Maximum upper punch pressure at each load with a dwelling time of 60 s was recorded for compaction of each tablet in the laboratory ambient condition (∼27 °C, ∼60% RH). The thickness of each pellet was measured with a digital micrometer (Mitutoyo, Japan). This data was used for the calculation of apparent density, porosity and degree of volume reduction. Tablets were preserved in a wide mouth tightly closed container immediately after compression. Cooper and Eaton developed a biexponential

equation for describing the compaction of powders as a function of applied pressure and adopted from other fields of industry for research in pharmaceutical compression process. The equation is equation(1) ((1/D0)−(1/D))/((1/D0)−1)=aexp(−Ka/P)+bexp(−Kb/P)where selleckchem DNA Damage inhibitor D0 and D are the relative density at zero pressure and at pressure P, respectively, a indicates the fraction of the theoretical maximal densification, which could be achieved in the first stage by filling large voids by interparticulate slippage and

b indicates small voids by deformation or fragmentation at a higher pressure in the second stage of densification. Ka and Kb describe the magnitude of pressure at which the respective compaction process would occur with the greatest probability of density. Tablets were produced on a hydraulic pellet press and the parameters of the second stage due to particle deformation were determined from the graphical plot of Ln((1/D0)−(1/D))/(1/D0)−1 versus 1/P, where the slope of the linear region is Kb and the ordinate intercept of that linear region of the second stage compaction measures (a+b). Rearrangement of discrete particles could be mafosfamide described by two major steps [24] and [25] based on cohesiveness of the powdered material as (i) primary rearrangements of fine discrete particles and (ii) secondary rearrangements. Replacing pressure, P, by the tapping number, N, in the

Cooper–Eaton equation we get equation(2) ((1/D0)−(1/D))/((1/D0)−1)=a1exp(−K1/N)+a2exp(−K2/N)where D0 and D are the relative density before tapping obtained by poured density divided by equilibrium tapped density and the relative density at Nth tapped obtained by apparent density of a powder column divided by equilibrium tapped density, respectively. The coefficient K1 represents the tapping required to induce densification by primary particle rearrangements, which has the greatest probability of density, whereas K2 represents the tapping required to induce densification through secondary particle rearrangements. a1 and a2 are the dimensionless constants that indicate the fraction of the theoretical maximum densification of tapping, which could be achieved by filling voids by primary rearrangements (a1) and secondary rearrangements (a2).