Simple and immediate quantitative evaluation of dispersive mixing

Pandey, Vivek; Chen, Tianke; Guo, Min; Maia, João M.

doi:10.1016/j.polymertesting.2020.106587

Cited by 3 publications

(2 citation statements)

References 21 publications

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“…A few authors have also proposed the use of mixing indices to straightforwardly characterize the extent of distributive or dispersive mixing, as these would facilitate direct comparisons between different operating conditions, screw profiles, and material properties. Average particle/droplet size relative to the initial size, number-average diameter [ 22 , 23 ], relative flow strength [ 24 ], shear stress distribution [ 25 , 26 ], and cumulative area ratio [ 27 , 28 ] have been routinely used as indicators of dispersive mixing, whereas Shannon entropy [ 29 ] was suggested as a measure of distributive mixing. Nevertheless, these indices require either lengthy experimental characterization or computationally demanding calculations.…”

Section: Introductionmentioning

confidence: 99%

On-Line Optical Monitoring of the Mixing Performance in Co-Rotating Twin-Screw Extruders

2022

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The use of real-time techniques to evaluate the global mixing performance of co-rotating twin-screw extruders is well consolidated, but much less is reported on the specific contribution of individual screw zones. This work uses on-line flow turbidity and birefringence to ascertain the mixing performance of kneading blocks with different geometries. For this purpose, one of the barrel segments of the extruder was modified in order to incorporate four sampling devices and slit dies containing optical windows were attached to them. The experiments consisted in reaching steady extrusion and then adding a small amount of tracer. Upon opening each sampling device, material was laterally detoured from the local screw channel, and its turbidity and birefringence were measured by the optical detector. Residence time distribution curves (RTD) were obtained at various axial positions along three different kneading blocks and under a range of screw speeds. It is hypothesized that K, a parameter related to the area under each RTD curve, is a good indicator of dispersive mixing, whereas variance can be used to assess distributive mixing. The experimental data confirmed that these mixing indices are sensitive to changes in processing conditions, and that they translate the expected behavior of each kneading block geometry.

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Section: Introductionmentioning

confidence: 99%

On-Line Optical Monitoring of the Mixing Performance in Co-Rotating Twin-Screw Extruders

2022

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“…The second is distributive mixing, whereby large strains are applied to the materials in order to spatially distribute the dispersed phase as homogeneously as possible in the matrix. [2][3][4][5] Extruders are generally used in the form of continuous mixers in polymer industry. The most widespread types of extruder are single-screw extruders (SSE), which typically are poor mixing devices but allow for large throughputs, and intermeshing co-rotating twin-screw (Co-TSE), which are very good mixing devices, but suffer from poor throughput by comparison to SSEs.…”

Section: Introductionmentioning

confidence: 99%

Comparative computational analysis of dispersive mixing in extension‐dominated mixers for single‐screw extruders

Pandey

Maia

2020

Polymer Engineering & Sci

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Enhanced dispersive mixing can be achieved by harnessing extensiondominated flows, because they are more efficient in agglomerate/droplet breakup than shear-dominated flows. Herein, we compare computationally the performance of two single-screw extrusion mixing sections with significant extensional flow components, the Chris Rauwendaal dispersive (CRD) mixer and the extensional mixing element (EME), recently proposed by the authors. Tapered slots in the CRD and hyperbolic contractions in the EME attempt to create extensional stresses through significant velocity gradients. Our studies confirm that EMEs are a better dispersive mixer than the CRD mixer, as they impose more intense and uniformly distributed extensional flow in a higher volume fraction of the material, and with less specific mechanical energy consumption. Overall, the EME design with a biaxial contraction was found to be the best dispersive mixer for single-screw extruders (SSE). The manuscript also summarizes all the existing dispersive mixers for SSE and ranks them relatively for their dispersive mixing capability.

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Dense nanolipid fluid dispersions comprising ibuprofen: Single step extrusion process and drug properties

Morrison¹,

Guo

Maia

et al. 2021

International Journal of Pharmaceutics

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Simple and immediate quantitative evaluation of dispersive mixing

Cited by 3 publications

References 21 publications

On-Line Optical Monitoring of the Mixing Performance in Co-Rotating Twin-Screw Extruders

On-Line Optical Monitoring of the Mixing Performance in Co-Rotating Twin-Screw Extruders

Comparative computational analysis of dispersive mixing in extension‐dominated mixers for single‐screw extruders

Dense nanolipid fluid dispersions comprising ibuprofen: Single step extrusion process and drug properties

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