Aromatic polyesters solvent resistance

Polyesters are, in general, organic solvent resistant. They show excellent room temperature resistance to organic solvents, such as hydrocarbons, alcohols, and chlorinated hydrocarbons. At slightly elevated temperatures of approximately 60 °C, alcohols and aromatic solvents can damage the polymer. Strong acids and bases can cause chemical damage to polyesters, as can ketones and phenols. 

The lowest cost process for preparing all-arcmatic liquid crystalline polyesters involves the reaction of aromatic carboxylic acids with acetates of aromatic hydroxy ocnpounds a recent history (2) describes the development of these ICP s. Because aoetic acid is evolved in the process and reaction temperatures are above 300°C, expensive corrosion-resistant reactors must be installed for ccranercial production. In cur latest paper (2) of this ICP series, we described a number of aliphatic-aromatic ICP s which can be produced in conventional polyester reactors and injection molded to give plastics with very high mechanical properties, heat-deflection temperatures (HDT s), and solvent resistance. These ICP s (la) were prepared by the reaction of the dimethyl ester of... 

Aromatic polyesters have hydrophobic phenyl groups that allow them to take up only very small amounts of aqueous solvents, so that hydrolysis is oidy observed at raised temperatures and the materials generally show a good level of resistance to cold water. 

Highly durable, chemically inert, thermo-stable aromatic polyesters can be produced by interaction of polymers containing links of -oxyben-zoic acid, aromatic dioxy-compounds, for example of hydroquinone and aromatic dicarboxylic acids [40]. Thermo and chemically resistant polyesters of improved mechanical strength can be obtained by the reaction of n-oxybenzoic acid, aromatic dicarboxylic acids, aromatic dioxy-compounds and diaryl carbonates held in solid phase or in high-boiling solvents [41] at temperature 180 °C and lowered pressure, possibly in the presence of catalysts [42], Some characteristics of aromatic polyesters based on n-oxybenzoic acid are gathered in Table 7.1 [20],... 

Phenothiophosphine ring-containing polyamides and polyesters were also prepared by the polycondensation of 2,8-bischloroformyl-lO-phenylphenothiophos-phine 5,5, 10-trioxide with aromatic diamines such as 4,4 -diaminodiphenyl ether and 4,4 -diaminodiphenyl-methane, and bisphenols such as 4,4 -dihydroxybiphe-nyl and 4,4 -dihydroxydiphenylmethane, respectively [159]. These polymers are soluble in polar aprotic solvents and also exhibit good heat and fire resistance. Phosphorus containing high performance polymers are shown in Table 6. 

The sensitivity to hydrolysis is a key issue in many applications. The ester bond in 4GT-PTMO copolymers is sensitive to hydrolysis however, it is fairly protected since most of the ester is contained in a crystalline structure. The addition of a small amount (1-2%) of a hindered aromatic polycarbodiimide substantially increases the lifetime of this material in the presence of hot water or steam (Brown et al., 1974). Polyurethanes are susceptible to hydrolytic attack, especially those with polyester soft segments. However, polyester soft segment polyurethanes are generally more resistant to oils, organic solvents, and thermal degradation. lonomers will swell when exposed to water in fact, a commercial hydrated perfluorosulfonic ionomer (Nation) is used as a membrane separator in chlor-alkali cells. Styrene-diene copolymers and polyolefin TPEs are insensitive to water. 

Further incorporation of metal ions and aromatic structure in the main chain of these polyester enhances the thermal stability as well as resistance towards solvents. Owing to these properties, these metal-containing polyesters may be used for hard surface coatings where thermal resistance is required. 

The standard does not relate to the petroleum products containing oxygenates (for example, MTBE - Methyl tert-butyl ether) or aromatic solvents (toluene, benzene and xylene), added to increase the octane number. It was recommended to re-examine the resistance of the polyester coatings in the fuels containing oxygenates [8]. 

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