Journal of macromolecular science-physics vol:B43 issue:5 pages:1025-1043
The evolution of phase morphology in uncompatibilized and reactively compatibilized nylon-6/ethylene propylene rubber (EPR) blends has been investigated by scanning electron microscopy with special reference to the effect of mixer type and size. Three types of mixing instruments were used for the melt preparation of the blends. These include the Haake Rheocord mixer, the DSM twin-screw mini extruder, and the industrial Werner Pfleiderer twin-screw extruder (ZSK-25). In the reactively compatibilized blends, EPR-g-maleic anhydride (MA) has been used as the compatibilizer precursor. The MA group of the EPR reacts with the amino group of nylon forming a graft copolymer at the interface, which decreases the interfacial tension and suppresses the coalescence. In the case of uncompatibilized blends the final morphology is developed within 3-4 min of the mixing time in the DSM twin-screw mini extruder. The size of the dispersed phase in the uncompatibilized blends, as obtained in the Werner Pfleiderer twin-screw extruder and the DSM mini extruder, was found to be smaller than that obtained in the Haake Rheocord mixer on account of elongational flow occurring in the twin-screw extruder. In the case of the Werner Pfleiderer twin screw extruder, sampling was done at various points in order to understand the evolution of the phase morphology along the axis of the extruder. It has been found that the final morphology of the uncompatibilized blends in the Werner Pfleiderer extruder is controlled by the geometry of the die at the exit. In the case of reactively compatibilized blends, the morphology development in the DSM twin-screw mini extruder was so fast that the final morphology developed within 30 sec of mixing. This occurs because since the compatibilizer formed as a result of the reaction remains located at the blend interface, coalescence is substantially suppressed, and thereby the blend system rapidly attains a stable morphology. Finally the size of the dispersed phase and morphology development in reactively compatibilized blends in the three mixers were carefully studied and compared.