Polyester-imides

The successful introduction of the polyimides stimulated attempts to produce somewhat more tractable materials without too serious a loss of heat resistance. This led to the availability of a polyamide-imides, polyester-imides and the polybismaleinimides, and in 1982 the polyether-imides. 

The polyester-imides form yet another class of modified polyimide. These are typified by the structure shown in Figure 18.43. 

LC polyesters belong to the class of thermotropic main-chain LCPs, which also comprises polymers such as polycarbonates, polyethers, polyphenylenes, polyester-imides, polymers containing azo- or azo V-oxide linking groups, some cellulose derivatives, and polypeptides such as po 1 y (y - be n zy 1 -1. - g 1 u tamate). Both from the academic and industrial points of view, polyesters are by far the most important representatives of this class of polymers. 

Polyamide imides and polyester imides are more flexible and more readily processed than polyimides. 

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. 

Effect of thermostabilizers on the polymer properties was studied by different physicochemical methods. For example, in the work [260] method of DSS (differential spectroscopy) was used to define the effect of polyester-imide on thermo-physical properties of PETP. By this method it was found out that polyester-imide reduces PETP ability to crystallization. Methods of thermogravimetric analysis (TGA) and infrared spectroscopy in the nitrogen atmosphere were used in the work [261] to define thermal stability of the mixture of PETP and polyamide with the additive - modifier - polyethylene. It has been found that introduction of the additive decreases activation energy which positively tells on the ability of PETP to thermal destruction. 

Within the extensive literature on this subject, there are many examples of the synthesis of thermotropic polyesters, polyesteramides, polycarbonates, polyethers, polyurethanes and polyester-imides. Until recently, the main omissions had been thermotropic polyamides and polyimides however, many examples of polyamides that show lyotropic behaviour have been known for a long time. 

Polyester Imide Enamels. The chemistry of the polyester Imide enamels differs from that of the polyesters in that methylene dianiline is one of the basic building blocks. Reaction with anhydrides such as trimellitic anhydride provides for the imide content, and the remaining acid group of the trimellitic anhydride is available to form ester linkages. 

Wire enameled with polyester imides can be used for applications in which it is occasionally exposed to temperatures in the 155-180 C range. One of the most demanding environments is in hermetic motors used in refrigerators where the insulating enamel film is exposed at elevated temperatures to oil and refrigerants under pressure. 

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. 

Isomid . [Schenectady] Polyester-imides wire enamels. 

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. 

Diamino-1,2,4-triazole is a component in polyester imide coatings with increased hardness that is used for thermosetting insulating varnishes for coating of electric wires. Acid components are terephthaUc acid esters and trimelUtic acid anhydride. 

The same techniques are applied to preparations of polyester-imides. A diester can first be formed from trimellitic anhydride ... 

The product is then condensed with a diamine to form a polyester-imide ... 

Most polyamide-imides are not as heat resistant as are the polyimides discussed in the next section. They are, however, easier to process. The polyester-imides might be considered as upgraded polyesters, though properties vary, depending upon chemical structure. ... 

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

Uses Additive to plastics, esp. to impart thermal stability crosslinking agent for polyester-imide and PU plasticizer for melamine... 

The polyimides are mechanically stable in air up to about 350 C and do not significantly distort at even higher application temperatures. But they are difficult to produce and to work. Polyimide amides and polyester imides do not have these disadvantages, but because of this, also have less advantageous thermal stabilities. They are produced by directly converting diamines with trimellitic anhydride or by reaction of diamines with a precursor from trimellitic anhydride and phenolic esters, e.g.. 

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

Polyester imide n. A polymer containing both ester and imide groups in the polymer chain. 

Several classes of P- and N-containing polymers have been reported in literature. These include polybenzimidazoles, polyester-imides, polyamide-imide, polyanhydride-imides, polyurethanes, polyamides, and polymaleimide-amines. Heretofore, phosphorus-containing bisimide resins have received little attention. Bisimide monomers, which cure by addition-type polymerization without the elimination of volatile products, are suitable as matrix resins for fabrication of graphite-fabric reinforced composite materials. 

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