Research Article A Comparative Study of the Compaction Properties of Binary and Bilayer Tablets of Direct Compression (original) (raw)
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Purpose: To comparatively evaluate the tableting properties of binary mixtures and bi-layer tablets containing plastic deformation and brittle fracture excipients. Methods: Binary mixture and bi-layer tablets of microcrystalline cellulose (MCC), ethyl cellulose, anhydrous lactose and dextrate were prepared by direct compression and the effect of compaction pressure on the materials was investigated by scanning electron microscopy (SEM). True, bulk and tap densities of excipients were determined. Furthermore, Heckel equation and Carr’s index were used to analyze the compression behavior of the tablets. Results: The flowability of dextrate, based on Heckel and Carr’s Index data, was superior to that of other powder excipients tested. No significant difference was observed between the tensile strength of binary and bi-layer tablets of the same composition. However, the tensile strength of binary and bi-layer tablets of different compositions varied significantly (p < 0.001), e.g., the tensile strength of microcrystalline cellulose (MCC)/ethyl cellulose (EC) tablets (50/50) was 1.77 MPa while that of MCC/dextrate at 50/50 composition was 1.47 MPa. Conclusion: Binary mixture and bi-layer tablets show similar behavior when formulated using excipients of similar deformation properties. However, their behavior changes when excipients with different deformation properties are blended together. Keywords: Binary mixture, Bi-layer tablet, Brittle fracture, Plastic deformation, Tensile strength.
A comparative study of compaction properties of binary and bilayer tablets
Powder Technology, 2009
Bi-layer tablets have been developed to achieve controlled delivery of different drugs with pre-defined release profiles. However, the production of such tablets has been facing great difficulties as the layered tablets are prone to fracture. In this paper, the compaction behaviour of binary mixtures and bilayer tablets of two common pharmaceutical excipients, Microcrystalline cellulose and lactose, is investigated. The effects of compositions and compaction pressure on the compaction behaviour of binary matrix mixtures and bilayer tablets are also explored. The delamination phenomena during the manufacturing of bilayer tablets and fracture patterns of tablets subjected to diametrical compression are examined using X-ray computed tomography. The mechanical properties of binary and bilayer tablets of the same composition were also determined and compared. It has been shown that for binary and bilayer tablets with the same composition, the apparent crush strength of these binary and bilayer tablets measured from diametrical compression tests were generally comparable for the powders considered in this study. It was also found that, using the same compaction process, the relative densities of the tablets were generally different when different compositions were used, especially when the maximum compression pressure is relatively low.
The mechanical properties of model-compacted tablets
Journal of Materials Science, 2008
In this study, the compressive strength of tablets made with salt, starch and fat was investigated. The strength was found to increase with compaction pressure, up to a maximum value where further increase in the compaction pressure led to no increase in the strength. The maximum strength corresponded to the point where zero porosity was obtained during the compaction process. However, because of the elastic rebound of the tablets after ejection, the maximum strength corresponded to non-zero final tablet porosities which varied between the materials. For this reason, the use of the density occurring during the compaction process appeared to provide a more reliable comparison between the materials. A simple linear mixing rule did not hold in characterising the strength in the salt:starch:fat systems. However, two regimes were observed depending on the salt volume fraction. At low salt volume fractions, the effect of the salt was negligible. After a certain critical salt volume fraction, increasing the salt led to an increase in the strength. Finite element simulations based on X-ray microtomography images of the tablets suggested that in the first regime, the stresses due to the salt particles were localised but in the second regime, stress-bearing networks were formed between the salt particles.
The degree of deformation and densification of pellets during compression have been quantified. The relationship between the degree of deformation of the pellets and their compactability were also studied. Two sets of pellets of microcrystalline cellulose, showing a marked difference in intragranular porosity, were prepared by extrusionspheronization. The pellets were mixed with a lubricant and compacted at a series of applied pressures. The individual pellets were retrieved after compression by tablet deaggregation and the porosity (densification behaviour) and dimensions (deformation behaviour) of the retrieved pellets were determined. Tensile strength of compacts prepared of unlubricated pellets was also determined. The incidence of pellet fragmentation was almost non-existent during the compression for both sets of pellets. The low porosity pellets showed only limited local permanent deformation during compression and the pellet porosity was unaffected by the compression. The high porosity pellets showed both a high compression-induced change in shape and a marked decrease in pellet porosity. Tensile strength values of tablets of unlubricated pellets indicated that a marked bulk structure deformation of the pellets was necessary for the formation of intergranular contacts of a high bonding force in the compact.
