The improvement of the properties of commingled plastics was carried out with a prototype blend of Mexican municipal plastic waste with and without poly(vinyl chloride) (PVC). Compatibilizing agents such as high-density, low-density, and linear low-density polyethylenes modified with maleic anhydride were used. The agents were prepared in the laboratory with peroxide, and their usefulness was compared with that of a commercially modified linear low-density polyethylene. The blends with PVC were preirradiated with ultraviolet radiation for 12, 24, or 48 h to create oxidized groups to help in situ compatibilization during the blending step of the reactive extrusion process. Compatibilized materials showed a markedly more homogeneous morphology with improved mechanical properties: the elongation at break and impact strength increased with the compatibilization level. The presence of PVC in commingled plastics significantly reduced the beneficial effect of the maleic anhydride modified polyethylene as a compatibilizer. (C) 2008 Wiley Periodicals, Inc.