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Characterising powder flowability can be a challenge if only a small quantity of samples is available, e.g. pharmaceutical formulations. The paper focuses on a new method for assessing powder flowability based on physical properties and cohesiveness of particles using a few grams of powders. The technique applies Bond number to represent powder cohesiveness, which detects particle adhesion at median particle size using a mechanical surface energy tester developed at the Wolfson Centre. To establish the method, correlations between the Bond numbers and the flow functions of several powders measured on a shear cell tester have been explored empirically. With the correlations, a prediction model has been developed not only for powder flow functions but also for other flow properties such as compressibility, internal friction angles and true friction angles. This investigation has been undertaken using a wide range of materials from free-flowing to very cohesive for the method establishment and a group of different types of materials for a blind validation of the method. The methodology shows promising results for powder flowability prediction and other flow properties such as compressibility and internal friction angles. The validation results show a good agreement against the results measured using a shear cell tester.

Flowability parameters of powders measured by a shear cell is expected to depend on shear cell size, but details of that effect are lacking. In this work, we have systematically evaluated this using a number of powders under three preshear normal stresses using a ring shear tester. The flowability index (ffc) of a limestone powder (BCR 116) exhibited relatively small differences when measured on three shear cells of different sizes, S (~9.5 cm3) 22 μm was more than 15% higher using S than M. Large differences between data from M and L were found for powders with a median particle size >125 μm. Therefore, one must exercise caution when comparing flow properties of powders characterized using different shear cells.

Background Artificial meat offers a potential solution to consumer demand for meat, given global environmental concerns, public health problems, sustainability, and animal welfare problems. Although artificial meat may supplement or even replace traditional meat, it is still a challenge to reproduce muscle tissue's hierarchical structure. Scope and approach This review focused on the research history of artificial meat, the current technological challenges and possible solutions, and analyzed consumer attitudes toward artificial meat. Key findings and conclusions: With the rapid development of tissue engineering and bioreactor engineering, the new technologies for cultured meat have been continuously developed and improved. Extrusion, shear cell, and spinning are the main techniques for plant-based meat and its market has been expanding. Consumer attitudes toward cultured and plant-based meat vary by demographics and across cultures. There are some problems still needed to be overcome, including technology barriers and sensory, nutritional, health, and safety challenges in further developing the alternative meat market.

Nowadays, a growing offering of plant-based meat alternatives is available in the food market. Technologically, these products are produced through high-moisture shear technology. Process settings and material composition have a significant impact on the physicochemical characteristics of the final products. Throughout the process, the unfolded protein chains may be reduced, or associate in larger structures, creating rearrangement and cross-linking during the cooling stage. Generally, soy and pea proteins are the most used ingredients in plant-based meat analogues. Nevertheless, these proteins have shown poorer results with respect to the typical fibrousness and juiciness found in real meat. To address this limitation, wheat gluten is often incorporated into the formulations. This literature review highlights the key role of wheat gluten in creating products with higher anisotropy. The generation of new disulfide bonds after the addition of wheat gluten is critical to achieve the sought-after fibrous texture, whereas its incompatibility with the other protein phase present in the system is critical for the structuring process. However, allergenicity problems related to wheat gluten require alternatives, hence an evaluation of underutilized plant-based proteins has been carried out to identify those that potentially can imitate wheat gluten behavior during high-moisture shear processing., This research was funded by EIT Food RIS Talents Fellowship (KAVA #20272).

The design of new technology for processing and manufacturing particulate products requires understanding granular rheology over a broad range of conditions. Powders display a complex behaviour due to their ability to rearrange under stress, and as a result, granular flow is generally classified into three flow regimes, namely a quasi-static regime dominated by frictional contacts, an inertial regime dominated by collisional and kinematic stresses and an intermediate regime where the three sources of stress are important to establish a stress-strain rate relationship. Characterisation of the flowability is generally restricted to the flow initiation in quasi-static regime, even if, transition into inertial conditions is very common in practical applications involving the control of dense flows, such as powder handling, particle formation processes or additive manufacturing. This work presents a critical review of available techniques to characterise the departure from the quasi-static regime into an intermediate flow. We revise the application of shear cells and present different strategies to modify classic devices with external actuation, such as aeration, to operate at higher inertial numbers. We pay particular attention to innovative designs using aerated Couette flow configurations, highlight the complexity in the standardisation and the challenges in advancing towards a universal model.

A novel device has been developed for continuous shearing and repeated impact of granules in order to simulate granule attrition and dust formation under realistic plant conditions of mechanical stresses, shear strains and strain rates. The device subjects the granules to multiple impacts at a range of velocities prevailing in typical process plants, and to shear deformations using two rollers with an adjustable gap to simulate the level of shear stresses and strains experienced during bulk motion, e.g. discharge from silos onto conveyor belts, etc. In this paper, the device operation and tests carried out to determine the settings required for attaining a desired impact velocity and shear strain rate are described. Subsequently, the extent of breakage of the granules is determined for the specified settings and the results are compared with data obtained by more established methods, e.g. annular shear cell and single particle impact tests.

