Polydisperse powder mixtures: effect of particle size and shape on mixture stability

The effect of the shape and size of the components on the stability of mixtures was evaluated in binary mixtures of drug and carrier. Aspirin was used as model drug; spray-dried lactose and microcrystalline cellulose were used as carriers. The coefficient of variation (CV) of the drug in the mixture at various time intervals during mixing was used as a measure of homogeneity. The stability of mixtures was assessed under conditions that were conducive to segregation—in this case, prolonged mixing. The pattern of change in CV with time was analyzed in terms of convective, shear, and diffusive mixing stages. The variation resulting from a change in the shape of the carriers was smaller than that resulting from size differences. The segregation rate constant, calculated on the assumption of a first-order mixing process, was found to be larger in mixtures having components of different shape than in mixtures having components of similar shape. In mixtures of micronized drug and carrier, the pattern of change in the CV of drug with mixing time was attributed to the distribution of agglomerates of micronized drug during convective mixing, followed by shearing of agglomerates and, finally, the distribution of the primary particles during diffusive mixing. Mixtures of non-cohesive powders of similar size and shape behaved like random mixtures of non-interacting components.     

The Effect of Particle Morphology on the Physical Stability of Pharmaceutical Powder Mixtures: The Effect of Surface Roughness of the Carrier on the Stability of Ordered Mixtures

The effect of particle morphology of the components on the physical stability of ordered mixtures was determined for a model system comprised of a mixture of micronized aspirin and a monodisperse carrier. Spray-dried lactose, crystallized lactose, microcrystalline cellulose, and dextrate were used as carriers. The surface texture of the carriers was quantified in terms of the ratio of the perimeter of the particles to that of an idealized shape at a constant magnification. Mixtures containing highly textured carriers segregated to a lesser extent than those containing smoother textured carriers. This was postulated to be due to the presence of a higher concentration of surface asperities on the coarse carriers that can constitute potentially strong adhesion sites for the fine component because of their higher energy relative to adjacent areas on the surface. The effect of the addition of a ternary component, magnesium stearate, on the stability of the above mixtures was studied. The observed differences in the segregation response were attributed to electrostatic charge effects.     

Segregation Quantification of Two-Component Particulate Mixtures: Effect of Particle Size,Density, Shape,and Surface Texture

Segregation, which occurs during handling, processing, and storage of particulate material, is highly dependent on properties such as particle size, size distribution (for continuous mixtures) or size ratio (for binary mixtures), particle density, shape, and surface texture. Quantification of the relationship of material properties to segregation becomes an important link in understanding and controlling segregation. Due to lack of well-developed equipment in the market, quantification of segregation of multicomponent particulate mixtures is currently a challenge. In this study, the effects of particle size, density, shape, and surface texture of two-component particulate mixtures (glass beads and mash poultry feed) on segregation were quantified with the use of the second generation of primary segregation shear cell (PSSC-II) developed at Penn State. It was concluded that (1) irregularly shaped (nonspherical) coarse particles or higher porosity of coarse component of a binary mixture lead to higher segregation potential; (2) the higher the density and smoother the surface of the fine component of a binary mixture, the higher the segregation potential; and (3) the fine particle properties, to a certain extent, determine the particle size–related effects such as absolute size and size ratios, i.e., if fine particle properties of a binary mixture change, the size-related effect on segregation potential would definitely change.     

Segregation Quantification of Two-Component Particulate Mixtures: Effect of Particle Size, Density, Shape, and Surface Texture

Segregation, which occurs during handling, processing, and storage of particulate material, is highly dependent on properties such as particle size, size distribution (for continuous mixtures) or size ratio (for binary mixtures), particle density, shape, and surface texture. Quantification of the relationship of material properties to segregation becomes an important link in understanding and controlling segregation. Due to lack of well-developed equipment in the market, quantification of segregation of multicomponent particulate mixtures is currently a challenge. In this study, the effects of particle size, density, shape, and surface texture of two-component particulate mixtures (glass beads and mash poultry feed) on segregation were quantified with the use of the second generation of primary segregation shear cell (PSSC-II) developed at Penn State. It was concluded that (1) irregularly shaped (nonspherical) coarse particles or higher porosity of coarse component of a binary mixture lead to higher segregation potential; (2) the higher the density and smoother the surface of the fine component of a binary mixture, the higher the segregation potential; and (3) the fine particle properties, to a certain extent, determine the particle size-related effects such as absolute size and size ratios, i.e., if fine particle properties of a binary mixture change, the size-related effect on segregation potential would definitely change.     

