Grafting of undecylenic acid on ethylene-octene copolymer (POE) in the molten state has been investigated. Haake Rheocord RC90 mixer has been used as a blender of reagents and chemical reactor. Dicumyl peroxide; 2,5-dimethyl-2,5-(tert-butylperoxy)hexane (DMDBH); tert-butyl hydroperoxide (TBHP) were used as peroxide initiators of grafting. The influence of initiator concentration, monomer concentration and reaction temperature on grafting was discussed. (C) 2004 Elsevier B.V. All rights reserved.