Al-Nasassrah, Muhammed Ali; (1997) Mechanical Properties of Multicomponent Tablets. Doctoral thesis (Ph.D.), University College London (United Kingdom).

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Abstract

Five molecular weight of polyethylene glycols (PEGs), five analogues of benzoic acid as model drug molecules and five direct compression excipients (Avicel PH-200, Starch-1500, Tablettose, Emcompress and povidone) were characterised from mechanical behaviour view point. The influence of the mechanical parameters on the consolidation and mechanical strength of binary mixtures of these components was assessed. A relationship was found between the tensile strength, Young's modulus and the critical stress intensity factor. The increase in the molecular weight of the PEGs was found to reduce the brittleness of the material, a linear relationship tend to occur between the molecular weight of PEGs and the critical stress intensity factor. A tableting machine was instrumented using piezoelectric force transducers and used to prepare flat faced cylindrical tablets from mixtures of the two model drugs (PEGs and parabens) mixed in different proportions with the direct compression excipients. The tensile strength, by diametral compression, for the different mixtures was determined, and the ability to predict compact strength of multicomponent systems was investigated. The tensile strength of powder mixtures with PEGs was found to be dependent only on the proportion of the polymer in the mixture. However, for mixtures with Tablettose, the KIc was found to influence the tensile strength. For povidone mixtures, the Young's modulus showed a significant influence on the tensile strength of the mixtures. Fracture mechanics in terms of critical stress intensity factor and fracture toughness have been employed to study the consolidation behaviour for mixtures of PEGs and microcrystalline cellulose powder. It was found that the measured values are lower than those predicted by simple addition. However, the same brittleness trend exhibited by the individual PEGs was found to apply to the mixtures with MCC.

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