Low-d. polyethylene was compounded with ZnO or Zn stearate, chalk, azodicarbonamid porofor and antioxidants, formed as plates, crosslinked under electron irradn. (60-110 kGy) at room temp., foamed by heating at 210 degrees C to 2-3 mm thick foam plates and studied for apparent d. and gel no. The addn. of Zn compds. resulted in shortening the crosslinking and foaming times and in increasing the crosslinking d.