Effect of addition protocol on mixing in miscible and immiscible polymer blends

Abstract

AbstractThe effects of the addition protocol are investigated for very‐low‐viscosity‐ratio model miscible and immiscible blends consisting of two polyethylenes (PE) and polystyrene (PS)/polyethylene (PE), respectively, are investigated. Miscible and immiscible blends with a matched viscosity ratio of 0.003 are compounded using three different addition protocols: simultaneous solids addition; sequential solids addition; and sequential liquids addition. These protocols correspond to addition of a solid additive to the feed hopper of an extruder; addition of a solid additive into the melting zone in an extruder; and addition of a liquid additive into the melting zone of an extruder. Both of these blends are shown to exhibit phase‐inversion‐like behaviors using a simultaneous solids addition protocol, regardless of concentration. Using either of the sequential addition protocols results in macroscopic segregation of the minor‐phase material to high‐shear‐rate regions of the mixer, delaying mixing. At long mixing times, however, all three protocols achieve a similar dispersed droplet morphology. Furthermore, the simultaneous solids addition protocol is shown to be the least energetically intensive, and the simultaneous solids requires the least amount of time of the three protocols to achieve maximum mixing torque for blends consisting of 20 wt% minor phase.