In granular flows, particles can mix or segregate owing to their difference in size/density. This behaviour is commonly understood as a size- or density-driven segregating flux at the macro scale and has been studied before in systems of shear cell and chute. This work aims to model the segregation in practical systems with complex geometries and flow modes, by coupling the fundamental flow rheology and the convection-diffusion-segregation transport equation. The model is validated against experimental measurements and discrete element simulations in various flow scenarios, shown able to capture the notable characteristics of particle segregation reported, such as the core of small particles in a rotating drum. The predictions can overall match the benchmark tests although the quantitative accuracy still varies with cases, indicating the need for further study. The proposed approach, not limited by operational or geometrical conditions, provides a useful tool for the design and control of mixing processes.

The aim of this study was to compare the bulk lactose flow behavior with a defined fraction with smaller particles obtained by sieving from the bulk lactose and to evaluate the effect of a glidant addition on both samples. These powders showed, in a previous work, similar flow indexes (ffc) that motivated the addition of colloidal silicon dioxide in order to observe if there were any changes in their flow behaviors. To evaluate this effect on the diluent flow behavior, the methods described in the European Pharmacopeia were used. The results obtained from conventional methods and shear cell methods (using the Powder Flow Tester) were compared, and they showed evident differences in the bulk and tapped densities values and flow classifications. The lactose monohydrate (FTotal) and lactose with particles smaller than 63 μm (F

Dynamic avalanche testing is a newer method useful even with cohesive powder samples. To evaluate flow properties of pharmaceutical powder excipients, break energy (BE) is introduced as a new promising avalanche parameter. Conventional pharmacopoeial methods and an annular shear cell were utilized to characterize 23 pharmaceutical powder samples including binary mixtures. Subsequently, rotating drum avalanching was studied to better understand behaviour of powders. A good linear regression between the energy to break a powder avalanche and powder cohesion with R2 = 0.823 was detected. The relationship between BE and the flow function value, estimated by shear testing, allowed to identify two samples with excellent flow functions: Cellets 100 and Neusilin US2. The latter sample also had very low BE although the mass flow rate was the poorest observed out of 23 samples. Therefore, the BE from avalanching testing seems to be a sensitive measure of cohesion and flow function behaviour.

Knowledge of the rheological behavior of saturated particulate networks is crucial for every process in which a particulate network is built-up, dewatered, or transported, as in a decanter centrifuge. However, difficulties arise as to how to characterize the material properties. Thus far, no standardized method or measurement device has prevailed. In this work, the requirements for a useful device are discussed, followed by the design of a modified shear cell for a Schulze ring shear tester RST-01.pc and its measurement procedure. Shear experiments under normal load with different sediments consisting of inorganic and organic particles whose material properties strongly affect the rheological behavior were performed. The results demonstrate the potential of the modified shear cell. Furthermore, current challenges in characterization are discussed. The characterization possibilities of the developed shear cell are a further step toward understanding the rheological behavior of liquid-saturated particulate networks.

Shear cell tests have been conducted on twenty different lactose powders, most of which commercially available for oral or inhalation purposes, spanning a wide range of particle sizes, particle morphologies, production processes. The aims of the investigation were: i) to verify the reliability of the technique in evaluating and classifying the flowability of powders; ii) to understand the connection between the flowability of a powder and the morphological properties of its particles; iii) to find a general mathematical relationship able to predict the yield locus shape given the particle size, shape and consolidation state of a lactose powder. These aspects and their limitations are detailed in the manuscript together with other interesting findings on the stick-slip behavior observed in most of the lactose powders examined.

Discrete Element Method (DEM) simulations coupled with shear cell experimental results have been used to investigate the flow behaviour of a dry particle assembly of glass beads in the quasi-static regime. 10 Experimental studies have been undertaken using an FT4 powder shear cell apparatus, in parallel with extensive DEM simulations of both homogeneous simple shear and the FT4 shear cell itself. The findings show that it is not possible to accurately predict the bulk friction coefficient with homogeneous simple shear simulations unless both rolling and sliding friction are considered. There are, however, multiple pairs of sliding and rolling friction coefficients which can reproduce the experimental bulk friction coefficient. Sliding 15 test experiments were conducted to yield the coefficient of sliding friction, and hence minimise the set of potentially correct pairs. Simulations of the full FT4 shear cell with two different calibration pairs, along with a pair without rolling friction, were then undertaken to understand the effect of their selection on realistic wall-bounded shearing conditions. Discrepancies were mainly found in the obtained radial contact number and velocity profiles, with increasing friction coefficients - particularly sliding friction - found to in20 hibit packing and particle velocity in the shear deformation zone. Comparison between homogeneous simple shear and shear cell simulation results showed a significant effect of the wall on the obtained force network, with almost a complete absence of the weakest structures which were seen supporting the strong structures in the simple shear scenario.

This paper investigates the Angle of Repose (AoR) of powder materials with respect to their morphological and rheological properties. Glass beads, sand, flour and semolina of different particle sizes were used as the experimental materials. The investigated material was analysed with respect to particle shape and size. The rheological properties of the material were obtained by a shear cell test. The AoR was analysed in terms of cohesion, bulk density, particle size and circularity. More cohesive materials such as the flour samples exhibited the largest AoR > 40°, indicating their poor flowability. Glass bead samples with a high circularity value had significantly lower AoR than the flour. The Angle of Internal Friction values were not dependent on those of the AoR. Using a dimensional analysis, a mathematical model was developed to determine the AoR values based on the material properties. By the application of this model, highly accurate calculation of the value of AoR is made possible.

