Ionomer present in a polyethylene resin from about 1 to 40% by weight of the resin produces superior extruded foam sheet products that approach the pore size and resiliency of foams prepared from chemical blowing agents. The results can be achieved at normal extrusion rates and on standard extrusion foaming equipment. Tear strength is improved so that collapsible foam packaging products can be produced in which the foam body is cut through except for a surface thereof that remains intact to provide a hinge or joint about which the cut foam bodies can be pivoted.