Extrusion foaming of neat PS and recycled PS with chemical materials as foaming agents was studied.Foaming behaviors of recycled PS using modified exothermic AC,modified endothermic NaHCO3,and exothermic-endothermic composite blowing agents were compared regarding the density,cellular structure,and cellular uniformity of recycled PS foam.When the blowing agent content was 1 %,the density of the foam using AC and exothermic-endothermic composite blowing agents was 0.47 g/cm3 and 0.39 g/cm3,respectively.