Working with Heckel plots: method for checking the plausibility of force displacement data
Nov. 1, 2010, midnight
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To analyze the powder compression behavior and deformation mechanisms of materials, the Heckel Plot is commonly employed. This plot illustrates the volume reduction of a powder bed during compression by plotting ln(1/e) against pressure. The sections of the Heckel Plot related to the loading phase provide insights into the powder's deformation behavior. The slope's value is highly sensitive to minor errors in the independent density determination, primarily arising from inaccuracies in displacement transducers, reference positions, punch tilting, etc., during tablet compression. To minimize these errors, a precise external height-measurement system was implemented at the compaction simulator Stylcam 200R.
For the characterization of powder under conditions resembling production settings, the Stylcam 200R was selected due to its capacity to simulate tabletting speeds similar to those found on various production tablet presses. Additionally, it was equipped with a pair of concave punches, offering the advantage of early detection of capping and laminating issues during development. Given the significant dependence of Heckel Plots on measurement accuracy, a plausibility check for the acquired data was developed.