Ethylene-vinyl acetate rubber (EVM) vulcanizates with excellent mechanical properties were obtained with magnesium hydroxides (MH) and methacrylic acid (MAA). MAA significantly improved the mechanical properties of the MH-filled EVM vulcanizates. The tensile strength, Shore A hardness, and tensile set modulus of the EVM vulcanizates significantly increased with increasing MAA content. The tensile strength of the MH-filled EVM vulcanizates increased from 12.3 to 18.5 MPa after the addition of 2.5 phr MAA when the MH content was fixed at 60 phr. The gross crosslink density and ionic crosslink density increased with increasing MAA content. The glass-transition temperature and tan delta slightly decreased with increasing MAA content. Morphological study showed that MAA obviously improved the dispersion of the MH particles in the EVM matrix. The thermal stability of the EVM vulcanizates was obviously enhanced after the addition of MAA. Fourier transform infrared analysis indicated that MAA reacted with MH to form magnesium methacrylates, and there was a polymerization of MAA during the curing process in the existence of peroxide. An ionic crosslink bond was thought to be formed on the surface of the MH aggregates; this resulted in a possible structure where MH aggregates were considered as crosslink points. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 279-285, 2011