Relationships between the effective interparticulate contact area and the tensile strength of tablets of amorphous and crystalline lactose of varying particle size.

The aim of this study was to experimentally evaluate an equation for describing tablet tensile strength by studying relationships between the measured tensile strength and the calculated effective interparticulate contact area in tablets prepared from varying size fractions of amorphous and crystalline lactose at varying pressures. Amorphous lactose produced tablets of higher tensile strength than crystalline lactose and there was a tendency for reduced particle size to increase tablet strength. The tablet tensile strength correlated reasonably well with the effective area of contact for each material after compensation for a particle size-related intercept. It was thus concluded that the tensile strength equation under investigation reflects a structural property of the tablet which correlates with the tensile strength of the tablet. The slope of the tensile strength-contact area relationship differed between the materials and original particle size also had a small effect on this parameter. The results indicate thus also that the differences in compactability between amorphous and crystalline lactose are mainly the result of differences in bonding capacity, although differences in particle deformability also play a limited part.