PP/LDPE blends produced by reactive processing. I. Grafting efficiency and rheological and high‐elastic properties of [PP/LDPE]‐ g ‐IA melts

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‐2,5‐di( 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. ©2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5095–5104, 2006