Browsing by Subject "microcrystalline cellulose"
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(2016)The main goal of this thesis was to examine the effect of the compaction speed on the compressional behaviour of two excipients, microcrystalline cellulose and starch, using an eccentric and rotary presses. First, the average weights of the tablets have changed due to the increasing speed, as the volume of die kept constant. They were grown, for eccentric press, or were reduced, for rotary press. Second, Compression force, needed to obtain tablets with similar strength, was increased during both tableting methods. The eccentric compaction was more stable regarding to the speed increase. Tablets were formed from all of the blends, with more or less success. Additionally, as a result of force increase, resulted tablets were denser and less porous because of speed expansions during eccentric press. However, the blends containing 80% or more starch were not able to form tablets during the rotary press, because of the very poor die filling. Furthermore, blend containing 60% starch has shown very poor tabletability at speeds over 34 rounds per minute. The elastic recovery of tablets was very sensitive to the speed rises and to the concentrations of excipients during the eccentric press. Tablets have demonstrated an increase in their elastic recovery values in all cases. However, the tablets with a higher concentrations of starch were significantly more sensitive to the increasing compaction velocity. According to these results, it can be concluded that the starch exhibit more elasticity than microcrystalline cellulose. The effect of magnesium stearate on tablets' properties, such as the weight and the porosity, and compaction parameters, such as ejection force have also examined. As it expected from boundary lubricants, magnesium stearate has significantly reduced the ejection force values, required for removing the tablet from the die, compared with unlubricated tablets. Additionally, tablets with lubricants were heavier and more porous. The compression force was adjusted according to the crushing strength values in rotary press. This was due to the fracture variations of such tablets during diametrical compression, which would give unreliable values of tensile strength. Moreover, elastic recovery, porosity, density values were not calculated for scored tablet, due to either the lack of punch displacement data from rotational machine or the relative complexity of measuring the volume of such tablets. If these values had been available for both machines, their comparison with respect to these parameters would be possible and the results of this thesis would have been more appropriate.
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(2021)Tablet is the most common pharmaceutical dosage form due to ease of administration, chemical and physical stability, and relatively low manufacturing cost. Direct compression is the preferred method for tablet production. Direct compression formulations typically contain a considerable amount of excipients. Therefore, excipients can have a significant effect on the tableting properties of formulations. More research is needed for better comprehension of the compression behaviour of different materials. The objective of this work was to investigate tableting properties of different excipients and their binary mixtures with two different laboratory scale tableting devices; the Gamlen® D1000 Powder Compaction Analyzer and the FlexiTab®. The excipients used were microcrystalline cellulose (MCC), lactose, mannitol, starch, and dicalcium phosphate (DCP). Different compression pressures were used to survey the compression behaviour of the excipients at a wide pressure range. In addition, potential effects of compression speed, dwell time, and lubrication method were considered. The excipients and their binary mixtures were characterised based on compressibility (solid fraction vs. compression pressure) and tabletability (tensile strength vs. compression pressure). The results obtained with the devices were compared to enhance process understanding. Based on the compressibility curves, it appeared that plastic deformation was the main compression mechanism of MCC and starch and fragmentation the main compression mechanism of lactose, mannitol, and DCP. The tabletability of MCC was excellent, and also the tabletability of mannitol was good. The tabletability of DCP was intermediate, whereas lactose and starch had inferior tabletabilities. In general, the tabletabilities and compressibilities of the binary mixtures were more or less what was expected based on the results of the individual materials. The results obtained with the different speed parameters and lubrication methods were mainly in line with the perceptions of the compression mechanisms of different materials. In overall, the results obtained in the Gamlen and FlexiTab experiments were quite similar. However, tensile strengths appeared generally slightly lower in the FlexiTab experiments. Probable explanations are the higher compression speed of the FlexiTab and differences in hardness measurements. This study indicated that the FlexiTab and Gamlen devices have different benefits. The Gamlen device is clearly very suitable for investigating tableting properties during formulation development, but the FlexiTab device has the advantages of higher compression speed and automatic powder feeding mechanism. Tabletability results were slightly better with the Gamlen, but more experiments are needed for solving the reasons (e.g. compression speed and hardness measurements). More information of the compression behaviour of different materials could be obtained by analyzing punch displacement data and by using different compression equations.
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Kuivapäällystyksen vaikutus jauheen ominaisuuksiin : mikrokiteinen selluloosa ja magnesiumstearaatti (2015)Mechanofusion is a dry coating method in which the high shear forces cause a mechanochemical reaction between the processed particles. With the approach it is possible to improve flowability of a host cohesive powder when the guest particle forming the coating is magnesium stearate. Applying mechanofusion in tablet formulations could make poor flowing large dose drug substances suitable for direct compression. However, it is well known that magnesium stearate decreases mechanical strength of the tablets and prolongs disintegration and dissolution time of tablets. A previous study, however, showed that it is possible to compress tablets from a formulation dry coated with magnesium stearate without reducing the dissolution rate. Dry coating with magnesium stearate and its effect on a plastic material, known to be sensitive for the negative effects of magnesium stearate, has not been studied previously. The aim of the study was to examine the effect of mechanical dry coating with magnesium stearate on the physical qualities and compression behaviour of a plastic material. The effect was studied by dry coating four grades of microcrystalline cellulose with different magnesium stearatecon centrations. The approach was to find an optimum between the flowability and compressibility of the powders by using different process parameters. Microcrystalline cellulose with median particle size of 23 and 78 µm were also mechanofused without magnesium stearate in order to examine whether mechanofusion itself has an effect on the properties of microcrystalline cellulose. Pure raw materials and Turbula-mixed magnesium stearate and microcrystalline cellulose blends were studied as references. Dry coating with magnesium stearate improved the flow properties of microcrystalline cellulose with D50 value less than 78 µm. Powders with D50 value greater than 144 µm, however, break down under the shear during the process and hence their flow properties were decreased. This suggests, that mechanofusion as a process is more suitable for the small particle size microcrystalline cellulose powders which, based on the results, can withstand the high-shear forces better. Mechanofusion of plain microcrystalline cellulose (D50 78 µm) revealed that the moisture content of the powder increased and stronger tablets could be compressed. Mechanofusion may cause changes to the microstructure of microcrystalline cellulose particles and to its ability to adsorb moisture. Dry coating with magnesium stearate was very effective even with short processing times and relatively low blade speeds, and it was challenging to compress hard tablets from the mechanofused mixtures. Plastic material was found to be sensitive for the negative effects of magnesium stearate, and better flow properties of a mechanofused powder resulted in weaker compressed tablets.
Now showing items 1-3 of 3