Influence of Particle Size on the Distributions of Liposomes to Atherosclerotic Lesions in Mice

ABSTRACT

In order to confirm the efficacy of liposomes as a drug carrier for atherosclerotic therapy, the influence of particle size on the distribution of liposomes to atherosclerotic lesions in mice was investigated. In brief, liposomes of three different particle sizes (500, 200, and 70 nm) were prepared, and the uptake of liposomes by the macrophages and foam cells in vitro and the biodistributions of liposomes administered intravenously to atherogenic mice in vivo were examined. The uptake by the macrophages and foam cells increased with the increase in particle size. Although the elimination rate from the blood circulation and the hepatic and splenic distribution increased with the increase in particle size in atherogenic mice, the aortic distribution was independent of the particle size. The aortic distribution of 200 nm liposomes was the highest in comparison with the other sizes. Surprisingly, the aortic distribution of liposomes in vivo did not correspond with the uptake by macrophages and foam cells in vitro. These results suggest that there is an optimal size for the distribution of liposomes to atherosclerotic lesions.     

ZnO粉颗粒形状和大小对压敏陶瓷电阻的影响

对于多晶陶瓷烧结体，初始粉料的颗粒形状和大小会影响烧成多晶陶瓷的微观结构，进而影响到陶瓷性能。本文研究了不同颗粒形状和大小的ＺｎＯ粉料对压敏电阻性能的影响。结果表明，颗粒细的球状ＺｎＯ粉有利于获得微观结构均匀的压敏电阻，有助于提高通流能力。     

Dissolution Characteristics of Interactive Powder Mixtures. Part One: Effect of Solubility and Particle Size of Excipients

Abstract

Interactive mixtures of fine cohesive drug powders and coarse free flowing excipients are reported to increase dissolution rates of poorly soluble drugs. However, dissolution rates are known to be affected by the solubility characteristics of the excipients as well as excipients surface characteristics after mixing with lubricant.

In this study the effects of solubility and particle size of excipients on dissolution of micronized griseofulvin from interactive powder mixtures were investigated. Quantitative assessment of dissolution from such mixtures showed that systems containing soluble excipients increased dissolution of the drug more efficiently than mixtures prepared using insoluble excipients. The role of the soluble excipient was more significant after mixing with magnesium stearate. Excipients of smaller particle sizes increased dissolution more efficiently than their large size counterparts. Effects of particle size were particularly significant in case of water insoluble excipients.     

Effect of Training on Two-way Shape Memory Effect and Its Stability in a Ti-Ni-Hf High Temperature Shape Memory Alloy

The Effect of the thermal cycling training under constant strain on the two-way shape memory effect (TWSME) in a Ti36Ni49Hfl5 high temperature shape memory alloy (SMA) has been investigated by bending tests. The results indicated that the training procedure is beneficial to get the better TWSME. The two-way shape memory strain increases with increasing the training strain. And it decreases with increasing the training temperature. The TWSME obtained in the present alloy shows poorer stability compared with that obtained in the TiNi alloys.     

铝粉粒径对销毁某未爆弹药影响的试验研究

为提高某种新型未爆弹销毁方式的工作效能和操作安全性,基于销毁装置内复合高热剂自蔓延燃烧过程,利用试验分析研究了铝粉粒径大小对销毁该种未爆弹药的影响。结果表明:74~178μm范围内,铝粉粒径越大,金属熔流出口速度达到的峰值越低;同时,铝粉粒径过小(≤89μm),会导致销毁装置内复合高热剂反应过于激烈,容易出现燃爆现象;而124~178μm粒径范围的铝粉适用于榴弹弹丸、破甲弹战斗部、手榴弹、地雷等多种壳体厚度不超过9 mm的猛炸药弹丸的未爆弹销毁工作。为以后提高未爆弹销毁工作效能、保护销毁人员安全提供参考。     

形状记忆合金超弹性阻尼特性及工程应用

从工程中一种常见机器隔振模型出发,推导出了系统传递功率流表达式.计算模拟形状记忆合金的超弹性循环曲线并计算了TiNi形状记忆合金丝加卸载循环时的超弹性等效阻尼,并据此将合金丝作为一种等效阻尼材料应用到隔振模型中.通过计算机仿真,得出在此模型中使用记忆合金丝作为阻尼材料时不同的环境温度和系统振幅对模型隔振效果的影响.     

