A new method for evaluating powder flowability using constant-volume shear tester,

This is an article translated from the original version published in the Journal of the Society of Powder Technology, Japan. A new method for evaluating powder flowability is developed using a constant-volume shear tester; this tester measures the upper and lower normal stresses and the shear stress acting on a powder bed. A single shear test provides a series of characteristics, such as the powder yield locus (PYL), consolidation yield locus (CYL), critical state line (CSL), shear cohesion, stress relaxation ratio, stress transmission ratio, and void fraction. The values of shear stress as a function of the normal stress and void fraction are visualized in three-dimensional diagrams. Furthermore, powder flowability is evaluated using a flow function obtained from the PYL.     

Predicting the flowability of alumina powder during batch grinding through the establishment of a grinding kinetic model

Grinding is one of the main unit operation in industrial processes handling powders. The particle size reduction that takes place during grinding tests, usually results in a significant change in the flow behavior of the ground powder. Up to now, a model predicting the evolution of powder flowability with grinding time, according to the operating conditions is still missing. In this paper, a methodology combining a grinding kinetic model and a flowability model involving the population-dependent granular Bond number is developed. The methodology has been applied to an alumina powder, ground in a batch ball mill. The flow function coefficient of the ground samples is measured after various grinding times in a powder shear tester. The comparison between model predictions and experimental data shows that this method allows an accurate prediction of the powder flow behavior over the first sixteen minutes of grinding.     

Investigation of flow properties of powders by means of a uniaxial tester, in relation to direct tablet compression

Unexpected poor flowability during commercial production of a direct compression tablet formulation initiated an investigation of the flow properties of the powder mixture and its components by means of a uniaxial tester. The failure function—a curve describing the strength of the powder bed as a function of the maximum main stress that has consolidated the bed—of the powder mixture and its components was determined. The drug was more cohesive than the filler, which was somewhat more cohesive than the powder mixture. Three excipients—a binder, a glidant and a lubricant—constituting 3.5 w/w% of the formulation improved the flowability of the mixture of active ingredient and filler. The failure function discriminated powder mixtures with poor flow from mixtures with medium or good flow. However, it was not possible to discriminate medium from good flow by means of the failure function. Attempts to correlate univariately the flow property parameters of the powder mixtures with particle size data or flow property data of included active ingredient and filler batches failed. Therefore a multivariate approach was tested. Principal component analysis (PCA) and projection to latent structures by means of partial least squares (PLS) were employed. An excellent PCA model was obtained with the flow properties of the powder mixture. A good PCA model of tableting performance—based on tablet weight variation and tablet machine speed—was obtained.     

Simultaneous Deposition of Powder in Three Parallel-Oriented Cylindrical Dies

The inhomogeneity of bulk density distribution created during the die filling process might cause quality problems for powder compacts, such as distortion, lamination, and cracking. To avoid these problems, understanding the die filling process and ensuring a uniform pre-compaction powder deposition are necessary. The second-generation pressure deposition tester (PDT-II) was developed to investigate simultaneous deposition of powder into multiple dies. Its design requirements and new features were proposed through evaluating the main strength and limitations of the mass deposition tester (MDT). The operation of the PDT-II and analysis of its data showed that it generates real-time deposition profiles of the entire process for multiple locations. PDT-II data can be used to study the effects of various filling-related parameters (such as die shape, powder flowability, and feed shoe speed) on the deposition process and final pressure distribution. For cylindrical dies filled with a granulated powder with d₅₀ = 600 μm (1) at low feed shoe speeds (20 and 100 mm/s), the half circle close to the leeward end had higher final pressure values than the forward half circle; (2) at high feed shoe speed (500 mm/s), the final pressure distribution was more uniform than at lower feed shoe speed; (3) the final within-die pressure distribution at the bottom of the dies was not always symmetrical about the center line of the feed shoe movement direction, even though sometimes it was quite symmetrical; (4) the overall trend was that pressure decreases with increasing radial distance for lower feed shoe speeds; and (5) higher feed shoe speed (500 mm/s) resulted in higher final pressure values (774.5 to 1424.5 Pa) than lower feed shoe speeds (20 and 100 mm/s) (235.2 to 1136.0 Pa) at most of the locations. The results proved that feed shoe speed does have an effect on pressure distribution and its uniformity.     

