Blowing agents in polymer foam processing systems

A method comprising:

• providing a hopper of a polymer foam processing system;
• supplying polymeric material to the hopper;
• supplying chemical blowing agent to the hopper;
• supplying physical blowing agent to the hopper;
• supplying the polymeric material, chemical blowing agent and physical blowing agent to an inlet of an extruder including a screw configured to rotate in a barrel;
• conveying a mixture of polymeric material, chemical blowing agent and physical blowing agent in a downstream direction in the extruder;
• accumulating a shot of the mixture of polymeric material and blowing agent;
• and
• injecting the shot into a mold to form a molded polymeric foam article.