Compactibility of ternary mixtures of pharmaceutical powders

The tablet hardness (D) of tablets made of mixtures of microcrystalline cellulose (CM), dicalcium phosphate dihydrate (FC) and sodium lauryl sulfate (LSS) and formed under a compaction pressure (P_c) ranging up to 980 MPa has been determined. The compactibility of different mixtures (55) was defined with the maximal tablet hardness reached (D_max) and the slope (n) and intercept (I) of the regression curve, using the equation: ln(-ln(1 - D D_max)) = n ln P_c + I. The experimental maximal tablet hardness of 11 different proportions of the components of a binary mixture of CM and FC showed a maximum at about 80% of CM. Addition of increasing proportions of LSS caused a decrease of tablet hardness and a decrease in the position of this maximum; the experimental data of D_max for the CM-FC mixtures, with 2% LSS, showed a maximum at about 50% of CM. The tablet hardness of the mixtures was also dependent on compaction pressure. At high compaction pressures the tablet hardness showed more clearly the characteristics of bonds between particles of different materials, whereas at low compaction pressures it seems to represent just an average of bonds between particles of the same materials.