Polyethylenes Modified by Irradiation and Organic Peroxide Treatment: Rheological Study

− A series of polyethylenes was obtained by modification of two commercial high-density polyethylenes. The organic peroxide concentrations and irradiation dosis used are below the critical ones that produce molecular networks. The molecular weights of the polymers increase, and the molecular weight distribution gets wider, as the concentration/dose increases. These results are a consequence of the large molecular weight molecules generated during the chain-linking modification processes. By the time traces of gel begin to appear in the samples, the peroxide modified materials display larger molecular weights and smaller vinyl concentrations than the irradiated ones. The rheological behavior of these materials is analyzed as a function of the molecular structure of the polymers and the concentration/dose used in the modification processes. All the modified polymers show a complex thermo-rheological behavior associated to the presence of longbranched macromolecules. The peroxide treatment generates the polymers with the largest rate of change of flow activation energy. Keywords− Polyethylene, Rheology, Modification, Irradiation , Peroxide.