Biomedical subjects
Publications and source records attributed to S Malamataris.
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The tensile strength of tablets made from phenobarbitone and sodium phenobarbitone formulations after storage at increasing ambient relative humidity has been investigated. The moisture sorption and desorption profiles of the formulations were analysed for three locations of moisture: monolayer adsorbed moisture, normally condensed moisture and absorbed moisture. Maxima in tensile strength occur at moisture distributions determined by the disintegrant used. The changes in tensile strength have been explained in terms of changes produced in the interparticle separation, the range of the interparticle forces and changes in the ratio of the binding to diffusional forces, acting on the water molecules which are on the particles' surface.
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The plasto-elasticity of mixtures of paracetamol and Avicel powders and the tensile strengths of their tablets varied with the sizes of the particles and with the compositions of the mixtures. Tests made on these and other tablets showed that the logarithms of their strengths were inversely proportional to the ratios of the samples' elastic recovery: plastic compression; they exhibited lamination or capping when this ratio was greater than 9.
A study has been made of the tensile strength and compression during tableting of lactose, sodium chloride and calcium phosphate powders after they had been coated with small amounts of stearic acid, polyethylene glycols and polyvinylpyrrolidones. The properties of the systems were measured over a range of temperatures. The tensile strength and the compression behaviour depended not only on the amount and type of the coating material but also on the homologous temperature of processing. The changes in tensile strength have been explained in terms of changes in interparticle separation, changes in interparticle forces and the formation of welded bonds by the coatings. The compression results have been analysed in terms of the Heckel and the Cooper & Eaton equations.
The effects of using different grades of PVP and gelatin binders on three sieve fractions of lactose granulated in a fluidized bed granulator and tablets have been studied. Increasing the molecular mass of PVP or bloom number of gelatin resulted in a decrease in granule friability but in an increase in their average size and porosity and in the tensile strengths of the resulting tablets when compressed to a fixed apparent density. The results have been explained in terms of the effects of moist and dry binder bridges on bonding of particles in granules and tablets.