A RELATIONSHIP BETWEEN SURFACE FREE-ENERGY AND POLARITY DATA AND SOMEPHYSICAL-PROPERTIES OF SPHEROIDS

Spherical particles have been produced by extrusion and spheronisation of a wet mass of lactose, microcrystalline cellulose and indomethacin (as a model drug), and of mixtures of microcrystalline cellulose, bar ium sulphate and glyceryl monostearate (to test the general applicabil ity of the surface energy predictions). The surface energies of the po wders were estimated from contact angle measurements. The work of cohe sion of each powder, and the work of adhesion between pairs of powders were assessed, as were spreading coefficients of the powders over eac h other. It was found that the spheres produced without indomethacin ( lactose and microcrystalline cellulose only) required a significantly higher force to cause crushing, and were also of higher density than a ny of the four batches which contained different levels of indomethaci n. The batches with added indomethacin had similar physical properties irrespective of indomethacin loading. Spheroids containing glyceryl m onostearate and barium sulphate had much higher porosities and lower c rushing strengths than the indomethacin based formulations. These diff erences are explained in terms of much lower works of adhesion and coh esion for barium sulphate and glyceryl monostearate than were obtained for the other materials. The differences in the properties of the sph eroids have been explained in terms of interfacial phenomena, and in p articular the relative works of adhesion between the solids.