Effect of the lubricant magnesium stearate on changes of specific surface area of directly compressible powders under compression

During compression, powders fragment, plastically deform, and/or may behave both ways. Different profiles of specific surface area changes have been shown in several studies for many powders. In this study, the effect of a lubricant on the specific surface area of a powder was studied during the consolidation process of the powder as an attempt to clarify the behavior of powders under compression. Changes in specific surface areas of Starch (Rice starch), cellulose (Avicel^® PH102), spray dried lactose (Zeparox^®), and dibasic calcium phosphate (Emcompress^®) were studied using gas adsorption technique. Magnesium stearate was used as a lubricant. Specific surface area of plastically deforming materials; cellulose, and starch was clearly affected by the addition of lubricants. Spray dried lactose combined both fragmenting and plastically deforming behavior in its consolidation under compression and its specific surface area was slightly affected by the addition of lubricant. Specific surface area of fragmenting material; Dibasic calcium phosphate was not affected by the addition of a lubricant.