Browsing by Subject "segregation"
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(2011)Segregation or demixing of particle systems is a phenomenon where one component of a homogeneous powder mixture tends to separate from the other components. The segregation tendency of powder depends on the characteristics of particles, environmental conditions and interactions between particles. A huge number of segregation mechanisms are presented in literature and even small differences between the properties of particles and particle interactions can lead to a completely different segregation mechanism. The segregation phenomenon is very essential from the perspective of pharmaceutical industry. However, the phenomenon is not yet sufficiently well known in order for segregation to be systematically avoided. Current research on segregation is largely based on learning through trial and error. Therefore, innovative research methods are needed to understand the true segregation phenomenon. The purpose of the experimental part was to develop and basic test the method of testing the segregation behavior of different particle systems and use this method to examine the segregation behavior of pharmaceutical mixtures of granules and pellets. The aim was to prove that the operating principle of the developed Babel-device is suitable for examining the segregation behavior of particle systems, but the trials carried out mainly consisted of method and device testing. The problems were composed of the limitations imposed by the Babel-device, particle electrification and particle interactions. Linear approaches used were insufficient for creating segregation by the Babel-device. Convection resulting from vertical shaking prevented the generation of segregation. In conclusion, we can say that the Babel-device measures well and reproducibly, and it is able to distinguish different particle sizes and different particle size distributions from each other. The development aim of the device would be to obtain a more visible segregation in the powder mixture as a result of shaking. Thus, we would be able to draw conclusions from the segregation behavior of the powder mixture and the prevailing segregation mechanisms in the system. Further development of the device and the method could provide useful additional information which would contribute to better understanding of the phenomenon of segregation.
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(2018)Tablet manufacturing requires both high-quality equipment and powder blend with high flowability and compactability and low segregation tendency. The process is complex and tablet formation process still remains not fully understood. Adequate powder flow is a necessity for the pharmaceutical manufacturing process, i.e., powder flowability and flow properties play a great role when designing manufacturing processes for solid dosage forms. As such, the powder characteristics need to be investigated. However, one property is seldom enough to predict the flowability of a powder in specific processes and different test methods need to be used to fully understand the tableting performance of a particular powder. It is crucial to know how the assessed properties reflect the manufacturing conditions. The need for test batches and the use of empirical testing still exists despite the numerous powder characterization tests available. The main aim of the study was to understand the influence of material properties, flow properties and segregation tendencies on both the processability of a formulation during tablet compression and the critical quality attributes, such as mass, tensile strength and dose uniformity of the final drug product. Additionally, testing of an in-line NIR method to observe the homogeneity of the powder inside the force feeder right before the compression step and transmission Raman as an at-line method for tablet content were also evaluated. A number of powder characterization tests were employed in order to fully understand the impact of the formulation on the process performance. Three formulations with different particle size of the active substance and mannitol were used throughout the study. Both the sifting segregation and fluidization segregation tests’ results predicted the formulations’ tabletability particularly well. Fluidization segregation test predicted the changing composition of the formulation throughout tableting whereas sifting segregation results showed the constantly fluctuating API concentration in the manufactured tablets. Moreover, the Raman results confirmed the tablets of variable content despite the offset caused by the different particle size of the raw materials used. The functionality of the NIR in the force feeder was tested successfully. The residence time distribution could be determined at a sufficient level to point out tablets of a bad quality from the batch on grounds of the NIR data. Results from the powder flow property tests were rather conflicting. Angle of repose, Carr’s index and volume flow rate gave the best characterizing results, whereas the mass flow rate, shear test with higher normal stress in pre-shear gave the worst results, considering the experienced flow character of the formulations. As stated above, different flow property tests may give conflicting result, and hence, it is crucial to know which results are the most relevant ones. Furthermore, the right settings for the test should be known to gain applicable results, best exemplified by the shear cell test.
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