itself and thus is a good indicator as to the usefulness of the thermoplastic product for different types of end uses the lower the extraction level the more useful such thermoplastic is for food contact for example the data demonstrate that the inventive product in example 1 shows extraction levels comparable to thermoplastic samples containing no nucleator at all and thus indicates that such thermoplastic may be useful for various end uses one method of evaluating the nucleating efficiency of a nucleating agent in a given resin is to calculate the density of nucleating sites per unit volume of polymer as well as comparing such density measurements at differing isothermal crystallization temperatures the greater the density of nucleating sites the better the nucleating agent the higher the ratio of densities between different isotherms the more versatile the nucleating agent for these purposes the effective nucleation densities for the inventive and comparative nucleating agents were calculated by combining isothermal crystallization kinetic data measured using differential scanning calorimetry and spherulitic growth rate data measured with optical microscopy a perkin elmer dsc 7 was calibrated with an indium metal standard at a heating rate of 20 c min polymer samples with a thickness of 250 u2212 50 microns and a weight of 5 0 u2212 0 5 mg were encased in aluminum pans the pans were then heated from 60 u00b0 c to 220 u00b0 c at 20 u00b0 c min held 2.