An Attempt at Bringing to Light a “Phase Inversion” in a Binary Mixture of Two Dimensional Rounded Particles

Abstract

It has been demonstrated previously in our Laboratory that the disintegrant concentration corresponding to an interparticular network between drug or diluent particles in tablets may be calculated.

When the disintegrant concentration increases little by little, for a critical concentration, a sudden modification of the physical properties of the powder mixture and of the resulting tablets can be observed.

A new structure is set up in the tablet: in a way, a “phase inversion” is produced.

This experimental critical concentration is the same as the calculated critical concentration for more or less rounded particles.

An investigation into the physical properties of binary powder mixtures and of resulting tablets is carried out when increasing, little by little, the quantity of disintegrant particles: Starches and their derivatives, cross linked PVP, are more particularly studied.

The authors study:

• – The flowing properties of powder mixtures

• – The compressibility (Hardness/Compression forces, transmission forces through the powder mixture during compression, compression cycles…)

• – The physical properties of tablets (hardness, structure hydrophilicity, disintegration time and drug dissolution).

Several formulations were studied. The results point out the setting up of the continuous network of the small particles between the larger particles for the calculated critical concentration. The same theory may be applied to the hydrophilization of powders in hard gelatin capsules and to all the more o r less rounded two dimensional particles in a mixture.