Drug Development and Industrial Pharmacy, 2013
The repeated compaction of Avicel PH101, dicalcium phosphate dihydrate (DCP) powder, 50:50 DCP/Avicel PH101 and Starch 1500 was studied using an instrumented laboratory tablet press which measures upper punch force, punch displacement and ejection force and operates using a V-shaped compression profile. The measurement of work compaction was demonstrated, and the test materials were ranked in order of compaction behaviour Avicel PH1014DCP/Avicel PH1014Starch4DCP. The behaviour of the DCP/Avicel PH101 mixture was distinctly non-linear compared with the pure components. Repeated compaction and precompression had no effect on the tensile fracture strength of Avicel PH101 tablets, although small effects on friability and disintegration time were seen. Repeated compaction and precompression reduced the tensile strength and the increased disintegration time of the DCP tablets, but improved the strength and friability of Starch 1500 tablets. Based on the data reported, routine laboratory measurement of tablet work of compaction may have potential as a critical quality attribute of a powder blend for compression. The instrumented press was suitable for student use with minimal supervisor input.
Tensile strength of tablets containing two materials with a different compaction behaviour
International journal of pharmaceutics, 2000
The tensile strength of tablets compressed from binary mixtures is in general not linearly related to the strength of tablets prepared from single materials; in many cases it shows a decreased tensile strength relative to interpolation. The materials used in this study, sodium chloride and pregelatinised starch, are both plastically deforming materials, but have a different densification and relaxation behaviour. The yield pressure of the binary mixtures shows an almost linear relationship. As an effect of their lower yield pressure, starch particles yield earlier than sodium chloride particles. The following enclosure prevents some sodium chloride particles to yield or crack. The relaxation of the tablets is higher than the relaxation calculated by linear interpolation of the relaxation behaviour of the two pure materials. The difference between the measured porosity expansion and the data obtained by linear interpolation can be considered as a measure for the reduced interparticle...
Compaction Mechanism and Tablet Strength of Cellactose®
Jordan Journal of Pharmaceutical Sciences
Objective: This paper describes the differences, in relation to compaction properties, between Microcrystalline Cellulose (MCC) and α-lactose monohydrate physical mixture, and microcrystalline cellulose co-processed with α-lactose monohydrate (Cellactose ®). Methods: The different compaction parameters were not only studied on the pure materials, but also on the lubricated powders with magnesium stearate. Results: Magnesium stearate does not facilitate the densification of either the physical mixture or Cellactose during compaction. The difference in tablet relaxation of the physical mixture and Cellactose indicates that the negative effect of the lubricant on the interparticle bonding of Cellactose particles is smaller compared to its effect on the physical mixture particles. However, a larger increase in tablet relaxation at a high compression speed was found for both Cellactose and the physical mixture at different lubricant concentrations. Accordingly, the decrease in tablet str...
Crystallinity index of microcrystalline cellulose particles compressed into tablets
International Journal of Pharmaceutics, 1995
The crystallinity index of compressed microcrystalline cellulose particles has been estimated using 13C CP/MAS NMR and photoacoustic FTIR. The results indicate a slight initial increase in crystallinity followed by a decrease as the compaction pressure increases. The initial increase is explained as a transformation of strained structures in cellulose particles into more ordered forms as a result of the initial compression. At higher compaction pressures the crystallinity begins to decrease. This change in crystallinity seems to be larger on the tablet surface than in the tablet bulk and even larger at the tablet perimeter surface than on the top or bottom surfaces of the tablet. Our explanation for these findings is that these differences reflect different levels of shearing forces acting on different parts of the tablet during compaction.
Drug Development and Industrial Pharmacy, 2010
Objective: The aim of this work is to study the effect of compaction on the specific surface area of tablets composed of various pharmaceutical materials (microcrystalline cellulose, lactose, and anhydrous calcium phosphate) compacted under seven degrees of compaction pressure. Methods: In a first part, the influence of the deformation behavior of the compacted materials on the evolution of the specific surface area is observed. In a second part, the brittle and ductile abilities of the materials are calculated using the specific surface area values. The experimental results are used to calculate the number and the force of interparticulate bonds inside the tablet. Results and Discussion: Tablets made of microcrystalline cellulose, which deform plastically, have specific surface areas that fall under pressure. In the case of lactose, the tablet specific surface area first increases to reach a maximum value at a pressure of 150 MPa. At higher pressure, however, the specific surface area decreases. The specific surface area of tablets composed of anhydrous calcium phosphate consistently increases, whatever the compaction pressure applied. Moreover, the evolution of the specific surface area is correlated with the tensile strength of the corresponding tablets. The number and the force of interparticulate bonds make it possible to classify the materials according to their deformation behavior and to quantify their ability to form cohesive tablets.