Morphology development of in situ compatibilized semicrystalline polymer blends in a co‐rotating twin‐screw extruder

This paper concerns the morphology development of in situ compatibilized semicrystalline polymer blends in a co‐rotating, intermeshing twin‐screw extruder, using polypropylene (PP) and polyamide 6 (PA‐6) blends as model systems. The morphology of in situ compatibilized blends develops much faster that of mechanical ones. The size of the dispersed phase (PA‐6) undergoes a 104 fold reduction from a few millimeters to sub‐micron during its phase transition from solid pellets to a viscoelastic fluid. The final morphology is reached as soon as the phase transition is completed, which usually requires only a small fraction of the screw length in a co‐rotating twin screw extruder. Screw profiles and processing conditions (screw speed, throughput and barrel temperature) control the PA‐6's melting location and/or rate, but do not have significant impact on the ultimate morphology and mechanical properties of in situ compatibilized blends. The finding that morphology of PP/PA‐6 reactive blend develops rapidly makes it possible to produce compatibilized PP/PA‐6 blends by the so‐called one‐step reactive extrusion. It integrates the traditionally separated free radical grafting of maleic anhydride onto PP and the compatibilization of PP/PA‐6 into a single extrusion step.