Abstract: In one aspect, a method for forming a foamable polypropylene extrusion mixture includes providing a polypropylene resin and blending a nucleating agent, a polymer stabilizer, and a physical blowing agent with the polypropylene resin. In another aspect, a method for forming a foamable polypropylene extrusion mixture includes providing a polypropylene resin and blending a nucleating agent, a polymer stabilizer, a physical blowing agent, and a chemical foaming agent with the polypropylene resin. In further aspects, a foamable polypropylene extrusion mixture and foam articles are provided. The foamable polypropylene extrusion mixtures are extrudable to form a polypropylene foam sheet or web which is thermoformable to produce a polypropylene foam packaging tray having superior rigidity and puncture resistance.