Powder deposition in three parallel-oriented dies of cylindrical and E shapes

The second generation pressure deposition tester (PDT-II) was used to evaluate the die filling process in multiple dies. Three parallel-oriented dies of cylinder and E-shape were filled with an alumina powder at different feed shoe speeds. The results indicated that for cylindrical dies at lower feed shoe speed, the center area had the highest pressures; at higher speed, pressure distribution was irregular, complicated, and varied more. One reason for this was relatively low bulk density and small particle size of the powder, which led to relatively poor flowability. For E-shaped dies, due to wider opening of the middle leg, its pressures were higher than those of the other legs. Compared to another powder (BPM) with denser, bigger, and less spherical particles, the alumina powder had the highest final pressures closer to the middle leg, instead of being closer to the back as for the BPM. This was basically due to its physical properties (such as particle size and shape). This research demonstrated that powder physical properties, such as particle size and shape, had pronounced effect on powder deposition. Also, die shape complexity could affect the pattern of powder flow and deposition.     

Rate-Dependent Elasto-Viscoplastic Constitutive Model for Industrial Powders. Part 1: Parameter Quantification

ABSTRACT

The rate-dependent mechanical behavior of a dry industrial powder (MZF powder) was studied using a cubical triaxial tester (CTT) within the context of a new elasto-viscoplastic model (PSU-EVP model). The compression and shear properties of the powder were quantified at compression rates of 0.62, 6.21, and 20.7 MPa/minute with pressures up to 11 MPa. Test results demonstrated that the compression and shear responses of the powder were nonlinear, consistent, and reproducible (coefficient of variation or COV ≤ 15%). Also, MZF powder exhibited varying elastic and plastic deformation at different pressure levels that were quantified using statistical correlations (R² > 0.90). For example, the average bulk modulus and shear modulus values for MZF powder increased linearly with pressure (R² > 0.90) at all compression rates. The failure stress values also increased with the increase in mean pressure. For instance, at a compression rate of 0.62 MPa/minute, failure stress increased from 5.0 to 13.3 MPa as the confining pressure increased from 2.2 to 8.5 MPa. Similar effects were noted at compression rates of 6.21 and 20.7 MPa/minute. Overall, failure stress decreased with increasing compression rate. From the data collected, it was demonstrated that compression rate does have substantial effect on the compressibility and shear behavior of powders that can be quantified using the CTT and is suitable for use in the PSU-EVP model.     

小麦种类及加工方式对全麦粉粉体特性的影响

为了研究全麦粉粉体特性,以卡尔指数原理为理论基础,使用粉体综合特性测试仪,对红麦、白麦、加麦3种不同种类的小麦面粉及不同加工方式下全麦粉粉体的特性,包括Carr流动性综合指数Fw和喷流性综合指数Fd,及其单项检测项目等进行逐一对比分析。结果表明,不同种类小麦的面粉及全麦粉的流动性呈显著性差异,面粉与全麦粉流动性呈极显著的差异性(p<0.01),但不同加工方式的全麦粉流动性没有显著性差异;面粉及全麦粉的流动性状均表现不太好,面粉有相当强的喷流性,但全麦粉仅表现出有倾向的喷流性状。     

Experimental investigation on the flowability properties of cohesive carbonaceous powders

The flowability properties of two carbonaceous powers (anthracite coal and petroleum coke), including angle of repose (AOR), Hausner ratio (HR) and powder compressibility (C), etc., were determined. The effects of particle size, external moisture content (MC) and power type on powder flowability properties were investigated. The results indicate that as the powder particle size increases, the AOR, HR and C decrease, respectively, and the powder flowability becomes better. As the powder external MC increases, the AOR, HR and C increase, respectively, and the powder flowability becomes worse. The anthracite coal has lower values of AOR, HR and C, and higher values of flow function (FF) than those values of petroleum coke. Therefore, anthracite coal has better flowability compared to petroleum coke. Meanwhile, there exists a good linear correlation between AOR and HR.     

