Stages in spheronisation: Evolution of pellet size and shape during spheronisation of microcrystalline cellulose-based paste extrudates

Bryan, MP; Atherton, LN; Duffield, S; Rough, S.L.; Wilson, D.I.

doi:10.1016/j.powtec.2014.10.014

Cited by 17 publications

(27 citation statements)

References 19 publications

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“…This was confirmed in the current study by high speed video monitoring of the spheronisation step. Lau et al did not observe twisting, associated with the Baert et al [6] mechanism, whilst subsequent studies on similar MCC/water pastes by Bryan et al [1] indicated that the mechanism of fines specifically collecting at the waist (as described by Liew et al [7]) was not responsible for the transition from dumb-bell to more spherical shape.…”

Section: Introductionmentioning

confidence: 94%

Experimental validation of a dimensional analysis of spheronisation of cylindrical extrudates

et al. 2016

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Extrusion-spheronisation (E-S) is a widely used technique for the manufacture of pellets with high sphericity and narrow size distribution. A dimensionless framework for describing the evolution of pellet shape with spheronisation time is presented.The experiments employed a 45 wt% microcrystalline cellulose (MCC)/water-based paste, with up to 15 wt% calcium carbonate added to represent a 'hard' active pharmaceutical ingredient (API). The bulk yield strength of the paste was measured and found to increase with increasing carbonate content, which in turn led to higher extrusion pressures, longer spheronisation times and less spherical pellets for a given set of operating parameters. The pellet aspect ratio was found to increase in a linear manner with the logarithm of spheronisation time, progressing towards an asymptotic final value. This behaviour is compared with two simple models.The dimensional analysis of the pellet rounding stage identified the paste density and bulk yield strength as scaling quantities. The model borne from the dimensional analysis was validated and was found to be applicable to a second material (MCC/lactose/water).High speed imaging was also used to examine the collision behaviour of pellets during the breakage and rounding stages in spheronisation. The results confirmed that the rounding phase was the rate-determining step. The velocities of a number of tracked pellets were also quantified, and were consistently lower than the tip speed of the rotating friction plate. Bulk yield strength velocity factor, Equation (16) Pa (s m -1 ) m  Wall shear stress velocity factor, Equation (16) Pa (s m -1 ) n  p Friction coefficient, pellet-pellet - s Friction coefficient, pellet-spheroniser surface - Density kg m -3  Y0 Bulk yield strength at zero extrudate velocity, Equation (16) Pa  Y Bulk yield strength Pa  w  Wall shear stress Pa  0 Wall shear stress at zero extrudate velocity, Equation (16) Pa  Spheroniser rotational speed s -1 Acronymns API Active pharmaceutical ingredient E-S Extrusion-spheronisation MCC Microcrystalline cellulose PEEK Polyether ether ketone PIV Particle image velocimetry

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Section: Introductionmentioning

confidence: 94%

Experimental validation of a dimensional analysis of spheronisation of cylindrical extrudates

et al. 2016

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“…The average pellet surface tensile strength data in Figure 5 show a statistically significant effect of D on pellet tensile strength (F = 24.525, P = 0). The strengths of the pellets from D = 1.5, 2.0 and 2.5 mm extrudates are not statistically different (P(Welch test) = 0.054, P(Brown- 19 Forsythe test) = 0.129), while the strength of the pellets generated from D = 1.0 mm extrudates is significantly higher (see the Post Hoc Least Squares Difference (LSD) results in Table 6).…”

Section: Pellet Surface Tensile Strengthmentioning

confidence: 99%

“…This study extends earlier work [24] on the influence of extrudate diameter, D, and protuberance dimensions. Testing employed a 45 wt% MCC/water paste which has been employed previously as a model formulation to investigate E-S mechanisms [6,19,[24][25][26].…”

Section: Schmidt and Kleinebuddementioning

confidence: 99%

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Influence of the dimensions of spheroniser plate protuberances on the production of pellets by extrusion-spheronisation

Zhang

Wilson

et al. 2018

Advanced Powder Technology

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The influence of the dimensions of square-patterned pyramidal protuberances on a spheronisation plate on pellet yield, size and shape distributions, surface tensile strength and surface morphology was investigated using a 45 wt% microcrystalline cellulose/water paste.Tests were conducted using four extrudate diameters (1.0, 1.5, 2.0 and 2.5 mm) generated by screen extrusion and seven plate geometries, including a flat plate as a control. Geometrical analyses of the protuberance shapes provide some insight into the observed differences.Sharper protuberances reduced yield (promoting breakage and attrition) but tended to give narrower size distributions and less even pellet surfaces. The pellet yield for 1 mm extrudates was also subject to losses caused by fragments passing through the 1.0 mm gap between the plate and the spheroniser wall. Pellet tensile strengths were noticeably greater for 1.0 mm diameter extrudates, which is attributed to the greater extensional strain imparted on the paste during the extrusion step. For some geometries there is an optimal ratio of extrudate to protuberance dimensions.

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“…[4]. Since the pellets have a cylindrical shape at the beginning of the spheronization process and undergo different stages of deformation (cylindrical -dumbbell -spherical) during the rounding process [5][6][7], this contribution focuses on the influence of the particle shape on the particle dynamics. The simulation results provide information about the influence of the particle shape on the particle flow regime and the mixing of the particle torus, as well as the influence on the collision rates and forces.…”

Section: Fig 1 Spheronizer Geometry Used In the Simulationsmentioning

confidence: 99%

Effect of the particle shape on the particle dynamics in a spheronization process

Weis¹,

Niesing

Thommes

et al. 2017

EPJ Web Conf.

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Abstract. Spherical granules with a narrow size distribution are widely used in many pharmaceutical applications. Extrusion-spheronization is a well-established process to produce such pharmaceutical pellets. The cylindrical extrudates from the extrusion step are rounded in the spheronizer. The formation mechanisms inside of a spheronizer depend strongly on the particle dynamics. To describe the complex particle flow and interactions, the Discrete Element Method can be used. In our previous works the spherical particles during the last part of the spheronization process were studied. Since the pellets have a cylindrical shape at the beginning and undergo different stages of deformation during the rounding process, the objective of this study was the description of the influence of the particle shape on the particle dynamics. To predict the interactions of the pellets, their dominant plastic behaviour was described with an appropriate contact model and the material parameters were calibrated with compression and impact tests.

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Stages in spheronisation: Evolution of pellet size and shape during spheronisation of microcrystalline cellulose-based paste extrudates

Cited by 17 publications

References 19 publications

Experimental validation of a dimensional analysis of spheronisation of cylindrical extrudates

Experimental validation of a dimensional analysis of spheronisation of cylindrical extrudates

Influence of the dimensions of spheroniser plate protuberances on the production of pellets by extrusion-spheronisation

Effect of the particle shape on the particle dynamics in a spheronization process

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