Compactability Study - Heckel Plot

In 1961 Heckel postulated a linear relationship between the relative porosity (inverse density) of a powder and the applied pressure. The slope of the linear regression is the Heckel constant, a material dependent parameter inversely proportional to the mean yield pressure (the minimum pressure required to cause deformation of the material undergoing compression). Large values of the Heckel constant indicate susceptibility to plastic deformation at low pressures, when the tablet strength depends on the particle size of the original powder. The intercept of the line indicates the degree of densification by particle rearrangement.