Influence of Shear Flow on the Crystallization of Organic Melt Emulsions – A Rheo‐Nuclear Magnetic Resonance Investigation

There is a need to better understand the influence of shear flow on the crystallization of a molten oil phase in an oil/water emulsion due to its high relevance for industrial processes. The present study focuses on the influence of laminar shear flow on the crystallization kinetics of polydisperse n‐hexadecane‐in‐water emulsions. The investigation was carried out by rheo‐nuclear magnetic resonance (NMR) spectroscopy in a Taylor‐Couette geometry. An accelerating impact of the shear rate on the overall crystallization kinetics was verified. This effect stems from an increase of the collision frequency of already crystallized droplets with not yet crystallized droplets. Nevertheless, the collision efficiency decreased with higher shear rate. Collision‐induced nucleation was utilized to accelerate crystallization kinetics, avoiding energetically unfavorable low process temperatures. An increase of crystallization rate with shear rate, yielding higher final solid fractions, was determined. Not every solid‐liquid contact results in the crystallization of the liquid droplet, as the collision efficiency decreased with increasing shear rate.