scholarly journals Characterization of Mechanical Property Distributions on Tablet Surfaces

Pharmaceutics ◽  
2018 ◽  
Vol 10 (4) ◽  
pp. 184 ◽  
Author(s):  
Ramon Cabiscol ◽  
Jan Finke ◽  
Harald Zetzener ◽  
Arno Kwade
Keyword(s):  
Surface Area ◽  
Microcrystalline Cellulose ◽  
Elastic Recovery ◽  
Compaction Pressure ◽  
Plastic Behavior ◽  
Brittle Behavior ◽  
Stiffness Anisotropy ◽  
Deformation Behaviors ◽  
Uniaxial Compaction ◽  
Local Stiffness

Powder densification through uniaxial compaction is governed by a number of simultaneous processes taking place on a reduced time as the result of the stress gradients within the packing, as well as the frictional and adhesive forces between the powder and the die walls. As a result of that, a density and stiffness anisotropy is developed across the axial and radial directions. In this study, microindentation has been applied to assess and quantify the variation of the module of elasticity ( E m o d ) throughout the surface of cylindrical tablets. A representative set of deformation behaviors was analyzed by pharmaceutical excipients ranging from soft/plastic behavior (microcrystalline cellulose) over medium (lactose) to hard/brittle behavior (calcium phosphate) for different compaction pressures. The results of the local stiffness distribution over tablet faces depicted a linear and directly proportional tendency between a solid fraction and E m o d for the upper and lower faces, as well as remarkable stiffness anisotropy between the axial and radial directions of compaction. The highest extent of the stiffness anisotropy that was found for ductile grades of microcrystalline cellulose (MCC) in comparison with brittle powders has been attributed to the dual phenomena of overall elastic recovery and Poisson’s effect on the relaxation kinetics. As a reinforcement of this analysis, the evolution of the specific surface area elucidated the respective densification mechanism and its implementations toward anisotropy. For ductile excipients, the increase in the contact surface area as well as the reduction and closing of interstitial pores explain the reduction of surface area with increasing compaction pressure. For brittle powders, densification evolves through fragmentation and the subsequent filling of voids.

Porous Al2O3/Al catalyst supports fabricated by an Al(OH)3/Al mixture and the effect of agglomerates

2005 ◽  
Vol 20 (3) ◽  
pp. 672-679 ◽  
Author(s):  
Zhen-Yan Deng ◽  
Yoshihisa Tanaka ◽  
Yoshio Sakka ◽  
Yutaka Kagawa
Keyword(s):  
Surface Area ◽  
Compaction Pressure ◽  
High Surface ◽  
High Surface Area ◽  
Catalyst Supports ◽  
Al Content ◽  
Starting Mixture ◽  
Mechanical And Electrical Properties ◽  
Uniform Microstructure ◽  
Compact Density

Porous Al2O3/Al catalyst supports were fabricated using a mixture of Al(OH)3 and Al powders, followed by pressureless sintering at a temperature of 600 °C in vacuum. Different pressures were used to prepare green compacts. High compaction pressure led to a high surface area and good mechanical and electrical properties for the sintered specimens. However, when the Al content in the sintered specimen exceeded a definite value, high compaction pressure decreased the surface area abruptly. Scanning electron microscopy observations revealed that agglomeration in the starting mixture has a significant effect on the microstructure of the sintered specimens. High compaction pressure greatly eliminated the agglomerates and led to a uniform microstructure for the sintered specimens. However, when the Al content in the starting mixture was too high, Al particles in the compacts prepared by the high pressure were largely sintered due to the high compact density so that most of the pores were closed. The present study indicates that a suitable compaction pressure is critical to obtaining superior Al2O3/Al supports.

scholarly journals PRELIMINARY INVESTIGATIONS INTO THE PHYSICOCHEMICAL AND COMPACTION CHARACTERISTICS OF MODIFIED STARCH OF DISCOREA ALATA USING DICLOFENAC SODIUM TABLET

2018 ◽  
Vol 10 (7) ◽  
pp. 66
Author(s):  
Timma O Uwah ◽  
Ekaete I Akpabio ◽  
Daniel E Ekpa ◽  
Akwaowo E. Akpabio ◽  
Jacob Godwin
Keyword(s):  
Microcrystalline Cellulose ◽  
Corn Starch ◽  
Compaction Pressure ◽  
Diclofenac Sodium ◽  
Flow Characteristics ◽  
Straight Line ◽  
Heckel Plot ◽  
The Fourier Transform ◽  
Different Sources ◽  
Water Yam

