Abstract: Thermoplastic compositions comprising, in intimate admixture, polyethylene terephthalate, a rubber-free copolymer of or a rubber-modified graft copolymer of a vinyl aromatic compound and an .alpha.,.beta.-unsaturated cyclic anhydride, a fibrous modifier, and a nucleating agent are disclosed. These compositions display desirable properties, particularly elevated heat deflection temperatures and good surface appearance.Also disclosed is a process for producing articles by injection molding the compositions at a hold pressure of about 5,000 to about 10,000 psi.

Abstract: A process is provided for increasing the rate of crystallization of polyester compounds, such as poly (alkylene arylates), more particularly poly(alkylene terephthalates), or blends or mixtures thereof, as for example, poly(ethylene terephthalate), poly(butylene terephthalate) or mixtures of blends thereof, by incorporating therein a small amount of a polyethylene ionomer, or an alkali metal salt of benzoic acid, such as sodium benzoate. The faster crystallization rates improve injection molding performance of the polyesters and blends thereof, such as reduced post-mold shrinkage, faster mold cycle times and lower mold temperature. Also, the resultant products show increases in physical properties such as flex modulus, flex strength, deflection temperature under load (DTUL), tensile strength and solvent resistance.