Glycidyl methacrylate (GMA) was grafted onto natural rubber (NR) using emulsion polymerization method. The structures of copolymers were characterized by 1 H nuclear magnetic resonance ((1)H-NMR), solid state (13)C-NMR spectroscopy, and Fourier transform infrared spectrometer (FTIR). The %grafting obtained from the gravimetric method and the absorbance ratio were compared. Effects of reaction temperature, GMA content, and reaction time on %grafting, grafting efficiency, and %conversion of GMA monomer were determined. Effect of %grafting on mechanical properties of the graft copolymer was studied. Experimental result showed that the appropriate reaction time was 8 h at a reaction temperature of 30 degrees C. Moreover, tensile strength and modulus of the graft copolymer increased with increasing %grafting. However, elongation at break of the graft copolymer decreased with increasing %grafting. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 3152-3159, 2011