粉粒体三次物性的分析与测量

综述了粉粒体几种主要三次物性的分析测量方法 ,包括粉粒体流动性、流化特性、喷流性和流变性 ,总结了这些测量方法的共同特点 ,并对粉粒体基础研究发展前景做了分析。     

Effect of matrix composition on the flowability of spray-dried detergent powders

The flowability of spray-dried laundry detergent is important for manufacturing process performance and reliability, and product quality; it is strongly dependent on formulation. In this work, a detailed study of four model formulations provides fundamental understanding of the role of particle composition, and micro-structure, on spray-dried detergent powder flow behaviour. All spray-dried powders studied contained the sodium salt of linear alkylbenzene sulphonate (NaLAS) and sodium sulphate. However, their formulation varied depending on either the initial water content (30.0 or 63.0 wt%) of the slurry or the addition of sodium silicate with molar-ratios of 1.6 and 2.35 SiO₂:Na₂O. The nil-silicate powder, made from low water content slurry, had the poorest flow characteristics. The addition of the silicate binder, significantly improved flowability, 2.35 ratio silicate, providing better flowability than 1.6 ratio. Remarkably, increasing the water content of the slurry also improved flowability significantly. Detail analysis showed that this was due to changes in composition and micro-structure of the composite matrix formed on drying the liquid components of the slurry, and that the improved flowability was due to improvements in mechanical strength of this matrix. These changes in mechanical robustness were significantly more important to the flowability than the powder shape.     

Evaluation of mechanical properties of nanoparticles using a constant-volume shear tester

Nanoparticles have advantageous small-size and surface effects that impart them with unique mechanical properties. To evaluate these properties, a constant-volume shear tester that can precisely measure stresses on the shear plane was used. Six samples, namely, hydrophilic and hydrophobic silica, alumina, and titania nanoparticles, were prepared for the shear tests. For each sample, a single shear test provided the void fraction, stress relaxation ratio, stress transmission ratio, powder yield locus, consolidation yield locus, critical state line, shear cohesion, and flow function. All the tests were conducted under ambient conditions using powder beds, in which the void fractions were in the range of 0.89–0.96. A series of analyses demonstrated that the hydrophilic nanoparticles have lower flowability than the hydrophobic nanoparticles, indicating that moisture on the surface increases the cohesion and inhibits the flow.     

Effect of some commercial grades of microcrystalline cellulose on flowability, compressibility, and dissolution profile of piroxicam liquisolid compacts

The technique of liquisolid compacts is a promising method toward enhancing the dissolution of poorly soluble drugs. Lower flowability and compressibility is one of the limitations of this technique. The evaluation of effects of different grades of microcrystalline cellulose (MCC) on flowability, compressibility, and dissolution of liquisolid systems were the aims of this study. For this means, several formulations were prepared using various grades of MCC as carrier. Propylene glycol (PG), silica, and sodium starch glycolate were used as nonvolatile solvent, coating material, and disintegrant, respectively. Then flowability, friability hardness, and dissolution rate of prepared formulations were studied. The effect of tablet aging on mentioned properties was also investigated. The results showed that among the evaluated different grades of MCC, compacts containing MCC PH 101 and 102 showed better dissolution profiles. Harder compacts were obtained using MCC PH 101 and 200 as carriers. Better flowability was observed in compacts containing MCC PH 101. Also, these compacts demonstrated acceptable friability. Aging had no effect on hardness and dissolution profile of liquisolid tablets. It could be concluded that MCC PH 101 is a suitable carrier for preparing liquisolid systems for having acceptable flowability, friability, hardness, and dissolution profile.     

