ABSTRACT
According to the commonly used tablet compressibility, compactability and tabletability equation, the influence of pressure range on the fitting results and parameters of different compression equations was studied, and the optimal pressure range of different equations was determined. Plastic material microcrystalline cellulose (MCC) PH102, brittle material spray dried lactose and Chinese medicine Sanqi were used as experimental objects, the compression curves of tablets were obtained by the combination of dies with different diameters. For Heckel equation, the shape of Heckel section of different materials is not uniform, and the specified linear fitting range cannot be obtained, therefore, different distances between fitting pressure starting point and starting point were set to observe the influence of pressure range on R2 of Heckel equation. The Kawakita equation, Gurnham equation, Ryshkewitch-Duckworth (R-D) equation and Power equation are fitted in three different pressure ranges of 15-200, 15-300 and 15-400 MPa, respectively. In order to find the best linear region of Heckel equation, the 3D scatter diagram of "starting point of pressure, pressure range and R2" is drawn. The best linear pressure ranges of Heckel curves of MCC, lactose and Sanqi were 20-170, 20-220 and 10-90 MPa, respectively. It is proved that the 3D scatter diagram is an effective method to find the linear range of Heckel equation. The change of pressure range has little influence on the curve fitting effect and compression parameters of Kawakita equation, Gurnham equation and Ryshkewitch-Duckworth equation. The low pressure range of 15-200 MPa can meet the fitting requirements of Kawakita equation, Gurnham equation, R-D equation and Power equation for different materials. Therefore, only by optimizing the pressure range, can the good fitting effect be ensured and the obtained compression parameters be more reliable and interpretable.