Application Note

Indentation Testing

of Aspirin Tablets

Experimental

The NanoTest system fitted with the MicroTest high load head was employed to investigate the continuous Depth vs. Load response of three aspirin tablets produced by different manufacturers.

The samples were attached to a specimen stub by means of a rapid-setting adhesive. Since the samples were curved, the MicroTest 2-dimensional automatic levelling stage was used to ensure that the indented surface was normal to the diamond axis. The levelling procedure relies on the coordinates of contact points rather than on continuous scanning, and can therefore be carried out with the indentation diamond itself.

micro-hardness testing of pharmaceutical tablets

Results

The Depth vs. Load curves shown were obtained as the applied load was increased and then decreased back to zero. The hardness of the material is determined from the final, permanent deformation. Clearly, tablet C was significantly harder than tablets A and B. In addition, the steps in the loading curve of tablet C indicate brittle fracturing behaviour and the possibility of damage during packaging, handling and transportation.