To reduce the ZnO levels in rubber compounds, mixed metal oxide nanoparticles of zinc and magnesium (Zn1-xMgxO) have been synthesized and used as activator. The aim is to obtain better curing properties due to its nanosize and to take advantage of the behavior of both ZnO and MgO in sulfur vulcanization. The model compound vulcanization approach with squalene as a model molecule for NR and CBS as accelerator has been used to study the role of the mixed metal oxide along the reaction. The results found show that with Zn1-xMgxO nanoparticles the reaction of CBS becomes faster, higher amounts of MBT are formed at shorter reaction times, and the consumption of sulfur occurs faster in comparison with standard ZnO. Furthermore and more important, an increased crosslink degree calculated as the total amount of crosslinked squalene is obtained. All these findings indicate that Zn1-xMgxO is a promising candidate to reduce the ZnO levels in rubber compounds. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 2048-2057, 2011