Abstract: Polycarbonate copolymers from bisphenol-A containing terephthalate moieties constituting 5 or 10 mol percent of the polymer, whereby after long exposure to working temperature the polymer retains Izod impact resistance of at least 9 ft. -lbs. per inch of notch.

Abstract: Copolymers consisting of bisphenol-A ("BPA"), terephthalate ("TP"), and carbonate moieties in mol ratio from 2:0.8:1.2 to 2:1.3:0.7, which are melt processable in the sense of (a) showing no more than 10% change in viscosity number upon compression molding for 10 minutes at 320.degree. C. to form a plaque, (b) developing, in 2% (gm./ml.) DCM solution, a "yellowness index" of no more than 10 as observed by ASTM Test No. D-1925, using a 2 cm. path length; which copolymers approximate in properties the alternating copolymer consisting of the above moieties, as indicated by their having viscosity numbers ("I.V.") in the range between 0.6 and 1.5 dl./gm. and T.sub.G of 170.degree. to 194.degree. C., with T.sub.G vs. I.V. relationship conforming to the formula, T.sub.G =192-(11.5/I.V.)+9 and with difference of (T.sub.G -HDT) of not over 15.degree. C.; having Izod impact resistance (ft.-lb. per inch of notch) at 25.degree. C. of at least 5; and being essentially free of pyridine and of anhydride linkages.