Compression characteristics of granulated materials. III. The relationship between air permeability and mechanical strength of tablets of some lactose granulations

Abstract

Lactose was granulated with 5% by weight polyvinylpyrrolidone as binder by a wet massing-screening procedure. 14 granulations were produced by varying the amount and type of solvent for the binder during the wet massing. The size fraction 500–710 μm was prepared for each granulation and tablets were compacted in an instrumented single-punch press at 150 MPa. The tablets were then stored for 2 days at 40% relative humidity and the tensile strength was measured. Generally, the tablet strength increased with increased amount of agglomeration liquid except for the lowest amount of liquid which showed a somewhat higher tablet strength than expected from the general trend. It is suggested that this is primarily due to an increased amount of binder in these granulations. The type of binder solvent also affected the tablet strength but to a smaller extent. The air permeability compaction-pressure profiles for these granulations have been studied earlier and were here compared with the tablet strength data. Generally, the changes in tablet strength were related to variations in the degree of granule fragmentation in the different granulations. The results therefore indicate that the degree of fragmentation of the granules during compression is of significant importance for the tablet strength.