[learn_more caption=” Sonia M. Razavi, Alberto Cuitiño”] Sonia M. Razavi,

Alberto Cuitiño[/learn_more]

Abstract:

Ultrasound testing has been recently introduced as a non-destructive method to measure tablet strength. This requires the measurement of the time of flight of an acoustic wave pulse traveling through the specimen from the transmitting transducer to the receiving one. Young’s modulus can be extracted by measuring the speed of sound of the transmitted ultrasound signal for a known sample size. We can then relate the Young’s modulus with the mechanical strength of the compacted granular solids, which is usually tested by destructive methods such as diametrical compression test. These destructive tests not only damage the structure of a tablet and cause loss of product, but also provide limited information about the mechanical state of a tablet and cannot be included in an on-line process.

In this study, cylindrical tablets were prepared in two ways: batch and continuous. The formulation was kept constant (90% lactose monohydrate, 9% acetaminophen, and 1% magnesium stearate), while the compaction force and level of shear strain varied. Young’s modulus and tensile strength were measured using ultrasound testing and hardness tester, respectively. It was observed that, as the blend was exposed to an increasing level of shear strain, the speed of sound values decreased and the tablets became both softer and mechanically weaker. We also noticed that in order to predict the hardness of a tablet, we need to take two properties into account: Young’s modulus and relative density of that tablet. Ultrasound testing was found to be very sensitive in differentiating tablets with similar formulation but produced under different processing conditions, thus, providing a fast, and non-destructive method to be placed on/at-line after tablet production for hardness prediction.