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

Abstract

ABSTRACT: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 dispersephase 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.

Melting of polymer blends in single-screw extrusion - an experimental study

“…The horizontal lines correspond to the values expected for each polymer after complete melting, taking into account their relative density and relative percentage. In the feeding zone (screw turns 1-10), the melting rate of the blends is essentially determined by the PP melting rate, whereas in the compression zone (screw turns [11][12][13][14][15][16][17][18][19][20] the role of PA6 seems predominant. Moreover, in the feed zone (screw turns 1-10), the higher the PP content in the blend, the higher the melting rate of this polymer.…”

“…The above experimental observations and models typically consider processing of homopolymers, or of very simple polymer systems. The study of melting of (immiscible or reactive) polymer blends is much less common and seems to be limited to twin screw extrusion [16][17][18]. It is well known that the morphologies formed upon melting will influence the final morphologies obtained which, in turn, will determine the mechanical properties [19][20][21].…”

Morphological evolution of polypropylene/polystyrene blends in a twin‐screw extruder

“…As the industrial importance of immiscible polymer blends is increasing, it is of crucial importance to understand in detail the fundamental parameters controlling the blend phase morphology during the mixing process because most properties of blends of immiscible polymers depend on the fineness of the phase morphology 1–10. The effects of the material characteristics (interfacial tension, melt viscosity, melt elasticity, and molecular weight), processing conditions (time of mixing, temperature of mixing, rotation speed, and mixer type), and blend composition on the final blend phase morphology have been studied extensively 11–16…”

Submicron structured polymethyl methacrylate/acrylonitrile–butadiene rubber blends obtained via gamma radiation induced “in situ” polymerization

“…Physical blending, the most common technique, involves mixing two immiscible polymers using processing equipment, such as extruders, injection moulders, rolling mills, etc. [11][12][13][14][15] The final morphology is determined by both the processing conditions and some intrinsic properties of the two polymers involved (viscosity, mutual solubility, interfacial tension, etc.). Besides adding another component in the blend as a compatibilizer in order to reduce the size of the dispersed phase, [16][17][18] not much can be done to affect the final morphology.…”