The compatibilization of HDPE/LDPE/LLDPE/PET blend during reactive extrusion, using compatibilizing agents, such as modified high, low, and lineal low density polyethylenes with maleic anhydride, was carried out. The agents were prepared in our laboratory by using a UV preirradiation process, containing different grafting and crosslinking degrees. The materials were compared with same maleic anhydride modified polyethylenes prepared by the traditional peroxide method in our laboratory and with a commercial maleic anhydride modified lineal low density polyethylene. The mechanical and thermal properties, as well as their morphology, were evaluated in the compatibilized blends and changes in crystallization phases recorded. The elongation at break and impact strengths increased with compatibilization. level and morphology was markedly more homogenous. (c) 2007 Wiley Periodicals, Inc.