At moderate stresses, shear cells are the preferred method of powder flow measurement. However, several industrial processes operate at low stresses, where the determination of unconfined yield strength by the shear cell technique may be inconsistent, or found not to correlate with observed behaviour. Alternatively, ball indentation can be used, which directly measures hardness; related to unconfined yield strength by the constraint factor. However, it is not known how constraint factor is influenced by particle properties. Here, ball indentation and shear cell methods are applied for glass beads of various size distributions, and the influence of particle size distribution on the constraint factor is explored. The constraint factor is shown to be independent of the pre-consolidation stress, though reduces as the d10, d50 or d90 are increased. Unconfined yield strength inferred from indentation measurements suggest that extrapolation of shear cell data to low stresses overestimates the unconfined yield strength

We have studied experimentally the effect of the water content on the drag force applied by a wet granular system on a probe moving through it at constant velocity. Similar to what has been observed for dry granular systems, the drag force is found to be independent of the velocity of the probe. By comparing our result with the dry case, we have shown that three main physical mechanisms occur: cohesion (consequence of capillary forces), contact lubrication and dilatancy induced by cohesion. The influence of the latter mechanism prevails in our system and the relative influence of the two former ones is found to depend on grains' characteristics. At important water contents, the granular system may become heterogeneous and its structure is modified by the motion of the probe. Our analysis is strengthened by shear cell experiments which also point out the importance of the geometry of the system on the effect of the water content.

Simultaneous measurements of interdiffusion and intrinsic diffusion coefficients in liquid Sn-Pb were performed using the shear cell method and a stable density layering. The binary diffusion couples of Sn-Pb and Sn0.6Pb0.4-Sn0.4Pb0.6 were used in two experiments with the average molar fraction of diffusion couples NSn = 0.5. The concentration dependency of the interdiffusion coefficient was confirmed to exhibit a downward convexity through the comparison of the interdiffusion coefficients. However, the Boltzmann–Matano method reveals a diminished influence. The sample measurements of the intrinsic diffusion coefficients of a diffusion couple of pure metals demonstrate a dependency on concentration. On the other hand, the difference of diffusion coefficients was small in a diffusion couple of alloys. The difference between the values calculated by fitting the error function based on the superposition of fluxes and by the conventional analysis methods was small. We propose that a reasonable intrinsic diffusion coefficient can be calculated using the superposed equation of error function. The theoretical interdiffusion coefficients were calculated by substituting the measured intrinsic diffusion coefficients into the Darken’s equation and comparing the results with the measured values. As a result, the difference between the theoretical and measured interdiffusion coefficients is not very large.

Powder flow and packing behavior are among other factors determined by particle friction, which is traditionally measured in shear cells as the angle of internal friction (AIF). Considering that an AIF at a normal stress should be comparable to friction during tapping consolidation, this work aims at whether dynamic consolidation under gravity can be used to estimate an AIF. Powder consolidation by controlled tapping was studied for seven commercially available types of lactose. A porosity factor was determined, and values were compared with the AIF obtained from Jenike shear cell measurements. Plotting porosity factor vs. number of applied taps provided an estimated angle of internal friction (AIFE) that was obtained from the slope of a linear relationship. A significant linear correlation (r = 0.825; p = 0.0223) was evidenced between AIFE and those AIFJ estimated from linearized yield locus measurements of using the Jenike shear cell. The good linear correlation between the angle of internal friction estimated from dynamic powder consolidation and the internal friction obtained by a shear cell is of high practical relevance. The latter shear cell behavior is only occasionally studied in the pharmaceutical industry, whereas dynamic powder tapping is a standard analysis.

Discrete Element Method (DEM) simulations of elongated (i.e. needle-shaped) particles breakage in a shear field confined between two parallel plates, in analogy with processes occurring in a powder shear cell tester, were carried out. Effects of particle strength, shear rate and the compressive stress were investigated. The breakage patterns occurring in a layer of particles due to compressive and shearing stress fields are analysed in detail and compared. The results of these computational experiments reveal that when the course of particle breakage is represented in the mean particle length vs. polydispersity diagram, the breakage patterns for slow shearing and compression follow the same path that is close to the path constructed for an idealized breakage scenario, while curves for fast shearing deviate from the scenario towards higher polydispersities.

Purpose The purpose of this work is to demonstrate a process for the alteration of the shape of needle shaped crystals of an active pharmaceutical ingredient (API) using a combination of wet milling and temperature cycling. The effect upon powder handling metrics of the shape alteration approach was quantified and the impact upon a subsequent roller compaction process step demonstrated. Methods Particle shape was altered through a combination of wet milling and temperature cycling. Image analysis was used to measure the length and width of the needle shaped particles. Powder handling was quantified using shear cell and bulk density measurements. Roller compaction trials were used to demonstrate improvements in processability. Results Particle width and length could be altered independently of each other with appropriate application of wet milling and temperature cycling. Powder handling metrics were greatly improved by the shape alteration. A partial least square model was developed to help explain the link between particle properties and powder handling metrics. Conclusions A process for altering the shape of needle shaped particles was developed. This process manifested in an improvement in both powder handling metrics and the processability of the powder as demonstrated by roller compaction.

