D. Khossravi et Wt. Morehead, CONSOLIDATION MECHANISMS OF PHARMACEUTICAL SOLIDS - A MULTI-COMPRESSION CYCLE APPROACH, Pharmaceutical research, 14(8), 1997, pp. 1039-1045
Purpose. The consolidation behavior of various pharmaceutical solids w
ere characterized using compression-cycle profiles. Compression-cycle
profiles for both uncompacted powder and formed tablets were obtained.
These profiles were used to qualitatively and quantitatively characte
rize the consolidation mechanism of pharmaceutical solids. Methods. An
Instron Universal Testing apparatus and a specially instrumented die
coupled with a computerized data acquisition system were utilized to m
easure the upper-punch pressure and the corresponding die-wall pressur
e during the compression cycle. Results. Compression cycle profiles we
re obtained for a variety of pharmaceutical materials. Based on these
profiles, parameters such as hysteresis areas, loading slopes, and unl
oading slopes were calculated for the materials studied.Conclusions. M
aterials that consolidate by plastic deformation have similar compress
ion cycle profiles for the first and subsequent compression cycles ind
icating that the plastic deformation process occurs to the same extent
on the first as well as subsequent compression cycles. For brittle ma
terials, the brittle fracture process occurs during the first compress
ion cycle. During subsequent cycles the tabletted material does not un
dergo further yield or failure and primarily undergoes elastic deforma
tion. Low molecular-weight polyethylene glycol is an excellent model m
aterial for plastically deforming materials, whereas sucrose or sodium
citrate are excellent examples of materials that consolidate by britt
le fracture.