The invention relates to a thermoplastic formulation having a thermoplastic matrix and 1-40 percent by weight of a high molecular weight acrylic processing aid, with a weight average molecular weight of greater than 100,000 g/mol. The formulation has a high melt strength, yet is processable under typical melt processing conditions. The formulation is useful for melt-processed products, including extruded products such as extruded sheet, foam, co-extruded profiles, blown films, and other objects typically formed by a heat processing operation.