Reactive blending of polymers by interfacial free‐radical grafting

In blends of immiscible polymers, amphiphilic species are needed for both morphological stabilization and improvement of the mechanical properties throughout successive processing steps. In order to obtain the required concentration of amphiphilic copolymer at the interface, it seemed of interest to test the possibility of creating these species by in situ reactivity at the interface, for instance by condensation reactions occurring between functionalized polymers. There is another possibility based on the fact that most of the polymers are hydrocarbon compounds, so they are subjected to free‐radical reactivity by hydrogen abstraction on the different hydrocarbon sites. The created free‐radical polymeric species may react together leading to the well known reactions of crosslinking, grafting and/or chain degradation. Therefore, this work deals with reciprocal free‐radical reactivity of two kinds of semi‐crystalline polymers, namely one polyolefin (LDPE, HDPE, PP or EPR) associated with a polyamide (PA‐11 or PA‐6). The reaction has to occur mainly at the interface, where the resulting grafted copolymers have to be anchored for final stabilization of the biphasic system. The level of interfacial grafting and the resulting properties of the reacted blends were characterized carefully, confirming the efficiency of the interpolymeric grafting.