Physicochemical properties and surface free energy of ground talc

When the talc was ground with the vibrating mill, a remarkable decrease in crystallinity was observed. Especially, the decrease of peak intensities at (002), (004) and (006) plane was detected. The decrease of mean particle size (D50) and the increase of specific surface area were also observed as the increase of grinding times. The heat of immersion was significantly increased as the increase of grinding times. The surface free energy of talc was measured by the liquid penetration rate measurement. The polar part of surface free energy (γp) was considerably increased after 10 min of grinding (γp: intact talc 4.7→10 min ground talc 12.1 mN/m). The change in the polarity (γp/(γp+γd)) was also observed by the grinding. The polarity of intact talc was 26%. The polarity was increased to 41% by 10 min of grinding of talc. The disintegration time and the dissolution rate of ethenzamide formulated with ground talc were remarkably faster than those with intact talc. It seemed that more hydrophilic surface might be appeared by the grinding of talc. By using the ground talc as a lubricant, it might be possible to control the disintegration rate and the dissolution time of drug from tablet.