Utjecaj veličine čestica na svojstva tečenja granulata

In pharmaceutical industry the majority of ingredients is in the form of powder with different particle size, shape and density. These characteristics influence packing geometry, porosity, homogeneity, bulk density and segregation of the mixture determining rheology of the powders. Rheological properties are crucial for majority of processes in the production of solid dosage forms. The size of the particles influences the flowability through the impact on the adhesive and cohesive forces, but also influences chemical and physical characteristics of medicinal product. The mixtures of powders prepared by different methods contain particles of different sizes, particle size distribution, shape, surface texture, porosity and electrostatic charge and therefore they show different behaviour. The aim of this study was to determine the influence of particle size on flowability of the samples which have been prepared by different methods of granulation. For that purpose, the particle size distribution has been determined by the sieve method and the flowability has been examined by determining compressibility index, Hausner ratio, the angle of the repose and the flow rate through an orifice. The process of granulation has resulted in the increase of the particle size and improvement of the flow characteristics of the powder sample. Particle size distribution, shape and surface texture of the prepared granules greatly depended on the method used (wet vs. dry granulation). Granulates prepared by wet method (conventional procedure and fluid-bed granulation) have been characterised as having bigger surface-volume diameter (0.136 mm and 0.131 mm), more narrow particle size distribution (geometric standard deviation 1.679 and 2.089) as well as improved flowability (compressibility index 9.93±0,65 % and 12.68±0.96 %; Hausner ratio 1.110±0. 020 and 1.145±0. O 13; flow rate through an orifice 200 ml/(21.4±0.2) s and 200 ml/(15.1±0.4) s) in comparison with the granulate prepared by dry granulation method (surface-volume diameter 0.099 mm; geometric standard deviation 2,800; compressibility index 16.85± 0.83; Hausner ratio 1.203±0.012; flow rate through an orifice 200 mi!/ (29.4±0.3) s). Combining different methods in determining characteristics of the flowability has allowed evaluation of different aspects of the powder flowability