硅灰石形貌和尺寸因素对PTFE复合材料摩擦学性能的影响

利用同种材质的硅灰石填料有着不同的形貌(纤维状和粒状)和尺寸(d=10μm～60μm;l=50μm～600μm)的特征,考察了填料的形貌和尺寸因素对聚四氟乙烯(PTFE)复合材料磨损性能的影响,并探讨了其影响机理。研究发现,在低载荷下,对于同样尺寸的填料,粒状填料比纤维状填料填充的PTFE复合材料有着更好的耐磨性;而对于纤维状填料,小尺寸填料填充的PTFE复合材料有着更加优越的耐磨性能。在高载荷下,情况则完全相反,此时大尺寸及纤维状填料填充的PTFE复合材料的耐磨性能更加优越。     

Influence of the Size of Micronized Active Pharmaceutical Ingredient on the Aerodynamic Particle Size and Stability of a Metered Dose Inhaler

Pharmaceutical inhalers are often used to treat pulmonary diseases. Only active pharmaceutical ingredient (API) particles from these inhalers that are less than approximately 5 µm are likely to reach the lung and be efficacious. This study was designed to investigate the impact of micronized API particle size on the aerodynamic particle size distribution (PSD) profile and the particle size stability of a suspension metered dose inhaler (MDI) containing propellant HFA‐227 (1,1,1,2,3,3,3 heptafluoropropane) and a corticosteroid. The median API particle size ranged from 1.1 µm to 1.8 µm (97% to 70% of particles <?3 µm, respectively). This study showed that increasing the particle size of the API used to manufacture a suspension MDI product increased the aerodynamic PSD of the MDI product. Furthermore, upon storage of the MDI product under temperature cycling conditions, samples containing larger‐size API particles were less stable with respect to their aerodynamic PSD than those with smaller‐size API particles. It was found that size‐dependent particle growth and/or aggregation of the suspended API may be occurring as a result of temperature cycling. In conclusion, this study has shown that the particle size of the raw API impacts the properties and stability of the emitted aerosol spray. Based on the findings from this study, it is recommended that the API particle size be carefully controlled in order to meet specifications set for the finished MDI product.     

Measurement of Bulk Mechanical Properties and Modeling the Load-Response of Rootzone Sands. Part 2: Effect of Moisture on Continuous Sand Mixtures

The compression and failure responses of four rootzone sand mixtures (with different types of particle shapes) were analyzed, compared, and modeled at two different moisture states (air dried and 30 cm tension). Differences in particle packing characteristics arising from particle shape and moisture were quantified. The air-dried and moist samples of the sand mixtures had initial bulk density (IBD) values ranging from 1.55 to 1.67g/cc and 1.23 to 1.48g/cc, respectively. The low IBD values observed for moist mixtures were attributed to the particle-particle agglomeration effects that take place in the presence of moisture. In addition, it was observed that the sand mixture's porosity increased with decreasing particle sphericity. During compression testing, moist samples underwent a greater volumetric deformation compared to the air-dried samples for the same pressure levels, e.g., at 69kPa, the volumetric strain of moist round sand mixtures was 8% higher than that of the air-dried round sand mixtures. Therefore, moisture acted as lubricant during volumetric compression of sand mixtures. Also, the bulk modulus values decreased with increasing moisture content and decreasing particle sphericity. During shear testing, the moist samples underwent a larger amount of strain deformation compared to the air-dried samples for the same stress difference values. This suggests that the presence of moisture makes the sand mixtures ductile during shear testing, unlike the usual brittle response in air-dried state. Shear modulus values linearly increased with the increase in mean pressure for the air-dried samples, whereas, for moist samples, the shear modulus values increased gradually or remained practically constant. The effect of pressure, moisture, and particle shape was also quantified for two elastoplastic parameters (consolidation and swelling indices). It was generally observed that the average consolidation index values decreased with pressure but increased with moisture and particle angularity. On the other hand, average swelling index values increased with pressure, moisture, and particle angularity. Overall, it was concluded that the moisture and particle shape had a decisive influence on the compression and shear profiles of continuous rootzone sand mixtures.     

Tableting of Eudragit RS and Propranolol Hydrochloride Solid Dispersion: Effect of Particle Size,Compaction Force,and Plasticizer Addition on Drug Release

The application of a solid dispersion (SD) system of propranolol HCl and Eudragit RS was evaluated in the preparation of prolonged release tablets. The effects of SD size fraction, compaction force, and inclusion of plasticizers [namely diethylphtalate (DEP) and triethylcitrate (TEC)] on crushing strengths of matrices and release profile of drug were also investigated. The results showed that when compressed as a tablet, the SD system was more efficient in prolonging drug release than physical mixture. This effect was due to formation of much harder tablets of the SD system (crushing strength 8.5 kg) compared with those of physical mixtures (crushing strength 2.7 kg). All matrices of the SD system showed release rate patterns that were best described by the Higuchi equation. It was also shown that the rate of drug release decreased from 19.8% to 9.13% min^??1/2 as the SD size fraction decreased from 300–350 to 125–250 µm. However, further reduction of size fraction did not significantly affect tablet crushing strength and drug release rate. Increase in compaction force from 5 to 30 kN increased the crushing strength of matrices from 2.9 to 13.6 kg. However, the rate of drug release remained nearly unchanged beyond compaction pressure of 10 kN, indicating that crushing strength of matrices in the range of 8.5–13.6 kg did not affect drug release rate. The addition of 5% or 10% of either plasticizer (DEP or TEC) led to an increase in crushing strength of matrices and more retardation of drug release. This effect was more pronounced for higher concentrations of plasticizers. This effect was probably due to more plastic deformation of matrices under the compaction force, which helped matrices to retain their shape throughout the dissolution test.     

