Itaconic acid (IA) was grafted onto polypropylene/low-density polyethylene (PP/LDPE) blends. The ratio of polymeric components was varied from 100: 0 to 0: 100. The effect of the variation in the ratios of the components on grafting efficiency and concomitant side processes was studied. Grafting of IA (1 wt %) was initiated by 2,5-dimethyl-2,5di(tert-butyl peroxy)-hexane (0.3 wt %) and was carried out in an extruder reactor equipped with a dynamic mixer. An increase in the PP content of the blend led to a lower yield of the grafted product. With low concentrations of LDPE in the blend (up to 25 wt %), grafting efficiency was observed to increase, and this increase was greater in comparison with the additive rule. Between 25 and 99 wt % of LDPE in the blend, grafting efficiency rose monotonically with LDPE concentration. At or below an LDPE content of 25 wt %, the melt flow index (MFI) of [PP/LDPE]-g-IA would increase unlike with PP-g-IA systems. But a small quantity of PP (below 25 wt %) in the [PP/LDPE]-g-IA blends would result in a decreased MFI unlike with LDPE-g-IA. The dependence of swell index and melt strength on the ratio of polymeric components in [PP/LDPE]-g-IA blends also was investigated. (c) 2006 Wiley Periodicals, Inc.