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Strain Rate Sensitivity (SRS) measures the change in yield pressure between slow compression speed and production speed.
SRS is a measurement taken from the Heckel test. By comparing the yield pressures at fast and slow compression speeds, we can assess the amount of elasticity present in the material, the higher the elasticity the greater the issues for tabletting.
SRS gives an indication of the risk of scale-up on the material characterisation of Active Pharmaceutical Ingredients. Categorising the API according to yield pressure (Slow) and SRS allows the API to be compared against the properties of other materials.
For some materials, the deformation characteristics change with rate of applied force. This can be estimated by calculating the SRS.
The yield pressure calculated during the Heckel tests at high-speed compression is compared to that at slow speed using the equation:
%SRS = (Py Fast - Py Slow / Py Slow) x 100
We can complete a Heckel test on your test materials to calculate the Strain Rate Sensitivity. During a Heckel test the test material is compressed under high forces using a compaction simulator. Force verses relative density measurements are used to determine the theoretical yield pressure of the material using the Heckel equation, the SRS can then be calculated.
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