of copolyester of the invention other essential and optional ingredients of compositions of the invention are preferably added by blending with previously polymerized copolyester all such ingredients or portions thereof may however be present during polymerization of the copolyester so long as the polymerization reaction is not interfered with blending with copolyester may be carried out in any suitable manner such as in conventional mixing equipment with extrusion compounding being preferred elastomers of the invention exhibit superior retention of mechanical properties especially tensile strength and improved brittleness characteristics at elevated temperatures such elastomers are especially suited for use in molding various articles such as tires hoses drive belts gears etc such elastomers can be made in grades of low melt flow rate this permits faster molding cycle times and allows the manufacture of blow molding grades of elastomers of the invention both cyanoguanidine cng and guanidine stabilizers of formula iii are quite effective for stabilizing elastomer of the type used in the invention cng will however plate out onto extrusion processing equipment this results in extruded parts which have dull surfaces guanidine stabilizers of formula iii tend to bloom resulting in dull greasy appearing surfaces on finished products use of pvp along with cng or stabilizer of formula iii in compositions of the invention substantially eliminates such plate out or blooming and resulting dull surfaces on extruded products it has further been found that pvp alone has a significant stabilizing influence on elastomers of this type containing pvp or pvp plus guanidine is further improved by the use of diphenylamine and phosphorous stabilizer as described herein the following examples are intended to illustrate the invention without limiting the.