A study on the effects of chaotic mixer design and operating conditions on morphology development in immiscible polymer systems

Abstract

Self‐similar mixing structures, a novel feature of chaotic mixing, were generated in this study as precursor to an array of mixing microstructures, such as nested layers, elongated fibrils, droplets and their combinations in the blending of two immiscible polymers, polypropylene (PP) and polyamide‐6 (PA6). Simulations based on Newtonian flow model were used to compute Poincaré maps and stretching distribution as the tools for investigation of the effect of shear gap and chaotic mixing parameter, such as angular displacement per period (θ) of rotors, on the degree of mixing and morphology development in a batch chaotic mixing device. It was found that a value of θ = 1440° provided the conditions for fastest conversion of the PP‐phase into droplets for the same total strain. A 25% reduction in shear gap from 0.0127 m to 0.0095 m gave rise to much more uniform mixing of the components and led to faster conversion of the PP‐phase into droplets for the same value of θ and the same total strain. A very large fraction (>90%) of the droplets generated fell below the equilibrium size and were found to be much smaller than those produced by twin‐screw extrusion method. Polym. Eng. Sci. 44:407–422, 2004. © 2004 Society of Plastics Engineers.

Coalescence of immiscible polymer blends in chaotic mixers

“…Figure 9 presents representative steady streamline portraits and sketches of steady velocity profiles obtained by boundary integral method. 12 Note that due to steady motion of the rotors, a majority of fluid elements travel on "circular trajectories" (Figure 9a) around the rotors and do not mix well. These trajectories become chaotic with time-periodic speed variation as given in Eqs.…”

“…A more detailed description of the experimental setup is provided elsewhere. 12 Chaotic fluid element trajectories were generated using a sine waveform for rotor motion…”

“…It has been recently demonstrated that chaotic flows provide excellent means for producing fine scale dispersed phase morphology in the blending of immiscible polymers. [11][12][13][14][15][16] In these studies, repeated alignment, stretching and folding of the fluidic interfaces produce self-similar mixing structures which acted as templates for a series of morphological transitions similar to what was observed in nonchaotic flows, [2][3][4][5][6] for example, lamella, fibrils, droplets and their combinations, but with much smaller length scales. The chaotic fluid element trajectories also enhance transport of mass and energy [17][18][19][20][21][22] and improve distributive mixing in single screw extruders.…”

Study of Dynamic Flow and Mixing Performances of Tri-Screw Extruders with Finite Element Method

“…In addition, the chaotic mixing in the twin-screw or single-screw extruder has been carried out to reveal the stretching and folding actions, using Poincaré section, Lyapunov exponent, and so forth [8][9][10][11]. However, the studies of the tri-screw extruder are relatively limited due to its complex geometry and the short development time.…”

Morphology development and size control of poly(trimethylene terephthalate) nanofibers prepared from poly(trimethylene terephthalate)/cellulose acetate butyrate in situ fibrillar composites

“…Favis investigated the effect of mixing time on the morphology development of blends of polypropylene and polycarbonate and concluded that the most significant changes in morphology occurred during the first 2 min of mixing when melting and softening of the materials was also occurring [31]. Jana studied the effects of viscosity ratio and composition on development of morphology in chaotic mixing of polymers [32,33]. Sundararaj studied the effect of compatibilization and rotation rate on the morphology development of polymer blends.…”