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An ethylene polymer composition is provided, the composition being a blend of a first ethylene polymer and a second ethylene polymer, the second ethylene polymer characterized by molecules having long chain Y-branches. The blend can be prepared by an extrusion process in which a portion of the polye

An ethylene polymer composition is provided, the composition being a blend of a first ethylene polymer and a second ethylene polymer, the second ethylene polymer characterized by molecules having long chain Y-branches. The blend can be prepared by an extrusion process in which a portion of the polyethylene fed to the process is irradiated and the irradiated and non-irradiated polymers are blended by melt extrusion. The blends exhibit high flow activation energies and good blow-molding properties.

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A composition comprising a blend of (a) a first polymer selected from normally solid crystalline ethylene homopolymers and copolymers of ethylene containing up to about 20 mole percent of at least one comonomer selected from a3 to about 20 carbon atoms, said polymer having repeating units of the str

A composition comprising a blend of (a) a first polymer selected from normally solid crystalline ethylene homopolymers and copolymers of ethylene containing up to about 20 mole percent of at least one comonomer selected from a3 to about 20 carbon atoms, said polymer having repeating units of the structure －CH2－and a density greater than about 0.95 g/cm3, and (b) a second polymer selected from the group consisting of (1) non-gelled, normally solid crystalline ethylene homopolymers having repeating units of the structure －CH2－and at least about two long chain Y-branches per 10,000 carbon atoms and fewer than about 10 short chain branches per 10,000 carbon atoms; (2) non-gelled, normally solid crystalline ethylene homopolymers and copolymers of ethylene containing up to about 20 mole percent of at least one comonomer selected from a3 to about 20 carbon atoms, having repeating units of the structure －CH2－and a g value of less than about 0.9 and an intrinsic viscosity of less than about 3.0; (3) non-gelled, normally solid crystalline ethylene homopolymers and copolymers of ethylene containing up to about 20 mole percent of at least one comonomer selected from a3 to about 20 carbon atoms, having repeating units of the structure －CH2－and comprising molecules exhibiting a numerical excess of long chain Y-branching over short chain branching; and (4) non-gelled, normally solid crystalline ethylene homopolymers and copolymers of ethylene containing up to about 20 mole percent of at least one comonomer selected from a3 to about 20 carbon atoms, having repeating units of the structure －CH2－and comprising molecules having at least 2 long chain Y-branches per 10,000 carbon atoms and flow activation energy E* greater than 20 kcal/mole. In a polymer extrusion process in which a polymer selected from ethylene homopolymers and copolymers having a density greater than about 0.95 g/cm3 is extruded in the melt and the extruded polymer is cooled to produce a solid polymer, a process comprising prior to or during extrusion of the polymer, exposing a portion of the polymer in the melt to radiation under non-gelling, non-oxidizing conditions, wherein the extruded product comprises a mixture of high density ethylene polymer and Y-branched ethylene polymer.