There is provided a polyethylene film and a laminate which can be used to produce a package having high heat resistance, strength and recycling suitability in place of a lamination film conventionally used in a package. The polyethylene film of the present invention is irradiated with an electron beam on its only one side, and comprises polyethylene and a crosslinking agent, in which the crosslink density of the polyethylene is different between the side irradiated with an electron beam and the other side not irradiated with an electron beam.

A process for treating elastomeric materials with supercritical CO.sub.2 such that they can be used or reused as intended prior to exposure to supercritical CO.sub.2. The process includes the following steps: (a) loading the elastomeric materials into a vessel and closing the vessel; (b) introducing CO.sub.2 into the vessel and creating a supercritical CO.sub.2 environment within the vessel; (c) subjecting the elastomeric materials contained within the vessel to the supercritical CO.sub.2 environment for a predetermined period of time; (d) after the predetermined period of time introducing an inert gas under controlled pressure into the vessel to force the supercritical CO.sub.2 out of the vessel; (e) continuing introducing inert gas until the supercritical CO.sub.2 has been exhausted from the vessel; maintaining the inert gas within the vessel at least 1,500 psi to create an inert gas environment within the vessel to subject the elastomeric materials contained within the vessel to the inert gas environment for a time period sufficient to penetrate the elastomeric materials; (f) depressurizing the vessel to 0 psi by exhausting the inert gas from the vessel; and optionally including the step of filling the vessel with an inert gas under pressure prior to step (b) introducing CO.sub.2 into the vessel and creating a supercritical CO.sub.2 environment within the vessel.

A process for treating elastomeric materials with supercritical CO.sub.2 such that they can be used or reused as intended prior to exposure to supercritical CO.sub.2. The process includes the following steps: (a) loading the elastomeric materials into a vessel and closing the vessel; (b) introducing CO.sub.2 into the vessel and creating a supercritical CO.sub.2 environment within the vessel; (c) subjecting the elastomeric materials contained within the vessel to the supercritical CO.sub.2 environment for a predetermined period of time; (d) after the predetermined period of time introducing an inert gas under controlled pressure into the vessel to force the supercritical CO.sub.2 out of the vessel; (e) continuing introducing inert gas until the supercritical CO.sub.2 has been exhausted from the vessel; maintaining the inert gas within the vessel at least 1,500 psi to create an inert gas environment within the vessel to subject the elastomeric materials contained within the vessel to the inert gas environment for a time period sufficient to penetrate the elastomeric materials; (f) depressurizing the vessel to 0 psi by exhausting the inert gas from the vessel; and optionally including the step of filling the vessel with an inert gas under pressure prior to step (b) introducing CO.sub.2 into the vessel and creating a supercritical CO.sub.2 environment within the vessel.