Journal of Scientific & Industrial Research Vol. 73, January 2014, pp. 51-56 Rearrangement of particle and compactibility, tabletability and compressibility of pharmaceutical powder: A rational approach Subrata Mallick Department of Pharmaceutics, School of Pharmaceutical Sciences, Siksha O Anusandhan University, Kalinganagar, Bhubaneswar-751003, Orissa, India Received 20 July 2012; revised 17 May 2013; accepted 23 August 2013 Characterization of the entire densification process is really difficult by using one simple monovariate equation to be successfully applied in research and development of tablet formulation. Particle rearrangement process can be divided into two steps and described by biexponential Heckel equation. By non-linear approach quantification of compactibility, compressibility and tabletability of the pharmaceutical powders is possible which is supposed to be more accurate compared to least square methods after log transformation of the data. The knowledge of relationship of tableting properties can be utilized for designing formulation and scale-up. Keywords: Compaction process, Tabletability, Compactibility, Compressibility, Heckel equation, Particle rearrangement. Introduction It is really difficult to use one simple monovariate equation to cover the entire densification process 1 to be successfully applied in research and development of tablet formulation. Walker 2 developed the earliest model in 1923, whose analysis is based on the reduction in volume of the powder bed as a function of the logarithm of the applied compression pressure P (Table 1). Where, V is the relative volume, and w, the Walker coefficient and A is a constant. In this work, w values were found to be greater for plastically deforming materials when compared to those for brittle fractured ones. Sønnergaard 3 modified Walker model where, V' is the specific volume and w' the Walker constant as compressibility parameter expressing the volume reduction corresponding to one decade in the pressure P. V sp is the specific volume at the pressure 1MP a . Further, he quantified the compactibility by using a linear relationship between the diametral compressive strength of tablets and the applied pressure. Where, mechanical strength of the tablets is the crushing force normalized with the dimension of the tablet and termed the specific crushing strength, SCS. C p is the estimated slope of the regression line as dimensionless compactibility parameter. Sønnergaard then established a relationship between the compactibility parameter C p and the compressibility parameter w . Least square methods have been utilized for estimation of parameters. Tabletability has been described by a plot of tensile strength versus compaction pressure 4 . Heckel 5,6 characterized the powder compaction phenomenon using the equation (Table 1) where, D is the relative density of a powder column being compacted at the pressure P. The parameter A is related to low pressure densification by particle rearrangements obtained from intercept of the plot —————— Author for correspondence E-mail: profsmallick@gmail.com Table 1— Summary of models for characterization of tableting properties Model References V = -w.logP + A w = Walker coefficient or, compressibility coefficient Walker 2 V' = -w'.logP + V sp w' = Compressibility constant Sønnergaard 3 SCS = Cp*P + b C p = Compactibility parameter Sønnergaard 3 Ln1/(1-D) = KP + A K = Plasticity Heckel 5,6 P/C = P/a + 1/ab N/C = N/a + 1/ab a = Compactibility constant, 1/b = Cohesiveness Kawakita & Ludde 7 T s = T o .exp(-kε) k = Compactibility coefficient Ryshkewitch 41,42 T s = C + k'P k' = Tabletibility coefficient Sun et al. 4 ; Joiris et al. 43