable than the ones resulting from aliphatic structures (Fig. 4). Both types have been protected by patents, and products made from them are on the market. 

Another possibility for obtaining imide modified thermoplastic polyesters was to use as a monomer the hydroxy acid made from trimellitic anhydride and aminoethanol. Such a poly(ester-imide) was claimed for injection molding [240]. For the same use, poly(ester-imide)s containing aminophenol/trimellitic anhydride [241],imidised polyfbutylene terephthalate) [242] and a wholly aromatic poly(ester-imide) made from trimellitic anhydride, p-aminobenzoic acid, p-acetoxybenzoic acid, diacetoxybiphenyl and terephthalic and isophthalic acids are known, which showing optical anisotropy [243]. 

Compared with aromatic thermotropic polyesters, which never form a smectic layered structure, polyimides have very strong intermolecular interactions due to the imide group. This may be attributed to the high polarity of the imide group. 

By laminating conventional polyethylene and polypropylene microporous membranes together, it is possible to obtain a separator with the desired shutdown function together with protection from rupture. Microporous membrane of liquid crystalline polyester, polyphenylene ether, aromatic polyamide, polyimide, polyamide imide resin, acrylic resin, and cross-linked polymer are now being studied as candidates for lamination with polyethylene in order to gain even greater heat resistance. 

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