STUDIES ON DIRECT COMPRESSION OF TABLETS 23 THE IMPORTANCE OF SURFACE-ROUGHNESS FOR THE COMPACTIBILITY OF SOME DIRECTLY COMPRESSIBLE MATERIALS WITH DIFFERENT BONDING AND VOLUME REDUCTION PROPERTIES

The axial tensile strength of double layer compacts prepared from a precompressed layer with varying surface roughness and a layer of material in powdered form, has been investigated for sodium chloride, Avicel ® PH 101, Sta-Rx ® 1500, latose, sucrose and Emcompress ®. The materials consolidating mainly by plastic deformation were all very sensitive to a decrease in the surface roughness of the pecompressed layer of the double-layer tablet. Presumably the plasticity of these materials is insufficient to produce high surface areas for bonding between the two layers. The fragmenting materials, lactose, sucrose and Emcompress ®, were relatively unaffected by the pretreatment of the first layer. This suggests that the surface area utilized for bonding by the fragmenting materials is large. For these materials a high bonding surface area between the particles in the tablet seems to be the primary requisite for a high tablet strength. The compact strength of the investigated materials is primarily dependent on intermolecular forces. © 1990.