Tablet Crush Resistance and Break Strength
Many products come in tablet form, with a durability designed for both packaging and for use. Too brittle or too hard, and they may not be fit for use, or at best perform below expectation. The only way to determine consistency is mechanical testing of samples.
As a quality control measure on the production line, or as a manufacturing design tool, computer-controlled mechanical testing, based on criteria determined for an acceptable range of measures, is the only reliable method.
So what does it take to crush or break a tablet product?
In this test, an FTC TMS-Pro Texture Analyzer was fitted with a 500 N intelligent loadcell and 1.5 inch (38 mm) cylinder probe. A short program advanced the probe to touch the tablet sample before advancing a further 1 mm, as sufficient to always break the sample. The TL-Pro control software also allows for break detection to stop the probe advancing further than necessary. The probe then returned automatically to the starting position.
The graphical representation from TL-Pro, of the test results for the four samples, is shown here (force applied, against cumulative displacement).
The critical factor is the initial fracture point of the tablet sample. This trace also profiles resistance from the fragments as the probe continued to crush downwards.
The same results with additional calculations are shown here.
- Average = arithmetic mean
- SD = standard deviation
- CV = coefficient of variation: (SD/Mean) x 100
The break point of many tablet products is a balance between resilience to the point of use, and viability in use. Frequently the tablet size denotes a required dosage, whether it is a vitamin or a dishwasher additive, and nobody wants either a quarter mint in the bottom of a packet or a whole one that is too hard to crack. Other factors are important, including the pattern of breaking, but the crush strength is a primary indicator of manufactured quality. Mechanized testing as shown here is reliable and repeatable. The method allows for any minor size variations, and provides a clear profile of the initial break. Careful initial testing of a product can produce upper and lower tolerance levels for the required break force, and be used for quality monitoring on the production line, producing instant pass and fail indication. Any drift towards failure can be fed back to the line, saving time and cost.