By utilizing the shear cell technique and achieving stable density layering with the addition of an alloying element Bi, the self-diffusion coefficients of liquid Sn were measured on the ground at 573 K, 773 K, and 973 K (300 °C, 500 °C, and 700 °C). Moreover, the impurity diffusion coefficients of Bi in the liquid Sn were simultaneously measured, to confirm the suppression of natural convection. From the experimental results, natural convection was confirmed to be suppressed, given that the impurity diffusion coefficients of Bi were in good agreement with the microgravity reference data. Upon changing the amounts of added Bi within 5 at. pct Bi, the self-diffusion coefficients of liquid Sn did not vary significantly. Moreover, the SnBi system within 5 at. pct Bi can be regarded as a dilute solution by calculating the activity of Sn in the SnBi system beforehand. The self-diffusion coefficients of the liquid Sn were in good agreement with the power law of temperature dependence from the microgravity reference data. After confirming the suppression of natural convection and that the SnBi system is a dilute solution, the self-diffusion coefficient of liquid Sn was determined as 5.00 ± 0.16 × 10−9 m2 s−1 at 773 K (500 °C). The effectiveness of the experimental method used in this study for the measurement of the self-diffusion coefficients was confirmed, under the condition that the liquid system could be regarded as a dilute solution.

We studied the influence of nanoparticles with different surface modifications on the interfacial tension and relaxation of model polymer blend after cessation of different strains. The droplet retraction experiments were carried out on a model system composed of polydimethylsiloxane (PDMS) as the suspending fluid and polyisobutylene (PIB) as droplet at room temperature in the presence of hydrophobic and hydrophilic nanosilica. Different weight fractions of particles were dispersed in the PIB droplet before forming a dispersed droplet by using a microsyringe in shear cell. We found that applied strain, nanoparticle concentration and their thermodynamically preferred localization affect both nominal interfacial tension and droplet retraction process. By addition of nanoparticles at a concentration as low as 0.2%wt, the nominal interfacial tension decreases from 3.12 ± 0.15 mN/m for neat PIB-PDMS interface depending on the surface characteristics of nanosilica. Hydrophilic nanosilica has the most effect on nominal interfacial tension and decreases it as low as 0.2 ± 0.21 mN/m at 1 wt.% loading under a strain of 7. The results show that the retraction process in this system is mainly controlled by interfacial phenomena rather than bulk rheological properties. Additionally, the shape evolution of droplets changes and the retraction rate slows down in the presence of nanoparticles.

In order to investigate the characteristics of force chains in a granular flow system, a parallel plate shear cell is constructed to simulate the shear movement of an infinite parallel plate and observe variations in relevant parameters. The shear dilatancy process is divided into three stages, namely, plastic strain, macroscopic failure, and granular recombination. The stickslip phenomenon is highly connected with the evolution of force chains during the shear dilatancy process. The load–distribution rate curves and patterns of the force chains are utilized to describe the load-carrying behaviors and morphologic changes of force chains separately. Force chains, namely, “diagonal gridding,” “tadpole-shaped,” and “pinnate” are defined according to the form of the force chains in the corresponding three stages.

This study examined the feasibility of combining data from different powder flow testers to determine the flow function characteristics of pharmaceutical powders. The Brookfield PFT and Freeman FT4 can measure flow function over different scales of consolidation load but were found to be most complementary with CRM limestone powder and lactose. The brittle behaviour of Easytab particles at higher loads made obtaining repeatable results with the FT4 challenging. By using the method of Wang et al., where the flow function coefficient ffc is plotted against the dimensionless cohesion C* (measured cohesion Ta divided by the initial compaction I), a plot was formed which could be used to predict the behaviour of other systems, which compared well with previous studies.

This review discusses the use of starch in plant-based meat replacing products. Starch is often added to meat and meat replacing products as a functional ingredient. The function of starch in those applications is investigated to be able to describe how it affects the production and structuring process as well as product properties. Often modified starch is used in these products, because of its improved functionality compared to native starch. Next to that, starch can also be present in meat replacing products as part of other ingredients, for example, when using legume or cereal meals or concentrates. It is discussed if this endogenous starch can have similar functionality and if not, whether it can be modified in a similar way as industrially modified starch. A new perspective on endogenous starch is proposed, demonstrating options for in situ modifications and promoting the use of less-refined and therefore more sustainable ingredients in fibrous meat replacing products.

Dense granular flow can exhibit various unique behaviours as compared to those of common solids, liquids and gases, an example being the banding phenomenon occurring in sheared granular materials. The shear band is universal in various granular systems and represents a significant challenge in physics. Using a continuum-based Eulerian finite element method, this paper presents an investigation of the wide band phenomenon of granular material within a rotating split-bottom shear cell. It is shown that different patterns and geometrical profiles of the band observed in previous experiments can be well reproduced. The ratio of filling height to split radius is found to control both the band transition and band geometry. A parametric study shows that the obtained band varies remarkably with the rotational rate of shear cell and dilation of granular material, indicating the importance of inertial effect and dilation in the band formation and thus, the necessity of a dynamic modelling approach. The effects of other material properties including the internal friction angle and cohesion are also examined.

