Investigation of the melting behavior and morphology development of polymer blends in the melting zone of twin-screw extruders

The melting behavior and the morphology development that runs parallel to it play central roles in the processing of polymer blends. We studied the impact of speed, melt throughput, continuous-phase viscosity, screw configuration, and disperse-phase content on the melting behavior and morphology development in the melting zone of a twin-screw extruder. The polymer blend used incorporated polyamide-6 (PA6) as its disperse phase and a high-viscosity or low-viscosity polypropylene as the matrix phase. The melting behavior of the polymer blend was investigated with press plates. A qualitative assessment was made of the processes, on basis of the optical impression gained from the transilluminated press plates. One key result was that the PA6 granules melted very rapidly in the polypropylene melt. We took samples over the length of the melting section to permit a quantitative assessment of the morphology. The results show a finely dispersed morphology already at the start of the melting section. This did not undergo any essential change as the blend passed through the extruder, and only a limited correlation was evident with the process parameters. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1986–2002, 2001