Influence of Crystal Properties on Powder Flow Behavior of an Aromatic Amine and L-Glutamic Acid

Polycrystalline particles with a roughly spherical shape (spherulites) have been identified in the industrial production of an aromatic amine derivative, where powder handling is one of the downstream processes following crystallization. This comparative study focuses on how uniaxial flow functions as measures of flowability of dry material of L-glutamic acid and an aromatic amine are affected by the crystal morphology and size, as analyzed by the chord length distribution measurements (FBRM) and scanning electron microscopy (SEM). L-glutamic acid was chosen as a model substance since it can be crystallized as spherulites as well as needle-shaped and polyhedral particles. Failure strength values were measured as a function of consolidation stress using the uniaxial tester. The failure strength values of L-glutamic acid were found to be lower for polyhedral particles than for needle-shaped particles with approximately the same mean chord length. Needle-shaped particles were found to have lower values for failure strength than L-glutamic acid spherulites with smaller chord lengths. It has been shown that spherulites are more unstable with respect to particle breakage than the other morphologies. Although the chord length distributions of the L-glutamic acid spherulites were shifted towards smaller values than those of the aromatic amine spherulites, the failure strength of the aromatic amine particles is more than four times as large. This can be explained by more extensive particle breakage during filtration, sample storage, and consolidation of the aromatic amine.     

添加润滑剂对烧结钕铁硼磁体性能的影响

研究了烧结钕铁硼永磁材料的粉末流动性及添加润滑剂对粉末流动性与磁体取向度和磁性能的影响.结果表明:影响松装状态磁粉流动性的主要因素是粉末颗粒团聚,影响密实磁粉流动性的主要因素是颗粒间的摩擦力.添加适量的润滑剂可以防止粉末颗粒团聚、明显地减小摩擦力,改善粉末流动性,提高磁体的取向度、剩磁与磁能积.采用添加润滑剂和橡皮模等静压制成型工艺,批量生产的烧结钕铁硼磁体性能达到:Br=1.457 T,jHc=1148 kA/m(14.43 kOe),(BH)max=408 kJ/m3(51.3 MGOe).     

Flowability of binary mixtures of commercial and reprocessed ibuprofen through high shear wet milling (HSWM) with lactose

This study investigates the flow properties of binary mixtures of both commercial ibuprofen and reprocessed ibuprofen through high shear milling with lactose powders. Ibuprofen is recrystallized in a 30% water–ethanol mixture before high shear wet milling (HSWM). In-situ Process Analytical Techniques (PAT) (Labmax®) is used to study the HSWM process dynamics, with particle size measured by a Lasentec Focused Beam Reflectance Measurement, FBRM®. The flow properties of the binary mixtures of the different ibuprofen particles and its binary mixtures with lactose were measured using a Schulze® RST-XS ring shear tester. Results show that the morphology of ibuprofen was changed from needle to hexagonal like crystals during recrystallization and crystal size was reduced dramatically by HSWM for 1 h. The flowability of milled ibuprofen powders is reduced significantly due to its reduced size and change of surface morphology. Mixing the HSWM ibuprofen powders with lactose enhanced its flow properties. However, the increase of the mixture flowability for HSWM ibuprofen is less significant in comparison to the binary mixtures of lactose with commercial ibuprofen.     

