Analysis of the compression mechanics of pharmaceutical agglomerates of different porosity and composition using the Adams and Kawakita equations

Purpose. To analyze the mechanics of some pharmaceutical agglomerates durin g uniaxial confined compression by using compression parameters derived fro m the Heckel, Kawakita and Adams equations, and to study the influence of t hese compression parameters on the tablet-forming ability of agglomerates. Methods. Force and displacement data sampled during in-die compression of a gglomerates was used to calculate compression parameters according to the H eckel (sigma(y)), Kawakita (1/b and a), and Adams (tau(0)') equations. Mech anical strength of single agglomerates as well as the air permeability and tensile strength of tablets prepared from them were also determined. Results. sigma(y) from the Heckel equation did not differ between agglomera tes of different porosity. Both 1/b and tau(0)' varied with agglomerate por osity and composition. These two compression parameters were linearly relat ed to each other. No general correlation was found between 1/b and tau(0)' and the strength of single agglomerates. The two parameters were related to the intergranular pore structure and tensile strength of tablets formed fr om the agglomerates. Conclusions. 1/b and tau(0)' may be interpreted as measures of the agglomer ate shear strength during uniaxial confined compression, and as such they m ay be used as indicators of the tabletting performance of the agglomerates.