In this work, three different shear testers—the Jenike shear cell tester, the Schulze ring shear tester, and the Brookfield powder flow tester—were compared in terms of the raw shear stress time series, yield loci points, angle of internal friction, cohesion, and unconfined yield strength. The three different powders of dolomitic lime, calcium lactate, and calcium carbonate were used for these comparisons. These three powders were characterized into different flowability classes using the Jenike classification, wherein dolomitic lime falls into the cohesive range, calcium lactate falls into the free-flowing range, and calcium carbonate falls into the very cohesive range. Results showed that the best agreement between the testers was found with moderately cohesive powders such as dolomitic lime. Furthermore, the free-flowing material tends to produce more consistent data between the three testers in terms of shear stresses and yield loci. It should be noted that the pre-shear data of free-flowing powder obtained by the Jenike shear cell must be appropriately interpreted. The largest differences between the testers are found with calcium carbonate, which is a highly compressible powder. The ways in which a high powder compressibility can differently affect the results obtained with the different testers were discussed.

This article belongs to the Special Issue Rheology and Texture Interacction and Their Relationship with Sensory Perception., This study assessed the usefulness of the miniature Kramer shear cell to determine relevant instrumental parameters of solid foods and bolus counterparts, examining their relationships with oral processing behaviors to obtain greater knowledge about the texture perception process. Six solid foods with different textural properties were tested. Bolus mechanical properties were also determined by means of cone penetration tests and rheological measurements, and their particle size distributions by sieving. Oral processing behavior (chewing time, number of chews, chewing rate, eating rate) and food saliva uptake (SU) of a young volunteer and a panel of 39 untrained participants were analyzed. The Kramer mechanical properties were very suitable for detecting different levels of food and bolus textural hardness and fracturability and the associated degrees of fragmentation achieved during mastication. Chewing time and number of chews were highly correlated with Kramer food and bolus mechanical properties for the single subject and for the panel’s oral processing behaviors. For the single subject, SU and eating rate also showed strong correlations with food and bolus mechanical properties, unlike chewing rate and food moisture content (FMC). In contrast, eating rate, FMC, and SU did not vary with the oral activities of the panel.

The powders used in the production of solid dosage forms must have ability to flow that allows their industrial processing. Although this property has been studied for most of the powders, in this study non-expected flow behaviors were observed for the model excipient used, Microcrystalline Cellulose (MCC). Several fractions with different sizes were fractioned by sieving of the model excipient and its flow behaviors were analyzed by different methods. The shear cell results showed an increase of the flowability index (

Explore the impact of powder flow properties such as flow energy and compressibility on the performance characteristics of foundation powders such as cake strength and pay-off.FT4 Powder Rheometer from Freeman Technology was utilized to explore various powder compositions. The three major tests performed were flowability test, compressibility test and shear cell test.The results highlight that the sample which has higher compressibility has the better cake strength, and the sample which requires lower total energy has better pay-off. Particles or samples with lower total flow energy, should have easier flow, therefore, should have better pay-off. Samples and components with higher compressibility, should hold the structure better, therefore, should have better cake strength. Talc has the highest compressibility and lowest flow energy. Foundation sample 5 has the highest concentration of talc and also has the best performance.The lower the total flow energy, the easier it is for the powder to flow, and have better pay-off. Powder compressibility correlates with cake strength which means that a sample with better compressibility consequently has the better cake strength. Samples 5 and 10 require less total flow energy, have lower shear stress, and higher compressibility, therefore, have better final performance. Both samples 5 and 10 have higher talc concentrations compared to other formulations.Explorer l'impact des propriétés d'écoulement des poudres, comme l'énergie d'écoulement et la compressibilité, sur les caractéristiques de performance des fond de teint en poudres comme la quantité de poudre prélevée (rendement) et la résistance au choc. MÉTHODÉS: Le rhéomètre à poudre FT4 de Freeman Technology a été utilisé pour explorer différentes compositions de poudre. Les trois principaux tests effectués étaient le test de fluidité, le test de compressibilité et le test des cellules de cisaillement. RÉSULTATS: Les résultats mettent en évidence que l'échantillon qui a une compressibilité plus élevée a la meilleure résistance au choc, et l'échantillon qui nécessite une énergie totale inférieure aura un meilleur rendement. Les particules ou les échantillons avec une énergie de flux totale inférieure, devraient avoir un écoulement plus facile, par conséquent, devraient avoir un meilleur rendement. Les échantillons et les composants avec une compressibilité plus élevée devraient mieux maintenir leur structure, par conséquent, devraient avoir une meilleure résistance au choc. Le talc a la compressibilité la plus élevée et l'énergie d’écoulement la plus faible. Le fond de teint 5 a la plus forte concentration en talc et présente également les meilleures performances.Plus l'énergie d'écoulement totale est faible, plus la poudre pourra s'écouler et aura un meilleur rendement. La compressibilité de la poudre est corrélée à la résistance au choc, ce qui signifie qu'un échantillon avec une meilleure compressibilité a par conséquent la meilleure résistance au choc. Les échantillons 5 et 10 nécessitent moins d'énergie d'écoulement totale, ont une contrainte de cisaillement plus faible et une compressibilité plus élevée, donc de meilleures performances finales. Les échantillons 5 et 10 ont des concentrations de talc plus élevées que les autres formulations.