反应条件对CoFe2O4颗粒形貌、粒径大小和磁性的影响

以FeSO4（NH4）2SO4、6H2O、CoCl2·6H2O、C6H5Na3O7·2H2O为前驱物,采用水热法合成了钴铁氧体CoFe2O4。用XRD、TEM、VSM分别测试了CoFe2O4颗粒大小、形貌、饱和磁化强度和矫顽力,探讨了反应时间、温度、溶质浓度、酸碱环境对颗粒粒径大小、形貌及其磁性能的影响。结果表明,适度的减短反应时间、降低温度、选取合适的溶质浓度和NaOH溶液浓度,可以得到粒径小、形貌统一的纳米颗粒,并且有助于增大CoFe2O4颗粒的饱和磁化强度。     

Al2O3粉粒度对硅溶胶涂料及陶瓷型壳性能的影响

采用三种不同粒度的Al2O3粉配制涂料,研究涂料的流变性能,型壳力学性能及其高温自重变形性,并通过对实际浇注情况验证三种Al2O3粉的优劣.实验结果表明,三种粉料配制的涂料均具有良好的流变性能,W20+W40Al2O3粉做面层涂料工艺性能良好,型壳1500℃高温抗弯强度可达1.14MPa,自重变形减小到2.98%,可以满足合金浇注要求.实际浇注的铸件表面光滑,无粘砂、劈缝等缺陷.     

喷印工艺控制参数对水性油墨墨滴形态的影响

目的为了提高水性油墨的喷墨印刷质量,通过控制喷印工艺参数以获得良好的墨滴形态。方法分析喷印工艺控制的关键参数以及墨滴形态的表征参数,通过单因素工艺参数对墨滴形态影响的实验,分析电压、点火频率和脉冲宽度对墨滴形态各评价指标的影响程度,并运用AHP法构建墨滴形态的质量分析模型;通过多因素工艺参数组合对墨滴形态影响的正交实验,分析各工艺参数与墨滴形态参数之间的关联性,并结合质量评价模型综合评判喷印工艺参数对墨滴形态的影响。结果喷印工艺参数电压、点火频率和脉冲宽度共同影响墨滴形态的质量,脉冲宽度对其影响最大,点火频率次之,电压的影响程度最小,其权重分别为0.462,0.272,0.266。结论水性油墨喷印工艺中,通过合理地控制喷印工艺的关键参数,可以有效地提高墨滴形态质量,从而获得良好的印刷品质量。     

滑石粉粒径对PVC/滑石粉复合材料力学性能和热膨胀系数的影响

使用钛酸酯偶联剂对不同粒径的滑石粉改性,并通过熔融共混方法制备了PVC/滑石粉复合材料。通过力学性能测试、线性膨胀测试等方法研究了滑石粉粒径对复合物的形态结构、力学性能和线性膨胀系数的影响。实验结果表明,在实验范围内随着滑石粉含量的增加,400 mesh滑石粉会使复合体系拉伸强度降低较多,冲击强度基本不变;800 mesh及1250 mesh滑石粉则使复合体系拉伸强度降低明显减少,同时增加体系的冲击强度,1250 mesh滑石粉体系冲击强度在滑石粉含量为20份时有极大值。线性膨胀系数结果显示,滑石粉的引入能明显降低PVC体系的线性膨胀系数,滑石粉粒径尺寸为800 mesh和1250 mesh时降低幅度比400 mesh时明显。     

石墨粒度对纸基摩擦材料摩擦磨损性能的影响

采用湿法工艺制备了4种不同石墨粒度的纸基摩擦材料, 利用惯量摩擦试验机研究了石墨粒度对摩擦力矩曲线和动、静摩擦系数及磨损率的影响; 并对不同压力和转速条件下动摩擦系数的变化趋势进行了研究. 利用扫描电子显微镜观察了磨损后纸基摩擦材料的表面形貌. 研究结果表明: 随着石墨粒度的减小, 制动时间增加, 摩擦力矩曲线中间部分趋于平直; 动、静摩擦系数减小, 磨损率降低. 同时, 动摩擦系数随着制动压力和转速的增加而减小. 循环制动过程中, 石墨粒度较小的试样制动稳定性较好. 随着石墨粒度的减小, 摩擦表面形成了润滑性能良好的固体润滑膜, 有利于提高材料的耐磨性能.