A foamed polymeric composition contains polypropylene and polyethylene components. The composition may have a gel content of about 10 to about 95 wt. %, per ASTM D 2765-01, method A, a density of about 16 kg/m.sup.3 to about 640 kg/m.sup.3 and a tensile elongation of at least about 200% at 150.degree. C. per ASTM-1708-02a, speed D. Such a composition can be produced by adding an activatable foaming agent to a base resin that contains polypropylene and polyethylene components and silane functional groups, reacting the functional groups to cause cross-linking to a gel content of about 10% to about 95%, and foaming the cross-linked base resin. Alternatively, a composition may be made by adding an activatable foaming agent to the base resin, irradiating the base resin to cross-link to the stated gel content, and foaming the cross-linked base resin. Articles may be made by molding, shaping or forming such compositions.