Multiple pharmaceutical powder processes operate at stresses lower than utilized in typical lab-scale shear cell testing. To bridge this gap, we developed a method to determine intrinsic powder flow properties, in particular, flow function (FFc), under such low stresses. A simple, commercially-available flow-through-orifice device (Flodex™ apparatus) was selected. By developing a theoretical framework using Jenike’s radial stress field analysis, the major principal stress and FFc of the tested powder can be derived from the otherwise empirical “Flodex” experiment. This method was applied to 10 distinct pharmaceutical powders. The major principal stresses associated with the test were estimated to be in the order of 100 Pa, significantly lower than what is achievable using shear cell-based methods. The resulting FFc values are generally consistent with the data extrapolated from ring shear testing. We showed that for pharmaceutical powders, FFc decreases with decreasing consolidation stress, but the values are always greater than 1. Therefore, the threshold for poor/acceptable flowability (by FFc) should be used with caution at low-stress conditions. Through this work, we showed that by integrating the radial stress field theory with a simple flow-through-orifice experiment, intrinsic powder flow properties under low stresses could be reliably determined.

Tablet sticking occurrence is a persistent, costly, and time-consuming problem that needs to be resolved. Predicting the sticking tendency of a new formulation has been very difficult during the development batches because of short runs and limited data. A model formulation comprising ketoprofen and microcrystalline cellulose was used to predict the effect of magnesium stearate and sodium stearyl fumarate on the occurrence of tablet sticking relative to different punch metals. Lubricant amounts were varied from 0.0% to 2.0 %w/w. Five different metal coupons were used to represent punch metals. The sticking index (SI) of each formulation relative to each metal coupon was determined by measuring angle of internal friction and angle of wall friction by performing shear cell test and wall friction test, respectively. The SI was used to predict each formulation's sticking tendency rank order relative to metal coupon. Both lubricants show a decrease in the powder blend's sticking propensity with increased lubricant concentration. The predicted sticking propensity rank order was then validated by the compression study. The result suggests that the SI can be used to predict tablet sticking, such as by changing the composition of the formulation or changing the punch metal during tablet compression.

Purpose The shear cell test has been widely used to characterize flow properties of powders and granular materials. The purpose of this study is to address the gap between the extensive usage of the test and the limited methods available to analyze the data, and to introduce methodologies for comparing results for different initial consolidation stresses, materials, and testing devices. Method A library of shear cell data was established. Forty-one powders were included, and each material was tested under four different initial consolidation stresses. For each initial consolidation stress, 3 sampling replicates were performed. Results A dimensionless cohesion, C*, was defined as the cohesion divided by the initial consolidation stress. By identifying a correlation between the flow function coefficient (ffc) and C*, the effects of the initial consolidation stress and the testing device were separated. In addition, by identifying a mathematical correlation between the unconfined yield strength and the cohesion, the yield loci from different initial consolidation stresses could be collapsed into a single material characteristic line, enabling one to characterize each material by a single number (the characteristic slope). This approach can be used to economically compare different materials, or different testing devices. Conclusion The proposed method augments shear cell data analysis and significantly reduces the complexity of the shear cell data.

Flowability is a key consideration during the formulation and process development of oral solid dosage forms as it can have a critical impact on product quality. With a limited number of examples available in the literature, there is a need to better understand and share the typical flow properties of pharmaceutical materials. Here, historical data (3909 experiments) from a shear cell apparatus were extracted and analysed. These data were composed of different material types, including APIs, excipients, blends and granules from nearly a decade of development projects. APIs were found to have poor flow properties (ffc

The flow properties of five samples of a ceramic powder, characterized by different particle size distributions were measured at ambient temperature and at 500 °C with the High Temperature Annular Shear Cell. A significant increase of powder cohesion was observed at high temperature. A model combining a continuum approach and a particle–particle interaction description was used to correlate the powder tensile strength with the interparticle forces. The dependence of the tensile strength on powder consolidation and temperature is correctly described by the model.

Poor powder flow leads to many problems during manufacturing and can lead to inaccurate dosing and off-specification products. Powder flowability is commonly assessed under relatively high applied loads using shear cells by characterising the unconfined yield strength at a range of applied loads. For applied stresses below 1 kPa, it becomes increasingly difficult to obtain reliable values of the unconfined yield strength. The bulk cohesion and tensile strength of the powder are then obtained by extrapolating the yield locus to zero and negative loads, respectively. However, the reliability of this approximation for a given material is not known. To overcome this limitation, techniques such as the Raining Bed Method, Sevilla Powder Tester and the newly-developed Ball Indentation Method may be used. In this paper, we report our measurement results of the tensile strength of glass beads, α-lactose monohydrate and various sizes of fluid catalytic cracking powders determined by the Sevilla Powder Tester and Raining Bed Method and compare them with those inferred from the Schulze Shear Cell. The results of the latter are also compared with those of the Ball Indentation Method. The outcome suggests that in the case of shear cell tests, the extrapolation of the yield locus to lower or negative loads is unsafe. The ball indentation method enables the characterisation of highly cohesive powders at very low compressive loads; however extrapolation to negative loads is still not reliable. In contrast, the Sevilla Powder Tester and Raining Bed Methods are able to characterise the tensile strength directly, but high bulk cohesion poses difficulties as the internal bed failure needs to be analysed in order to reliably estimate the tensile strength. These methods provide a better understanding of powder flow behaviour at low stresses, thus enabling a greater control of manufacturing processes.

