Internal friction of compressed pharmaceutical powders observed in terms of the die wall pressure.

@article{Fukuda1980InternalFO,
  title={Internal friction of compressed pharmaceutical powders observed in terms of the die wall pressure.},
  author={Tomoaki Fukuda and Yoshinobu Fukumori and Shinji Wada and Y Hanyu},
  journal={Chemical \& pharmaceutical bulletin},
  year={1980},
  volume={28 2},
  pages={
          393-40
        }
}
The internal friction of powders was examined during tablet preparation for lactose and phenacetin as base materials and for potassium chloride, potassium bromide and sodium chloride as model samples. The coefficient of internal friction decreased with the porosity, even if the voids were filled by fragmentation of particles or by plastic flow. When the porosity had reached zero, the state of the whole bed of powder was found to be plastic, where the coefficient of internal friction was zero… 
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