Progressive morphology development to produce multilayer films and interpenetrating blends by chaotic mixing

Abstract

Chaotic mixing of immiscible binary components was recently used in a continuous flow process to obtain extruded films with very many internal layers. Where interfacial tension is small, individual layer thicknesses can be only tens of nanometers and many thousands of continuous or broken layers can be formed. Such materials are both novel and potentially important. In this study, multilayer film formation and breakup were investigated systematically by using a batch chaotic mixer to better understand the more industrially relevant continuous flow counterpart. Polystyrene (PS) and low-density polyethylene (LDPE) were used as a model binary system with appreciable interfacial tension such that comparatively thicker layers and larger breakup bodies were formed and more readily examined. The multilayer film morphology developed progressively as chaotic mixing continued and was thereby amenable to control and optimization with regard to layer thickness and number. Blends with single or dual phase continuity and structured droplet distributions were found to be important derivative morphologies upon layer breakup.

Smart blending technology enabled by chaotic advection

“…The modeling results in Fig. 7 and experimental findings 31,46,48 show that incipient, developed, and fragmenting interpenetrating blend morphologies are all obtainable in extrusions, for example. Each may have differing properties.…”

“…1. In effect, both Polymer A and B are folded about each other 46 although layering may be most visually apparent in the minor component. The in situ layering and progressive morphology development in the smart blender resulting from chaotic advection are represented in Fig.…”

“…26 In contrast, LDPE layers of 1-4 µm form in polystyrene where σ ∼ = 4.5 dyn/cm and C µ = 0.07. 46 Based on these and other studies, effective operation at the low shear conditions considered to date (i.e., < 10 s −1 ) can be achieved in polymer combinations having small interfacial tension (σ < 5 mN/m) and viscosity ratios of 0.05 < C µ < 12. Where the minor component is a masterbatch consisting of the matrix polymer and solid additive, the desirable viscosity ratios also apply.…”

Coalescence of immiscible polymer blends in chaotic mixers

“…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.…”

Entropy Time Evolution In A Twin-flight Single-screw Extruder And Its Relationship To Chaos

“…Ottino [7][8][9] has studied extensively the role of chaotic flows on mixing coining the concept of chaotic mixing. Zumbrunnen [10,11] was first to perform chaotic advection studies of polymer blends and composites.…”