Ajit Mujumdar’s research while affiliated with Tokyo University of Agriculture and Technology and other places

What is this page?


This page lists works of an author who doesn't have a ResearchGate profile or hasn't added the works to their profile yet. It is automatically generated from public (personal) data to further our legitimate goal of comprehensive and accurate scientific recordkeeping. If you are this author and want this page removed, please let us know.

Publications (21)


Fig. 1. SEM images of primary particles of (a) milled lactose and (b) milled IBP. 
Fig. 2. Size distribution of primary particles. 
Table 2 Tensile strength of granules (n = 10)
Fig. 3. Schematic diagram of the mixing apparatus. 
Table 4 Hardness of tablet from compacted granules (n = 20)

+12

Improvement of sticking tendency
  • Data
  • File available

October 2014

·

325 Reads

·

Ajit Mujumdar

·

Shun Urabe

·

[...]

·

Download

Environmentally benign dry mechanical mixing of nano-particles using magnetically assisted impaction mixing process

May 2011

·

78 Reads

·

14 Citations

Powder Technology

The effectiveness of magnetically assisted impaction mixing (MAIM), an environmentally benign mechanical process, in mixing SiO2+TiO2 and SiO2+Al2O3 nanoparticle mixtures has been examined. Experiments were carried out at different magnet-to-sample weight ratios, processing times, and magnet sizes. The homogeneity of mixing (HoM) was evaluated at the micron scale using field-emission scanning electron microscopy and energy dispersive X-ray spectroscopy, and at sub-micron scale through electron energy loss spectroscopy and transmission electron microscopy. The HoM improved with an increase in the magnet-to-sample weight ratio and processing time, and a decrease in the magnet size; over the range of conditions tested, the HoM was found to depend on the product of processing time and the number of magnets per unit powder mass. Optimized MAIM process achieved HoM values that were comparable to those attained with Rapid Expansion of Supercritical or High-Pressure Suspensions and sonication of a suspension of the nanoparticles in supercritical CO2.


Near-Infrared Spectroscopy for the In-Line Characterization of Powder Voiding Part II: Quantification of Enhanced Flow Properties of Surface Modified Active Pharmaceutical Ingredients

July 2010

·

44 Reads

·

25 Citations

Journal of Pharmaceutical Innovation

In this work, dry-particle coating was used to modify the surface properties of active pharmaceutical ingredients (APIs) having extremely poor flow properties. Near-infrared (NIR) spectroscopy was utilized as a novel approach to characterize the improved flow behavior of APIs and their blends. Acetaminophen and ibuprofen were coated with nano-sized silica at two different coating levels (0.5% and 1% w/w of the API) in dry-particle coating devices viz. magnetically assisted impaction coater (MAIC) and Hybridizer. Surface modified (dry coated) APIs were then blended with excipient (spray dried lactose monohydrate) in a V-blender. As a baseline comparison to dry coating, the silica addition was also accomplished by two commonly used industry methods, i.e., passing a portion of API with silica through a sieve (sieve blending method) or blending a portion of API powder with silica in a V-blender (preblending method). Flow results showed that dry particle coated acetaminophen as well as ibuprofen blends performed significantly better than uncoated API blends at higher API concentrations. In addition, examination of the flow intensity from NIR spectra (inverse signal to noise ratio of spectra) and its standard deviation revealed that dry particle coated blends showed better uniformity of flow as compared to the other methods. Angle of repose measurements corroborated these results, showing that the majority of the blends prepared from coated APIs stayed in either passable or fair category. KeywordsDry-particle coating-Flow improvement of APIs-Flow uniformity-Near-infrared spectroscopy-Angle of repose-Flow additives-Surface modification-Nano silica


Simultaneous Particle Size Reduction and Surface Modification to Enhance Flowability of APIs

November 2009

·

29 Reads

In this work simultaneous size reduction and surface coating is considered in order to increase the dissolution of drugs while maintaining their flowability. This is accomplished by coating nano-sized, silica guest particles on the surface of API particles, while they are reduced in size through Fluid Energy Mill (FEM). Two types of APIs are used: acetaminophen and ibuprofen. Two types of nano-silica are applied. One is hydrophilic silica M5-P, another one is hydrophobic silica R-972 pharma. Both are pharma grade excipients. Particle size distributions before and after the FEM process are investigated. The results show that with the increase of grinding pressure, the mean particle size decreases. For ibuprofen, before the process the mean particle size is about 100 microns, after the process the mean particle size decreases to about 10 microns. Angle of repose in various conditions is tested, indicating acceptable flow for such fine particles. Ibuprofen with 1.0 wt % of silica M5-P coated show the best flowability. SEM images confirmed the extent of surface modification with silica. Another objective of this work is to produce high content API with good dispersion and flowability, which may be suitable for inhalation application. Hydrophobic biodegradable material (such as L-leucine) is applied instead of using nano-sized particles to modify the particle surface. Proposed approach results in simultaneous particle size reduction and surface modification. The particle size is reduced and at the same time the flowability of powders is improved. Powders in size range 1-10 microns are produced with high API content (>95 %), having good dispersion and flowability without use of nano-particles.


