the object of the present invention is a process of preparation of a graft copolymer obtained by pre - irradiation grafting of vinyl monomers onto polyolefins or fluorinated polyethylenes , in particular , of grafting acrylic or methacrylic acid onto polyethylene and / or polypropylene and subsequently loading a metal , such as a transition metal on the graft copolymer obtained . such metal - loaded graft copolymers find use , especially as catalysts , e . g . for hydrogenation reactions .