polyesters of the general formula [—OAOOCA′CO—]n, produced by polycondensation of diacid chloride derivatives of dicarboxylic acids with dihydric phenols. In the above formula A is a phenol radical, most often 4,4’-dihydroxydiphenyl-2,2-propane, phenolphthalein, or 9,9-bis- (4-hydroxyphenyl)fluorene, and A’ is the dicarboxylic acid radical.
Polyarylates of aromatic dicarboxylic acids (mainly terephthalic and isophthalic acids) are of practical importance. These polyarylates, whose molecular weight is 100,000–160,000, have high softening points (200–360°C), good dielectric and mechanical properties, and high heat resistance (they begin to decompose only at about 300°C). They can withstand prolonged operation at 200°-280°c Polyarylates are also resistant to the action of fats, liquid fuels, and a number of organic solvents and dilute mineral acids, but they are not resistant to the action of alkalies, ammonia, and concentrated acids (for example, sulfuric and nitric acids). The highly crystalline polyarylate based on p- hydroxybenzoic acid, which is known by the trade name Ekonol (USA), is superior to polyimides in heat resistance (380°-400°C) and is similar to polyfluoroethylene resins in chemical resistance.
Polyarylates are processed by injection molding, extrusion, and compression molding; soluble polyarylates are processed from solutions in organic solvents. Polyarylates are used to make structural parts, films, fiber materials for the fine filtration of gases, and synthetic paper, mainly for electrical and radio engineering items.
The brands of polyarylates produced in the USSR are DV-101, F-l, and F-2.
A specific group of polyarlyates is the polycarbonates.
REFERENCESSee References under .
P. M. VALETSKII