The Effect of Surface Modification On the Triboelectric Characteristics of Pharmaceutical Powders

November 2009

·

26 Reads

Powder handling processes involve contact of particles with each other and the surface of the transporting vessel, which normally lead to electrostatic charging of the particles. In many cases the electrostatic charging will affect the behavior of the powder during the handling process. This study is to understand the triboelectric characteristics of surface modified as compared to original untreated pharmaceutical active ingredient (API) powders. The triboelectric charging effect was quantified at different relative humidities (RH) and different surface coating levels; using stainless steel and polycarbonate as the contact surfaces. The results show that for untreated powders, the particles charge less at lower RH and charge more at high RH; while for the surface modified powders, the opposite is true. BET surface area measurement was used to determine the specific surface area of the particles, which is then used to calculate the charge density. Inverse Gas Chromatography (IGC) is used to determine the electron acceptor-donor characteristics and correlated with ones obtained from the triboelectric experiment for the unmodified and modified particles. Meanwhile, flow characterization results of these powders show a significant improvement in flow behavior that accompanies decrease of triboelectric charging for the surface modified powders.


Characterization of Pharmaceutical Powders Modified by Dry Coating

November 2009

·

18 Reads

Engineered particles, which are surface modified via dry coating have been shown to have improved flow and handling properties, and hence are very useful for a number of industrial applications. Recent work in our group has indicated that dry coating makes it possible to impart improved flowability for blends with very high API contents (higher than 75 %) even for very cohesive micronized API powders. This is very useful for pharmaceutical processing including flow, handling and downstream processing. Although it is clear that these surface modified powders flow better as indicated by reduced angle of repose and faster or more uniform flow out of a funnel, there is an unresolved issue; the extent of powder attrition during surface modification and the influence of size reduction on flow properties that are specifically relevant to industry practice. Acetaminophen and ibuprofen are considered as model active pharmaceutical ingredients (APIs), and are surface modified via dry coating of nano-additives in several dry coating devices. The study considers use of hydrophobic as well as hydrophilic nano-additives. The resulting powders are analyzed for their particle size distribution, coating coverage, and dispersibility; the latter is evaluated using the Sympatec Helos/Rodos system under varying dispersion conditions. In addition, a suite of techniques are employed for powder flow and other properties which are important for large scale pharmaceutical manufacturing. Extensive powder flow property characterization is done, ranging from novel methods such as vibrated packed density measurements to industry standard technique such as shear testing via the Schulze tester. In addition, other powder properties such as sticking tendency and electrostatic properties are evaluated, and several flow testers are also employed, including the Aeroflow, Freeman Rheometer, and the Hosokawa Powder Tester. The results of these tests are compared with those for untreated API powders in order to examine the influence of surface modification on property enhancements.


Assessment of the Influence of Surface Modified Pharmaceutical Powders On Dissolution and Mechanical Properties of the Tablets

November 2009

·

16 Reads

Engineered particles, which are surface modified via dry coating have been shown to have improved flow and handling properties, and hence are very useful for a number of industrial applications. Recent work in our group has indicated that dry coating makes it possible to impart improved flowability for blends with very high API contents (higher than 75 %) even for very cohesive micronized API powders. This is very useful for pharmaceutical processing including flow, handling and downstream processing. However, the influence of such surface modification on downstream product properties has not been well investigated. In this work, preparation, characterization and applications of such engineered particles to pharmaceutical applications is considered, and in particular, the influence of such powders on tablet properties, including dissolution is examined. Acetaminophen and ibuprofen are considered as model active pharmaceutical ingredients (APIs), and are surface modified via dry coating of nano-additives. The study considers use of hydrophobic as well as hydrophilic nano-additives. Tablets are prepared for two types of API loadings, low API concentration and high API concentration. Drug release profile and disintegration time from these tablets are examined and compared with that of tablets made from comparable formulations containing uncoated APIs. In addition, mechanical properties of these tablets are evaluated, including strength, weight and content uniformity, friability, density, hardness, etc.


