Diacetals of sorbitols and xylitols are employed in polyolefins as nucleating agents. Diacetals of sorbitols and xylitol nucleating agents may be provided in granular or powder form from hoppers or mixing equipment into polyolefins during the formation of polymeric compositions and polymeric articles. Flow of diacetals of sorbitols and xylitols is improved by the use of certain silicas, in certain defined weight percentages. Submicron size range silica compounds may provide excellent flow enhancement properties when blended and used with diacetals of sorbitols and xylitols powder compounds. A hydrophobic silica mixed with diacetals of sorbitols and xylitols compounds also may provide enhanced flow properties for such mixture, as compared to mixtures using hydrophilic silica. Loading ranges of silica may be important in improving the flow of diacetals of sorbitols and xylitols compounds.