Objective: This work focused on evaluating the micromeritic and compressional properties of pregelatinized African water yam (Discorea alata) starch and its modified forms with comparison to pregelatinized corn starch and microcrystalline cellulose.Methods: Two modifications of the water yam starch were prepared; acetone dehydrated pregelatinized form (DSA) and an admixture of DSA and pregelatinized corn starch (CDSA). A third form of starch is the acetone dehydrated pregelatinized corn starch (CSA). These were used to form batches compacted as tablets using diclofenac sodium as the active moiety. Physicochemical and flow characteristics of the starch powders were elucidated, and the drug starch compatibility studies done using the Fourier transform Infra-red (FTIR) technique. Compaction studies were investigated on tablets formed at different compression pressures and Heckel plots were prepared.Results: The slope of the straight line (K) of 0.8959 was greatest for F1 while yield pressure (Py) value of 10.965 was highest for F3. These values from the Heckel plot suggest that while the tablets of control batch of microcrystalline cellulose (F4) and a batch of pregelatinized corn starch (F2) formed harder compacts, less likely deformed plastically, the Discorea alata batch (F1) and the admixed batch (F3) were likely to deform plastically. Also, the binding efficiency of the compact was significantly high (47.81%Kgscm-1) for F4 at 56.5Kpas compaction pressure, higher than that obtainable for any of the other formulations at the compaction pressures under consideration. All starches formed had similar moisture content (of 10%) despite the different sources but the interaction between the water molecule and pregelatinized water yam starch improved as revealed by viscosity(7.18mPas), hydration capacity(3.27%) and swelling index (250%) of CDSA.Conclusion: It could be concluded that pregelatinized water yam starch could be used as a substitute for corn starch or microcrystalline cellulose as a pharmaceutical excipient (binder/filler) in tablets formulation.

Plastic Deformation Behavior of Ni3X(X=Nb, Ti, Sn) Type HCP-Based Intermetallics with the Geometrically Close-Packed Structure

2002 ◽  
Vol 753 ◽  
Author(s):  
Koji Hagihara ◽  
Takayoshi Nakano ◽  
Yukichi Umakoshi
Keyword(s):  
Plastic Deformation ◽  
Basal Plane ◽  
Deformation Behavior ◽  
Plastic Behavior ◽  
Close Packed Structure ◽  
Plastic Deformation Behavior ◽  
Deformation Behaviors ◽  
Packed Structure ◽  
Characteristic Features ◽  
Similarity And Difference

ABSTBACTIn this paper, our recent results on the plastic deformation behaviors of Ni3X-type hcp-based GCP compounds, such as D0a-Ni3Nb, D019-Ni3Sn and D024-Ni3Ti, are summarized. The similarity and difference of their plastic behavior are discussed focusing on the correlation with the characteristic features of their crystal structures. The criterion for the occurrence of yield stress anomaly (YSA) by slip on the basal plane is also discussed.

scholarly journals Experimental Investigation on Flowability and Compaction Behavior of Spray Granulated Submicron Alumina Granules

ISRN Ceramics ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Abhisek Choudhary ◽  
Pandu Ramavath ◽  
Papiya Biswas ◽  
Nukala Ravi ◽  
Roy Johnson
Keyword(s):  
Relative Density ◽  
Surface Area ◽  
Flow Behavior ◽  
Compaction Pressure ◽  
High Surface ◽  
High Surface Area ◽  
Solid Loading ◽  
Alumina Powder ◽  
Flow Measurements ◽  
Spray Dried

Aqueous slurry with various solid loadings (up to 40 wt%) of alumina powder (D50 = 300 nm) with suitable rheological properties were spray dried into granules. Solid loading and feed rate of the slurry are found to have a prominent effect on the shape and size distribution of granules. Powder flow measurements exhibited a cohesive index of 28.45 signifying an extremely cohesive flow due to high surface area and irregular morphology. Finer sizes though it offers high geometrical surface area it leads to more surface contacts and hence, high interparticle friction. Spherical morphology achieved through optimum spray drying parameters significantly reduced the cohesive index to 6.45 indicating free flow behavior. Compaction studies of the spray-dried granules and corresponding plot of relative density versus compaction pressure revealed an agglomerate strength of 500 MPa followed by a plateau-like behavior reaching a maximum in the relative density of 59%-60% of the theoretical values.

