Abstract: A method is disclosed that makes a open cell cellular body of polyethylene resin material in non-crosslinked structure, which has a maximum degree of cell interconnection, is good in recyclability and excellent in heat resistance or resistance to heat distortion. The method includes the steps of adding 4,4′-oxy bis (benzene sulfonyl hydrazide) to a polyethylene resin material to form a foamable composition and shaping the foamable composition of polyethylene resin material, heating the shaped foamable composition of polyethylene resin material to be foamed under an atmospheric pressure to form a cellular body thereof with cells therein, and mechanically deforming the cellular body of polyethylene resin material to cause the cells therein to be interconnected, thereby producing the open cell cellular body desired. The produced continuous cellular body is rendered heat resistant by irradiating the same or the formed cellular body with a beam of electrons.

Abstract: An open-cell cross-linked polyolefin foam possessing extremely high non-flammability is produced by dispersing a thermally expansible graphite in an adhesive agent and applying the resultant adhesive agent mixture to at least part of the surface of a flame-retardant open-cell cross-linked polyolefin foam. As the flame-retardant open-cell cross-linked polyolefin foam, an open-cell cross-linked polyolefin foam which possesses a polymer of a phosphorus type flame-retarding agent in the interior and the surface of the open-cell foam or an open-cell cross-linked polyolefin foam which contains a halogen type flame-retarding agent in the cell membranes thereof and possesses a polymer of a phosphorus type flame-retarding agent in the interior and the surface of the open-cell foam is preferably used.