Fluidized bed film coating of cohesive Geldart group C powders

February 2009

·

178 Reads

·

51 Citations

Powder Technology

The difficulty of coating cohesive Geldart group C powders in a conventional fluidized bed is attributed to strong inter-particle force between fine particles leading to poor fluidization behavior. Dry coating approach involving deposition of nanosize particles on the surface of group C powders is considered to reduce the interparticle force and improve the fluidization behavior of fine powders. Polymer film coating at an individual particle level is achieved on these pre-coated fine powders in a commercially available spouting fluidized bed (MiniGlatt). The effect of operating conditions such as inlet air temperature, polymer concentration, polymer weight ratio, water percentage in solvent and spray rate of coating solution on the quality of film coating are investigated. Experimental results demonstrate that the quality of film coating goes down as polymer concentration in coating solution goes higher, whereas the lower inlet air temperature is found to enhance polymer film generation and coating quality. It is also observed that the higher polymer weight ratio promotes agglomeration without affecting the coating quality to a great extent. An optimum water ratio in acetone-water solvent as well as spray rate can be optimized to achieve superior coating quality with acceptable agglomeration ratio.


DEM simulation of polydisperse systems of particles in a fluidized bed

February 2009

·

112 Reads

·

35 Citations

Particuology

Numerical simulations based on three-dimensional discrete element model (DEM) are conducted for mono-disperse, binary and ternary systems of particles in a fluidized bed. Fluid drag force acting on each particle depending on its size and relative velocity is assigned. The drag coefficient corresponding to Ergun’s correlation is applied to the system of fluidized bed with particle size ratios of 1:1 for the mono-disperse system, 1:1.2, 1:1.4 and 1:2 for the binary system and 1:1.33:2 for the ternary system by keeping total volume and surface area of the particles constant. Results indicated that a reasonable estimation of drag force based on individual particle diameters as compared to that of the mean diameter of the particles is achieved in the fluid cells. The total translational kinetic energy of the particles is found to increase as the particle size ratio increases, suggesting an enhanced momentum transfer in polydisperse particle systems. Systems with wide particle size distribution exhibited higher particle velocities around bubbles, resulting in faster bubble growth and its subsequent rise through the fluidized bed.


Properties and Characterization of Pharmaceutical Powders Modified by Dry Coating

November 2008

·

24 Reads

Dry coating is an innovative technique in which nano particles are mechanically coated onto the surface of larger (from a micron to few microns) host particles to impart useful properties to the final product, which are engineered particles. Dry coated engineered particles can have improved flow and handling properties, and hence are very useful for a number of industrial applications. In this paper, we present preparation, characterization and applications of such engineered particles to pharmaceutical applications. Positron Emission Particle Tracking (PEPT) was used as a tool to determine the differences in mobility of powders with no additive compared to powders that had been coated with a specific level of additive using the Magnetically Assisted Impaction Coater . PEPT is a tool derived from the positron emission tomography (PET) nuclear technology used in medical imaging. Instead of imaging as with PET, PEPT uses the same triangulation principle to track a positron emitting tracer particle. The triangulation principle works using the pairs of gamma rays emitted from the particle to track the exact location of the particle at that time. Previous results indicate that increasing the level of additive caused an increase in the flowability and mobility of the powder. PEPT was used as a tool to quantify the increase in mobility of the powder.


Citations (11)


... Oppositely, the intensity of segregation can differentiate between high-quality mixtures, but offers limited value for low-quality mixtures. In this study, we differentiate between multiple high-quality mixtures through the intensity of segregation To et al. 2009;Scicolone et al. 2008) determined using EDS results at 400 random points on the smooth surface of a tableted powder sample. Coarse-scale mixtures are characterized by the scale of segregation of EDS-based maps on elemental concentration with respect to spatial locations, which is a novel addition to the analysis of nanopowders mixtures. ...

Reference:

Nanoparticle mixing through rapid expansion of high pressure and supercritical suspensions
Mixing of Nanosized Particles by Magnetically Assisted Impaction Mixing in Dry and Fluid Suspension

... Ibuprofen is a highly potential active pharmaceutical ingredients (API) of non-steroidal anti-inflammatory drugs (NSAIDs) [8] and cannot afford to have residual solvents in the formulations [9]. However, there are limited reports focusing on racemic ibuprofen in melt granulation [5,10]. ...

Improvement of sticking tendency of granules during tabletting process by pressure swing granulation
  • Citing Article
  • July 2007

Powder Technology

... This method utilizes water or organic solvents as a coating carrier to form an inert barrier on the powder surface, enhancing its corrosion resistance, wear resistance and adhesion. However, the waste liquids containing volatile organic compounds pose concerns about environmental pollution [22], causing their decreased usage in recent years. Dry powder coating involves electrostatically adsorbing the coating material uniformly onto the surface of the object, followed by a curing process at high temperatures [23]. ...

