A new additive for plastics (for example, polyethylene) is prepared by reacting a fatty acid ester of glycerol (such as glycerol monostearate) with a source of a reactive divalent metal selected from zinc, calcium, and magnesium. In an embodiment, Zinc oxide is the reactive divalent metal and the reaction is conducted in the presence of an acid such as zinc acetate. In one embodiment, a molar excess of zinc oxide (compared to the fatty acid ester) is used. The additive is suitable for use in the preparation of injection molded parts, rotomolded parts, and films.