Polyester compositions are disclosed that include polyester polymers or copolymers having incorporated therein metallic nickel particles that improve the reheat properties of the compositions. Processes for making such compositions are also disclosed. The nickel particles may be incorporated in the polyester by melt compounding, or may be added at any stage of the polymerization, such as during the melt-phase of the polymerization. A range of particle sizes may be used, as well as a range of particle size distributions. The polyester compositions are suitable for use in packaging made from processes in which a reheat step is desirable.