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

Kaysan, Gina; Spiegel, Burkard; Guthausen, Gisela; Kind, Matthias

doi:10.1002/ceat.202000193

Cited by 10 publications

(16 citation statements)

References 21 publications

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“…Different aspects of contact crystallization of emulsions have been described in literature. A distinction can be made between investigations with superposition of primary and secondary nucleation under flow, [ 56,57 ] only secondary nucleation in flow fields, [ 29,58 ] and secondary nucleation without external flow (only Brownian motion). [ 2,59,60 ]…”

Section: Resultsmentioning

confidence: 99%

“…In a preliminary study, [ 29 ] the crystallization of emulsions was inline measured by NMR at a laminar Couette flow. A self‐made setup according to Morimoto et al [ 21 ] was used with a rotating outer cylinder.…”

Section: Introductionmentioning

confidence: 99%

“…A self‐made setup according to Morimoto et al [ 21 ] was used with a rotating outer cylinder. The shear rate in the experiments carried out by Kaysan et al [ 29 ] was limited to about 300 s −1 , and only laminar Couette flow could be realized. Nevertheless, the setup ensured stable and reproducible flow conditions at an exactly defined temperature and a well‐defined flow field.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, the setup ensured stable and reproducible flow conditions at an exactly defined temperature and a well‐defined flow field. [ 29 ] These experiences lead to the current study at technically relevant shear rates.…”

Section: Introductionmentioning

confidence: 99%

“…The nucleation efficiency

λ_{\sec}

[−] is introduced to quantify the crystallization efficiency. [ 29 ] If all collisions led to crystallization, the nucleation efficiency would be 1.

λ_{\sec} goodbreak= \frac{k_{coll, eff}}{β_{SL} n_{total}},

…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Contact‐mediated nucleation in melt emulsions investigated by rheo‐nuclear magnetic resonance

Kaysan

Schork²,

Herberger

et al. 2021

Magnetic Reson in Chemistry

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Increasing the efficiency of disperse phase crystallization is of great interest for melt emulsion production as the fraction of solidified droplets determines product quality and stability. Nucleation events must appear within every single one of the μm-sized droplets for solidification. Therefore, primary crystallization requires high subcooling and is, thus, time and energy consuming. Contact-mediated nucleation is a mechanism for intensifying the crystallization process. It is defined as the successful nucleation of a subcooled liquid droplet induced by contact with an already crystallized droplet. We investigated contact-mediated nucleation under shear flow conditions up to shear rates of 457 s À1 for a quantitative assessment of this mechanism. Rheo-nuclear magnetic resonance was successfully used for the time-resolved determination of the solids fraction of the dispersed phase of melt emulsions upon contactmediated nucleation events. The measurements were carried out in a dedicated Taylor-Couette cell. The efficiency of contact-mediated nucleation λ sec decreased with increasing shear rate, whereas the effective second order kinetic constant k coll,eff increased approximately linearly at small shear rates and showed a linear decrease for shear rates higher than about 200 s À1 . These findings are in accordance with coalescence theory. Thus, the nucleation rate is optimal at specific flow conditions. There are limitations for successful inoculation at a low shear rate because of rare contact events and at a high shear rate due to too short contact time.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…The nucleation efficiency

λ_{\sec}

[−] is introduced to quantify the crystallization efficiency. [ 29 ] If all collisions led to crystallization, the nucleation efficiency would be 1.

λ_{\sec} goodbreak= \frac{k_{coll, eff}}{β_{SL} n_{total}},

…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Contact‐mediated nucleation in melt emulsions investigated by rheo‐nuclear magnetic resonance

Kaysan

Schork²,

Herberger

et al. 2021

Magnetic Reson in Chemistry

Self Cite

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show abstract

Investigation of the surfactant distribution in oil‐in‐water emulsions during the crystallization of the dispersed phase via nuclear magnetic resonance relaxometry and diffusometry

Kaysan

Kräling

Meier³

et al. 2022

Magnetic Reson in Chemistry

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The crystallization of melt emulsions is of great interest to the food, cosmetic, and pharmaceutical industries. Surfactants are used in emulsions and suspensions to stabilize the dispersed phase; thus, questions arise about the liquid-liquid and solid-liquid interfaces of the droplets or particles and the distribution of the surfactant in the different phases (continuous and dispersed phase, interface). Nuclear magnetic resonance relaxation and diffusion measurements revealed that the internal and rotational mobility of surfactant molecules at the liquid-liquid interface decreases with increasing droplet sizes. Additionally, solid-liquid interfaces have fewer surfactants than liquid-liquid interfaces as a result of the desorption of the surfactant molecules during the crystallization of the droplets. Relaxation rates of surfactant molecules in aqueous solution as single molecules, micelles, and at the liquid-liquid and solid-liquid interface are analyzed for the first time.

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Chain Dynamics in a Polyelectrolyte Solution Under Shear: A Rheological NMR Investigation

Bartosch,

Kohn,

Scheler

2023

Appl Magn Reson

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Rheological nuclear magnetic resonance (NMR) has been applied to study the effect of shear on the chain dynamics in a solution of a linear poly(sodium 4-styrenesulfonate). Information on the chain dynamics of poly(sodium 4-styrenesulfonate) sheared in a narrow-gap concentric double cylinder cell is inferred from the NMR transverse relaxation T2 for a concentration in the semidilute-entangled and in the concentrated regime. In the semidilute-entangled concentration enhanced relaxation is observed. In the concentrated regime signatures of a loss of entanglements are seen with increasing T2 and a decreasing fraction of the polymer showing restricted motion. The effect is enhanced when the electrostatic interaction along the polymer chain is reduced by the addition of NaCl.

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

Cited by 10 publications

References 21 publications

Contact‐mediated nucleation in melt emulsions investigated by rheo‐nuclear magnetic resonance

Contact‐mediated nucleation in melt emulsions investigated by rheo‐nuclear magnetic resonance

Investigation of the surfactant distribution in oil‐in‐water emulsions during the crystallization of the dispersed phase via nuclear magnetic resonance relaxometry and diffusometry

Chain Dynamics in a Polyelectrolyte Solution Under Shear: A Rheological NMR Investigation

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