Maleic anhydride was melt-grafted onto poly(ethylene-co-methyl acrylate) using a free-radical initiator, Lupersol 231, in an internal batch mixer at 140 degrees C. The grafting was conducted in the presence of a second monomer (synergistic co-monomer): vinyl 4-t-butylbenzoate, styrene or 1-dodecene. The effects of varying monomer:co-monomer ratio and the initiator concentration on the weight percent of anhydride grafted were examined; melt flow indices were determined as an indicator of crosslinking. It was observed that styrene and vinyl 4-tertbutylbenzoate could be used to significantly increase the amount of anhydride grafted. (C) 2000 Elsevier Science Ltd. All rights reserved.