Pretreatment of microcrystalline cellulose flakes with CaCl2 increases the surface area, and thus improves enzymatic saccharification

2008 ◽  
Vol 343 (7) ◽  
pp. 1232-1236 ◽  
Author(s):  
Ken Tokuyasu ◽  
Mine Tabuse ◽  
Maki Miyamoto ◽  
Junko Matsuki ◽  
Koichi Yoza
Keyword(s):  
Surface Area ◽  
Microcrystalline Cellulose ◽  
Enzymatic Saccharification

Microstructures of Nanocellulose and Reinforcement in Nitrile Butadiene Rubber (NBR) Composites

2017 ◽  
Vol 264 ◽  
pp. 124-127
Author(s):  
Mohamad Nurul Azman Mohammad Taib ◽  
Nurhidayatullaili Muhd Julkapli ◽  
Wageeh Abdulhadi Yehye ◽  
Sharifah Bee O.A. Abdul Hamid
Keyword(s):  
Hydrogen Bonding ◽  
Acid Hydrolysis ◽  
Surface Area ◽  
Field Emission ◽  
Microcrystalline Cellulose ◽  
Mechanical Performance ◽  
Mineral Acid ◽  
Butadiene Rubber ◽  
Rubber Composites ◽  
Nitrile Butadiene Rubber

This study was done to investigate the microstructures of nanocrystalline cellulose (NCC) after hydrolysis with mineral acid concentrated. The optimum NCC was achieved through acid hydrolysis and the NCC was used as a reinforcement in nitrile butadiene rubber composites. The Field Emission Scanning Microscopy (FESEM) was used to study the structures and surfaces of the NCC and composites produced. The NCC that was synthesis from microcrystalline cellulose (MCC) found to be more individual and agglomerated due to hydrogen bonding between the NCCs, the more individual NCC produced would create more surface area to be bonded with NBR as a reinforcement. More surface area of NCC was good to create physical bonding with NBR and increase mechanical performance of composites. The NCCs in NBR composite found to form agglomeration caused by different properties that exhibited by both materials. This can restrict and reduce the performance of composite produced. A combination of these materials can be used as a reinforcement but need more attention on the modification to make these materials more compatible. Further research can be done to find the best way to prevent agglomeration between these both materials.

Elastic recovery and surface area changes in compacted powder systems

1974 ◽  
Vol 9 (5-6) ◽  
pp. 287-290 ◽  
Author(s):  
N.A. Armstrong ◽  
R.F. Haines-Nutt
Keyword(s):  
Surface Area ◽  
Elastic Recovery

scholarly journals Mechanical Properties of Natural Fiber Reinforced Foamed Concrete

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3060 ◽  
Author(s):  
Joaquin F. Castillo-Lara ◽  
Emmanuel A. Flores-Johnson ◽  
Alex Valadez-Gonzalez ◽  
Pedro J. Herrera-Franco ◽  
Jose G. Carrillo ◽  
...  
Keyword(s):  
Natural Fiber ◽  
Compressive Loading ◽  
Polypropylene Fiber ◽  
Alkaline Treatment ◽  
Plastic Behavior ◽  
Fiber Reinforced ◽  
Brittle Behavior ◽  
Tension Tests ◽  
Foamed Concrete ◽  
Air Void

The mechanical characterization of plain foamed concrete (PFC) and fiber-reinforced foamed concrete (FRFC) with a density of 700 kg/m3 was performed with compression and tension tests. FRFC was reinforced with the natural fiber henequen (untreated or alkaline-treated) at volume fractions of 0.5%, 1% and 1.5%. Polypropylene fiber reinforcement was also used as a reference. For all FRFCs, the inclusion of the fibers enhanced the compressive and tensile strengths and plastic behavior, which was attributed to the increase of specimen integrity. Under compressive loading, after the peak strength, there was no considerable loss in strength and a plateau-like regime was observed. Under tensile loading, the fibers significantly increased the tensile strength of the FRFCs and prevented a sudden failure of the specimens, which was in contrast to the brittle behavior of the PFC. The tensile behavior enhancement was higher when treated henequen fibers were used, which was attributed to the increase in the fiber–matrix bond produced by the alkaline treatment. The microscopic characterization showed that the inclusion of fibers did not modify the air-void size and its distribution. Higher energy absorption was observed for FRFCs when compared to the PFC, which was attributed to the enhanced toughness and ductility by the fibers. The results presented herein warrant further research of FRFC with natural henequen fibers for engineering applications.

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