STUDIES ON INTERNAL STRUCTURE OF TABLETS .6. STRESS DISPERSION IN TABLETS BY EXCIPIENTS

The aim of this study was to reduce the stress concentration of a medi cine by dispersing the stress in tablets at tableting by addition of e xcipients. The mechanism of the stress dispersion was elucidated. Phen acetin (PHE) was used as a model of crystalline medicine with a high b rittleness, and the degree of stress dispersion was evaluated by the c hange in the exposed surface area of PHE. To learn the mechanical stre ngth of tablets, the crushing strength and friability were measured, t heir internal structure was analyzed by the porosity and pore size dis tribution, and stress relaxation experiments were performed. The resul ts were as follows. Calcium silicate (Florite(R) RE, FLR) showed a hig h stress dispersion effect, adding a high formability and mechanical s trength to tablets. It was thought that the high stress dispersion res ulted from the rapid stress relaxation caused by the plastic deformati on and brittleness fracture of pores in FLR under a low compression pr essure. Thus the stress caused locally on PHE particles may disperse.