Developed to aid in the design of hoppers and silos, the shear cell is now frequently used to rank the flowability of powders relative to one another. While standards, such as ASTM D6773 and D6128, exist for shear cell tests, there are still differences between commercially available shear cell testers, such as cell geometry and size. In this work, we used two materials, a free-flowing alumina and a cohesive alumina, to compare measurements from three commercially available rotational shear cells. Results were collected and compared for cohesion, unconfined yield stress, major principal stress, pre-shear stress, flow function coefficient, bulk density, effective angle of internal friction, and the angle of internal friction. ANOVA methods were used to determine the statistical significance and relative size of each of these effects. This work has found that while, as expected, the material type has the largest effect on the shear cell results, the consolidation at which the material was tested and the tester type are also statistically significant effects. These results indicate that care should be taken when comparing the results between different shear cells.

A new design of an automated shear cell with diamond anvils for X-ray in situ studies has been developed and manufactured. As compared with a previous design, the dimensions and weight of the new cell have been reduced almost by one half on retention of the pressure range up to 100 GPa. To demonstrate the efficiency of the apparatus, the investigations of the possibility to use polycrystalline NaCl as a sensor of pressure at diffraction studies of samples in nonhydrostatic compression conditions have been carried out.

Shear testing provides rigorous estimates of flow properties relevant to the characterization, handling, and processing of powders, and is a necessary test procedure in the formal design of powder storage facilities. However, despite the automation of modern test equipment, it can be time consuming and expensive. In contrast, measurement of bulk density is straightforward and less laborious, and tapping devices are cheaper. Here we explore the relationship between Hausner ratio and cohesion and also examine correlation between Hausner ratio, σ c / σ y , and σ pre for a suite of 13 milled and 2 spray-dried lactose powders, 3 sand samples and 3 samples of refractory dust; Hausner ratio is the ratio of tapped bulk density to loose bulk density, σ c is major consolidation stress, σ y is unconfined yield stress and σ pre is preconsolidation stress. Cohesion and flow function were measured with an annular shear cell at values of σ pre up to 5 kPa. Loose poured bulk density was measured following a modified New Zealand standard and tapped density measurement was based on a method for dry dairy products and the European Pharmacopoeia; Hausner ratio at 1250 taps was used. Our results show that cohesion at σ pre of 0.31 kPa, 0.61 kPa, 1.20 kPa, 2.41 kPa, and 4.85 kPa correlates linearly with Hausner ratio; the slope and intercept of the correlation are functions of σ pre . A plot of σ c / σ y against Hausner ratio shows an exponential decay trend and regression yields two fitting parameters that correlate well with σ pre . These correlations are potentially useful for assessing flow characteristics when shear testing cannot be performed.

In this study, we used a two-dimensional annular shear cell to systematically investigate the dynamic properties of granular flow when it is subjected to varying bottom wall friction coefficients. A particle tracking method and image processing technology were employed to measure tangential velocity, slip velocity, local solid fraction, and granular temperature. The results demonstrated that the bottom wall friction coefficient played a crucial role in determining the dynamic properties of sheared granular flows, indicating that slip velocity is larger when a rougher bottom wall is applied. The results also indicated that the tangential velocity and granular temperature were reduced when the roughness of the bottom wall increased because of the strong frictional effect, which caused a larger dissipation of energy. The average granular temperature increased linearly when the solid fraction at each specific bottom wall friction coefficient increased.

This article addresses the subject of continuum modeling of dense granular flows with an application in high shear granulation. The possible use of continuum models and their ability to reproduce correct dynamics of such flows has been a subject of debate for a long time in the literature, and no consensus has been achieved so far. In this paper, we examine and compare two ways for making it possible to study dense granular flows in a continuum framework: the one that considers the stress tensor of a particulate phase as a sum of frictional and kinetic-collisional terms and the one that is based on modification of transport coefficients of the kinetic theory of granular flow. The latter framework is based on an analogy with molecular systems and how they behave at the phase transition from a liquid to a crystalline state. We show here that the formulation proposed in this work is able to correctly capture the phase transition and coexistence of solid-like and fluid-like phases in dense granular flows. This is in contrast to the model with added friction where the stress-strain dependence is shown to give a qualitatively different behavior compared to experimental data.

