Tablet adhesion often appears unexpectedly at a late stage and can be difficult to solve.
Sticking & Picking
Sticking and picking is a common problem during tablet development and manufacture. It occurs when particles of the tablet formulation adhere to the punch face. Using an adhesion punch specifically designed for this application, the risk of sticking of new formulations or to troubleshoot solutions for existing products can be quantified.
Sticking is not specific to the tooling’s embossing as it can occur on any area of the tooling face, whereas picking is generally related to tooling’s embossing and occurs mostly within the logo and island areas.
Picking usually occurs within the “closed” numbers and letters, these numbers are 0,4,6,8, and 9, some of the letters are A, B, D, and e.
Adhesion Force Measurement
Merlin offers the capability of measuring punch sticking using our adhesion punch by mimicking the real conditions to measure production relevant sticking. This testing involves compressing compacts of the material at selected forces and compressing enough compacts for the sticking signal to stabilise. This can be usually be achieved with 5-20 compacts per point. Sticking varies with punch force and therefore it is useful to assess at least 3 forces in the range of interest.
Measuring adhesion force alone does not indicate picking risk as it is a measure of interaction between the upper punch and the tablet surface. Therefore, there are 2 important risk factors: Adhesion between punch face and compact and the cohesion of the compact.
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