Compression mechanics of pharmaceutical aggregates : Studies on the tabletting of spheronised aggregates with varying composition and porosity
Abstract: The thesis investigated the tabletting behaviour of aggregates of different porosity and material composition, and focused on the role of the compression mechanics of the aggregates as a link between their structure and composition and the structure and functionality of tabletsformed from them. The aggregates studied all responded to compression by deformation and densification. Furthermore, the deformation behaviour of aggregates was found to consist of three deformation characteristics: The capacity for deformation, that is the maximum amount of deformation that can occur when aggregates that are compressed in a tabletting die.The mode of deformation, that refers to the ability of aggregates in a bed to conform to the surfaces of adjacent aggregates during compression, thus minimising the intergranular pore volume. If this ability is well developed, the aggregates are said to exhibit a surface oriented mode of deformation, as opposed to a bulk oriented mode of deformation.The resistance to deformation, that is the magnitude of the shear stress during tabletting that is associated with aggregate deformation.If aggregates have a high capacity for deformation, the total densification of the tablet structure will be high. A surface oriented mode of deformation during compression will result in a dense packing of aggregates in the formed tablets. The resistance to deformation will decide the pressure range in which the greatest changes to the tabletstructure will occur. The intergranular pore structure in tablets was shown to be a controlling factor for the mechanical strength of the tablets.The thesis contributes to the mechanistic understanding of the tabletting process for aggregates as well as the methodology in the field of research in a way that may be of use for the development of the solid dosage forms of tomorrow.
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