Impact of grinding aids on dry grinding performance,bulk properties and surface energy

In dry fine grinding processes the relevance of particle-particle interactions rises with increasing product fineness. These particle-particle interactions reduce the grinding efficiency and complicate the process control. The adsorption of grinding aid molecules on the product particle surface is a common measure to handle these effects. To ensure an efficient grinding aid application, the impacts of additives on particle and bulk properties, which influence the micro-processes inside the mill, need to be understood. Within this study the effects of several grinding aids on dry fine grinding of limestone in a laboratory vibration mill were investigated. Unlike in many other scientific works, the impacts of grinding aids were analyzed on different levels simultaneously: Grinding success and agglomerate size distributions were evaluated by wet and dry particle size measurements, respectively. Additionally, material coating on the grinding media, powder flowabilities and particle specific surface energies were measured. It was shown that all of the investigated grinding aids influence the grinding efficiency. However, the formation of agglomerates is not necessarily linked to the product fineness. Furthermore, a strong impact of certain grinding aids on the flowability of the product powder was determined. Thereby, the bulk flow behavior also determines the grinding result as it affects the stress mechanism inside the mill. Moreover, a direct relation between surface energy and powder flowability as well as agglomeration behavior could be demonstrated.     

卡尔指数法在评价煤粉粉体特性中的应用

以卡尔指数原理为理论基础 ,使用MT - 10 0 0型多功能粉体物性测定仪 ,成功测定了 3种煤粉材料的粉体流动特性和喷流性特性 ,并结合该测定结果 ,探讨了煤粉加工生产中的注意事项及具体应用     

Analysis of powder behaviour in bin blending processes at different scales using DEM

Obtaining a desired content uniformity with satisfactory flowability is one of the main challenges during blending process of the pre-mixture with lubricants. In this study, Discrete Element Method (DEM) simulations were implemented to examine blending time and mixing behaviour during the blending process on the lab and industrial scales. The main goal was to investigate the possible influence of operational conditions on the blending behaviour and the change in powder cohesivity during the scale-up process. The effects of rotational speed and filling mass on the particles' travelled distance, velocity, shear stress and blending time were studied in the simulations. Based on the simulations, blending time and particle exposure to shear during the blending process were calculated for different scales. It was observed that the system's mass significantly influences them, and the effect of rotational speed could be neglected. The novelty of this paper is connecting particle exposure to shear from DEM to the flow function coefficient (ffc) of powder from experiments. It was done to define a critical range of exposure to shear that changes the powder flowability in different scales.     

智能化铸造型砂多项力学性能测试仪及其应用

介绍一种新型的智能化铸造型砂多项力学性能测试仪，该测试仪采用先进的非电量电测技术与计算机技术相结合，单片机与串口微机联合测控，所测力学性能参数均是被测标准砂样受载变形特征曲线上的特征点或特征函数所对应的特征值，其物理意义准确、具体；介绍了型砂塑性变形临界值、回弹势能的概念及其测试方法；测试仪测值误差小，精度高，数据随即显示、微打和PC机存储三结合；操作简单，使用方便，市场广阔，应用前景可观。     

Powdered self-emulsified lipid formulations of meloxicam as solid dosage forms for oral administration

The objectives of this study were to prepare a powdered self-emulsified (SEDDS) formulation of meloxicam and to compare its oral bioavailability against commercial Mobic^® tablets. The SEDDS formulation was prepared by in situ salt formation of meloxicam in a blend of lipid excipients and aqueous tris (hydroxymethyl) aminomethane solution. The liquid SEDDS was subsequently adsorbed on silica powder and was tested for size, flow, and crystal growth. The flowability index of the powdered SEDDS was borderline acceptable. Absence of crystal growth with storage was confirmed by DSC and PXRD studies. Dissolution of meloxicam from the powdered SEDDS was >90% vs. <12% for powdered meloxicam and <80% for the commercial tablets. Stability of the powdered formulations after storage in gelatin and HPMC capsules was also evaluated to study the effect of water migration from the fill into capsule shells. Capsules softened to a different extent as a function of fill material with HPMC capsules showing greater resistance to water migration. Finally, oral bioavailability of the formulations was evaluated in beagle dogs. Powdered meloxicam SEDDS formulation showed a 1.3-fold increase in AUC vs. commercial Mobic^® tablets. Overall, this study described a novel SEDDS formulation of meloxicam and outlined a systematic approach to adsorbing and testing the flow and stability behavior of powdered SEDDS formulations.