The effect of crystal hardness on radial pressure at the wall of a tabletting die

The force transmitted to the die wall during the tabletting of seven crystalline pharmaceutical materials has been measured using a photoelastic technique. The Vickers hardness of these materials has also been measured. The compounds examined were aspirin, urea, hexamine, salicylamide, potassium chloride, sodium chloride and sucrose. The pressure on the die wall increases as the hardness value decreases. The Vickers hardness of the resultant tablets was also measured; aspirin and sodium chloride both showed the occurrence of work hardening in that the tablets had a greater hardness value than the parent crystalline substance.