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 i t play central roles in the processing of polymer blends. We studied the im pact of speed, melt throughput, continuous-phase viscosity, screw configura tion, and disperse-phase content on the melting behavior and morphology dev elopment in the melting zone of a twin-screw extruder. The polymer blend us ed incorporated polyamide-6 (PA6) as its disperse phase and a high-viscosit y or low-viscosity polypropylene as the matrix phase. The melting behavior of the polymer blend was investigated with press plates. A qualitative asse ssment was made of the processes, on basis of the optical impression gained from the transilluminated press plates. One key result was that the PA6 gr anules melted very rapidly in the polypropylene melt. We took samples over the length of the melting section to permit a quantitative assessment of th e 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. (C) 2001 John Wiley & Sons, Inc.