Metallocenic polypropylene and copolymers with 3.7, and 9.2 mol% of hexene and 3.0 mol% of octadecene comonomer content were synthesized without the presence of additives and irradiated with Co-60 gamma radiation under vacuum at room temperature. Size Exclusion Cromatography and gel extraction data showed that scission reactions predominate over crosslinking in the homopolymer and that there is a dose from where crosslinking started to increase considerably, in the irradiated copolymers. Rheology also showed evidence of chain-enlargements on the copolymers by means of an increase in the viscoelastic properties of the irradiated material. (C) 2012 Elsevier Ltd. All rights reserved.