Optimization of the compatibilizer concentration in polymer blends has generally been achieved through an indirect correlation with property improvements. In this article the evolution in particle size with percent interfacial modifier (emulsification curve) is used to quantitatively assess the state of the interface under a wide range of processing conditions in ABS/polyamide-6 (nylon-6) blends. This type of dependence can yield important information concerning the state of the interface of a given blend, including the concentration of compatibilizer necessary for interfacial saturation. To illustrate the applicability of an emulsification curve to polymer processing equipment, a comparison is made between the twin-screw extruder and the single-screw extruder. In order to simulate a wide processing performance range no additional mixing devices were used to enhance mixing on the single-screw extruder. The twin-screw extruder therefore represents the case of good mixing and the single-screw extruder represents that of poor mixing. Finally, for the good mixing case, the impact strength has been analyzed in order to observe its behavior at the critical concentration for interfacial saturation as well as the effect of dispersed phase composition. The size of the dispersed domains reveals important differences between the compounding effects of the single-screw as compared to the twin-screw extruder. A compatibilizing agent renders such a blend more homogeneous by reducing the particle size of the dispersed phase. It was also found for the single-screw extruder that the interface is not saturated and the phase size equilibrium value is not obtained even at high levels of interfacial modifier. The higher efficacy of the twin-screw extruder in migrating the modifier to the interface is clearly demonstrated through the use of the emulsification curve. The impact strength of material prepared by twin-screw/injection molding shows a significant increase at a modifier concentration, which correlates well with the critical concentration for interfacial saturation of interfacial modifier from the emulsification study. The impact strength of an optimally compatibilized system as a function of dispersed phase composition displays a maximum impact strength around 50% ABS in the co-continuous morphology region.