Improvement of humidity resistance of magnesium powder using dry particle coating
  • Citing Article
  • February 2004

Powder Technology

... To give an example, many researchers have utilized the water modeling RTD data of Singh and Koria (1993) to validate their mathematical models. However, it could be found that some of the simulations (Jha et al., 2003;Shinde et al., 2006;Tripathi and Ajmani, 2005), which used the density-decoupled STE-method have shown a right side shifted RTD curve compared to the experimental RTD curve. Moreover, in the experiment of Singh and Koria (1993), the tundish had a boat like geometry without any flow control devices. ...

FLUID FLOW CHARACTERISTICS AND RTD ANALYSIS OF A SINGLE STRAND TUNDISH
  • Citing Article

... Magnetically assisted impaction mixing (MAIM) is suitable even for processing nanoparticle mixtures [157]. In this environmentally benign mechanical process, the homogeneity of the resulting mixture approaches levels that are otherwise difficult to achieve. ...

Environmentally benign dry mechanical mixing of nano-particles using magnetically assisted impaction mixing process
  • Citing Article
  • May 2011

Powder Technology

... Despite its obvious advantages, the dry coating process typically uses an excess of coating material accompanied by high energy consumption to achieve highly uniform and consistent coatings. Several studies have been carried out to provide fundamental understanding of the factors governing dry powder coating performance (Alonso et al., 1989;Dave et al., 2003;Nguyen et al., 2014;2016;Deng et al., 2018;Tamadondar et al., 2018). The effect of particle interfacial energies and mixing energy input on dry powder coating efficiency has been investigated by Tamadondar et al. (2018) via Discrete Element Method (DEM) simulations of a Couette cell. ...

Numerical simulation of dry particle coating processes by the discrete element method
  • Citing Article
  • November 2003

Advanced Powder Technology

... Over the last few decades, significant efforts have been devoted to leveraging ML approaches, such as support vector machines [28,29], Gaussian processes [30,31] and artificial neural networks [32,33,34,35] to model physical processes. Many of these approaches operate as data-driven mechanisms, treating ML as a black-box tool. ...

Artificial Neural Network (ANN) Model for Prediction of Mixing Behavior of Granular Flows
  • Citing Article
  • May 2007

International Journal for Computational Methods in Engineering Science and Mechanics

... Binary mixtures generate extremely complex flow processes during gas-solid two-phase flow, so many scholars have conducted a large number of numerical simulation studies on the fluidization behavior of binary mixtures in fluidized beds using CFD-DEM methods to better analyze the particle characteristics. Tagami et al. [29] performed numerical simulations of single, binary, and ternary particle systems in a fluidized bed using a three-dimensional discrete element model, assigning the trapping force acting on each particle according to its size and relative velocity. Ma et al. [30] investigated the fluidization behavior of binary mixtures consisting of different ratios of bar particles and spherical particles using the CFD-DEM model. ...

DEM simulation of polydisperse systems of particles in a fluidized bed
  • Citing Article
  • February 2009

Particuology

... Fine powders are cohesive unless they are specifically engineered to have reduced cohesion and improved flow, packing and dispersibility, for example, pharmaceutical powders with significantly enhanced flowability and bulk density after dry coating [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Generally, smaller the particle, poorer its flow, see for example all particles under 30 lm sized active pharmaceutical ingredients (APIs) and excipients in Table 1 (note that suggested FFC based flow regimes are: FFC < 2 -very cohesive, 2 < FFC < 4cohesive, 4 < FFC < 10 -easy flowing, and FFC > 10 -free flowing) [18]. ...

Near-Infrared Spectroscopy for the In-Line Characterization of Powder Voiding Part II: Quantification of Enhanced Flow Properties of Surface Modified Active Pharmaceutical Ingredients
  • Citing Article
  • July 2010

Journal of Pharmaceutical Innovation

... Such calculations make it possible to thoroughly cover numerous physical parameters and material conditions that would otherwise be empirically inaccessible. A considerable number of research pertaining to the thermodynamic and mechanical properties of RuAl and other alloys based on RuAl has been carried out [28][29][30][31][32][33][34]. The initial steps in the study of the physical properties of the RuAl intermetallic compound include the calculation of the electron structure and equilibrium parameters of the alloy. ...

Microstructural Evolution and Hardening Behaviour of Cast and Heat-treated Ru-Al and Ru-Al-Ni alloys
  • Citing Article
  • February 2008

Metals and Materials International