An investigation into the kinetic (sliding) friction of some tablets and capsules

Hancock, Bruno C.; Mojica, Nestor; St.John-Green, Kimberley; Elliott, James A.; Bharadwaj, Rahul

doi:10.1016/j.ijpharm.2009.09.038

Cited by 22 publications

(5 citation statements)

References 30 publications

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“…Further to the geometrical dimensions of tablets and the pan, other properties of the tablet and pan used as part of the simulation are listed in Table 1. The interaction parameters, especially the coefficient of friction, vary with the material type as reported by previous experimental studies (Hancock et al, 2010;Suzzi et al, 2012). Hancock et al (2010) suggested that the tablet-polymer/steel friction coefficient varies from 0.0 to 0.74 according to the material and surface properties while Suzzi et al (2012) showed that the coefficient of restitution between tablets and marble plate is 0.74 with a standard deviation of 0.03.…”

Section: Numerical Model Of In-line Measurementmentioning

confidence: 67%

A quantitative comparison of in-line coating thickness distributions obtained from a pharmaceutical tablet mixing process using discrete element method and terahertz pulsed imaging

Chen

Lin

Markl

et al. 2018

Chemical Engineering Science

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The application of terahertz pulsed imaging (TPI) in the in-line configuration to monitor the coating thickness distribution of pharmaceutical tablets has the potential to improve the performance and quality of the spray coating process. In this study, an in-line TPI method is used to measure coating thickness distributions on pre-coated tablets during mixing in a rotating pan, and compared with results obtained numerically using the discrete element method (DEM) combined with a ray-tracing technique. The hit rates (i.e. the number of successful coating thickness measurements per minute) obtained from both terahertz in-line experiments and the DEM/ray-tracing simulations are in good agreement, and both increase with the number of baffles in the mixing pan. We demonstrate that the coating thickness variability as determined from the ray-traced data and the terahertz in-line measurements represents mainly the intra-tablet variability due to relatively uniform mean coating thickness across tablets. The mean coating thickness of the ray-traced data from the numerical simulations agrees well with the mean coating thickness as determined by the off-line TPI measurements. The mean coating thickness of in-line TPI measurements is slightly higher than that of off-line measurements. This discrepancy can be corrected based on the cap-to-band surface area ratio of the tablet and the cap-to-band sampling ratio obtained from ray-tracing simulations: the corrected mean coating thickness of the in-line TPI measurements shows a better agreement with that of off-line measurements.

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Section: Numerical Model Of In-line Measurementmentioning

confidence: 67%

A quantitative comparison of in-line coating thickness distributions obtained from a pharmaceutical tablet mixing process using discrete element method and terahertz pulsed imaging

Chen

Lin

Markl

et al. 2018

Chemical Engineering Science

Self Cite

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show abstract

“…The interaction parameters, especially the coefficient of friction, vary with the material type, as reported by previous experimental studies (Hancock et al, 2010;Suzzi et al, 2012). Hancock et al (2010) suggested that the tablet-polymer/steel friction coefficient varies from 0.0 to 0.74 according to the material and surface properties. Suzzi et al (2012) showed that the coefficient of restitution between tablets and a marble plate is 0.74±0.03.…”

Section: Biconvex Flat Elliptic Starmentioning

confidence: 57%

“…The DEM simulation is implemented in LIGGGHTS 3.1.0 (Kloss et al, 2012) with classical contact mechanics -Hertz theory for the normal contacts (Johnson, 1985) and Mindlin theory for the tangential contacts (Mindlin, 1949). The interaction parameters, especially the coefficient of friction, vary with the material type, as reported by previous experimental studies (Hancock et al, 2010;Suzzi et al, 2012). Hancock et al (2010) suggested that the tablet-polymer/steel friction coefficient varies from 0.0 to 0.74 according to the material and surface properties.…”

Section: Biconvex Flat Elliptic Starmentioning

confidence: 99%

“…Suzzi et al (2012) showed that the coefficient of restitution between tablets and a marble plate is 0.74±0.03. In the current study, since the coating pan is not equipped with baffles, the coefficient of friction is set to the relatively higher value of 0.74, following Hancock et al (2010). However, it should be noted that the influence of interaction parameters, especially the coefficient of friction, on the tablet orientation and intra-tablet coating thickness distribution requires further investigation in future.…”

Section: Biconvex Flat Elliptic Starmentioning

confidence: 99%

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Asymptotic limits on tablet coating variability based on cap-to-band thickness distributions: A discrete element model (DEM) study

Chen

Elliott

2017

Chemical Engineering Science

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“…In applications in protective coatings, a high hardness and mar resistance are of great importance. In applications as coatings on objects, such as drug tablets (Hancock et al, 2010) or seeds (Steffen et al, 1999), friction and tack adhesion should be low to ensure ease of production and handling.…”

Section: Introductionmentioning

confidence: 99%

Environmental Effects on the Coefficient of Friction and Tack Adhesion of Formulated Waterborne Coatings

et al. 2022

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Waterborne coatings emit a low amount of harmful volatile organic compounds (VOCs) into the atmosphere compared to solvent-cast coatings. A typical waterborne formulation for agricultural applications consists of colloidal thermoplastic particles (latex) as the binder, a thickener to raise the viscosity, inorganic filler particles with a water-soluble dispersant, and a colloidal wax to modify surface properties. The formulations typically contain hygroscopic species that are potentially subject to softening by environmental moisture. The hardness, tack adhesion, and coefficient of friction of formulated coatings determines their suitability in applications. However, the relationship of these properties to the components in a coating formulation has not been adequately explored. Furthermore, the relationship between hygroscopic components and properties is an added complication. Here, we have characterized the hardness and tack adhesion of model formulated coatings using a single micro-indentation cycle with a conical indenter under controlled temperatures (above and below the glass transition temperature of a latex binder) and relative humidities. In parallel, we measured the coefficient of kinetic friction, μk, for the same coatings using a bespoke testing rig under controlled environmental conditions. Across a range of temperatures, RH and compositions, we find an inverse correlation between the coating hardness and μk. Any correlation of μk with the roughness of the coatings, which varies with the composition, is less clear. Formulations that contain wax additives have a higher μk at a low RH of 10%, in comparison to formulations without wax. For the wax formulations, μk decreases when the RH is raised, whereas in non-wax formulations, μk increases with increasing RH. Wax-containing coatings are hydrophilic (with a lower water contact angle), however the wax has a lower water permeability. A lubricating layer of water can explain the lower observed μk in these formulations. The addition of wax is also found to planarize the coating surface, which leads to higher tack adhesion in dry coatings in comparison to coatings without wax. Greater adhesive contact in these coatings can explain their higher friction. Our systematic research will aid the design of seed coating formulations to achieve their optimum properties under a wide range of environmental conditions.

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An investigation into the kinetic (sliding) friction of some tablets and capsules

Cited by 22 publications

References 30 publications

A quantitative comparison of in-line coating thickness distributions obtained from a pharmaceutical tablet mixing process using discrete element method and terahertz pulsed imaging

A quantitative comparison of in-line coating thickness distributions obtained from a pharmaceutical tablet mixing process using discrete element method and terahertz pulsed imaging

Asymptotic limits on tablet coating variability based on cap-to-band thickness distributions: A discrete element model (DEM) study

Environmental Effects on the Coefficient of Friction and Tack Adhesion of Formulated Waterborne Coatings

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