The firmness of whole beans and of separated embryos and testas from 20 soybean cultivars grown in the same field conditions was estimated after 40 min cooking with AACC International Approved Method 56-36.01. There were considerable variations in the firmness of whole beans, embryos, and testas among cultivars. Testas were much firmer than embryos because of their leathery texture and resistance at slots in the shear cell during compression. For soft cultivars, the firmness after 10 min cooking was also measured, and an apparent first-order reaction kinetics model was applied to estimate the initial firmness at 0 min cooking and the softening rate constant from firmness data after 10 and 40 min cooking. The estimated initial firmness at 0 min cooking and softening rate constant of embryos and testas varied widely among seven cultivars, and these two parameters were considered to be controlled by different genetic mechanisms, because no correlation was found between the parameters. The softening ...

In this short communication we explain and demonstrate why extreme caution has to be taken when applying conventional kinetic-frictional closures to continuum modeling of high shear granulation (HSG). By conventional models, we refer to closure laws where the kinetic and frictional stresses are summed up in order to get the total stress field. In a simple dense sheared system of a Couette shear cell, we study how the lack of scale separation affects the model predictions, both quantitatively and qualitatively. We show here that the spatial resolution has a significant effect on the magnitude of the kinetic and frictional contributions to the solid phase stresses. With this new investigation and previous studies of HSG it is concluded that conventional kinetic-frictional models are inadequate for continuum modeling of HSG.

Glass beads of varying diameters ( d = 2 , 3 , 4 , and 5 mm) are used to measure the ratio of shear-to-normal stress, or bulk friction coefficient, generated inside an annular shear cell at high shearing rates. The effects of the particle size, the solids concentration, and the shear rate are explored. It is found that (1) for a given particle size, the magnitude of the bulk friction coefficient decreases with increasing solids concentration, (2) for a given solids concentration, the bulk friction coefficient decreases with increasing particle size, and (3) the bulk friction coefficient is independent of the shear rate except for cases with low solids concentration, where it decreases with increasing shear rate. The boundary geometry is found to affect bulk friction only for dilute (low solids concentration) flows involving small particles.

A novel, green, and continuous method for solid-state polymorphic transformation of artemisinin by high temperature extrusion has recently been demonstrated. This communication describes attempts to understand the mechanisms causing phase transformation during the extrusion process. Polymorphic transformation was investigated using hot stage microscopy and a model shear cell. At high temperature, phase transformation from orthorhombic to the triclinic crystals was observed through a vapor phase. Under mechanical stress, the crystalline structure was disrupted continuously, exposing new surfaces and accelerating the transformation process.

Characterization of powder consolidation and flow is important to a large number of industries that process solids. A variety of powder testers exist today, however most are application specific and results they provide are mainly qualitative. Comparison studies have been attempted previously; their main focus was whether various methods correlate, while the reasons for disagreement in the results have seldom been investigated. Among the different methods used to characterize powder flow behavior, density-based methods are some of the simplest and most popular. They are also some of the least sensitive and least reproducible. A method comparison study was performed to characterize the variability in bulk density as measured by various powder flow characterization methods. It was found that the density of the powders tested in most unconsolidated methods had a near-perfect linear correlation with one another, suggesting that there exists a critical “dilated” density value that is independent of the measurement method and can be considered a material property. The densities of the powders in consolidated states correlated poorly, especially for the methods where consolidation mechanisms were not tightly controlled (i.e. tapping). In addition, the effect of the consolidation state of the powder bed during testing on cohesion measurements was studied. The cohesion measured by shear cells at differing consolidation states and by an avalanching method, during which the powder bed is dilated, were compared. It was found that the differences in cohesion results from the shear cells tested can be attributed to differences in the powder consolidation state. Cohesion results acquired from a dilated powder bed correlate more linearly with the shear cell cohesion results at low consolidation stresses than at high consolidation stresses; further supporting the impact of the powder bed packing state on the measurement of cohesion.

Powder flow of mixtures is complex and not properly understood. The selection of drug-excipient blends with inadequate powder flow can lead to quality issues of the final dosage form. Therefore, this work aims at a better understanding of how changes in powder flow of binary blends can lead to weight variability in pharmaceutical capsule filling. We used image-analysis-based powder avalanching and shear cell testing to study blends of paracetamol and microcrystalline cellulose. A pilot-scale machine with dosator principle was employed for encapsulation. As a result, the powder flow properties improved generally with rising amounts of microcrystalline cellulose. However, a negative correlation was observed between avalanche angle and angle of internal friction. Results were discussed and percolation theory was considered to explain abrupt changes in the observed flow properties. This was particularly helpful for analysis of the capsule-filling data, since capsule weight variability displayed a threshold behavior as a function of the mixture fraction. The capsule weight variability correlated with the angle of internal friction as well as with the angle and the energy of avalanches. Based on the results we proposed a strategy of how to design minimal weight variability into powder-filled capsules.

Animal feed often consists of different components and is normally stored in tower silos as a mixture. The components differ in terms of their flow properties, which determine the flow out process. In this study a series of key components like crushed grain and crushed meals of native and imported oils and legumes were examined. To characterize the flow properties, shear strength measurements with the Jenike shear cell were carried out and the flowability ffc and the outlet diameter were calculated. The tensile strength was measured with a device according to Ashton. The results show the known tendency between the flowability ffc and the amount of fine components. Because of the different bulk materials the coefficient of determination is low. The flowability based on own investigations is lower than the flowability of Jenike. The evaluation of the results did not demonstrate any influence of the ingredients on the flow properties of the components examined.