Destructive Testing
Does Your Hard Tablet Measure Up?
Vitamins and medicines oftentimes come in the form of hard tablets. Manufacturers need to ensure that they hold
together from time of manufacture to moment of consumption by the customer. R&D scientists have come up with
a battery of tests that can evaluate the physical properties of tablets related to fracturability and crush worthiness.
Instruments of choice called “Texture Analyzers” which have come initially from the food industry are being used to
perform these tests. Figure 1 shows an example of this type of instrument.
Figure 1: Brookfield
CT3 Texture Analyzer
Figure 2a: Probe make
contact
Figure 2b: Tablet after crushing action
Compression and tension tests are the two modes of operation afforded by Texture Analyzers. They can compress a test
sample, penetrate the sample with a probe, or pull the test sample apart. Simulating the actions of squeezing, biting,
and stretching are typical types of tests run with Texture Analyzers. There are many different probes to choose from. The
travel speed of the probe is defined as part of the test method.
Tablet chewability is another piece of information that pharmaceutical companies would like to know. The Texture
Analyzer is appropriate for this type of testing as well. This article gives a brief summary of the test methods and
the data that can be used to qualify acceptability of hard tablets for
their integrity and chewability. Quality Control departments are the
practitioners of these test methods in everyday tablet production.
CRUSH TEST
Using a Texture Analyzer with load cell rated at 50kg, a cylindrical probe
with flat bottom known as TA-AACC36 comes down onto the tablet
standing on its rounded edge, makes contact, and travels a distance of
4mm at a rate of 1mm/sec. Figure 2a shows the tablet when the probe
first makes contact. Figure 2b shows the condition of the tablet after the
probe has performed the crushing action. Cracks across the surface of
the tablet are visible.
Figure 3 shows that the peak load applied to the tablet by the cylinder
probe is 6800 grams. This maximum force is a measure of sample
firmness/hardness and equates with the force required to initiate
Figure 3: Force load in grams vs. time for the
crush test on the round tablet
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TEXTURE ANALYZERS
POWDER FLOW TESTERS
T: 800.628.8139 / 508.946.6200
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fracture in the tablet, either when hitting against other tablets or when placed between the molar teeth in your mouth.
When the same data is plotted on a graph that shows load vs. penetration distance, the area under the curve from the
start of the test to the peak load is a measure of work done, i.e. the energy required to break the sample by the molars.
Texture Analyzers will automatically compute this value, in this case 32.2 mJ. When using software with the Texture
Analyzer, the information will be organized as shown in the following table.
Sample
Hard Round Tablet
Hardness
6800 gm
Hardness Work Done
32.20 mJ
FRACTURE TEST
The fracture test is accomplished by driving a small hemispherical ball probe into the flat surface of a solid tablet as
shown in Figure 4a. A deformation distance of not more than 60% of the sample height is usually enough for the ball
probe to fracture the tablet as shown in Figure 4b. As the probe starts to penetrate the tablet, the measured force
climbs quickly to a peak load value as shown in Figure 5. At this instant initial fracture of the tablet takes place. Then as
the probe continues to the defined depth, smaller fractures occur. The force required to fracture the tablet is useful for
determining the mechanical properties of new formulations such as the modulus and tensile strength.
Figure 4a: Probe approaching Figure 4b: Tablet after fracture Figure 5: Graph of force load vs. time as
tablet
probe penetrates tablet
BENDING TEST
The Three Point Bend fixture is used to test the snap-strength of the tablet. Figure 6 shows the test set up used to
position the tablet on two supports while a blade-shaped probe comes down to make contact. Once the probe makes
contact, the tablet bends very slightly if at all until it fractures in two. Figure 7 shows the graph for this behavior.
Figure 6: Alignment of probe & sample Figure 7: Graph of force load vs. time for the bending test on the hard capsule sample.
ISO 9001 CERTIFIED
VISCOMETERS
RHEOMETERS
TEXTURE ANALYZERS
POWDER FLOW TESTERS
T: 800.628.8139 / 508.946.6200
www.brookfieldengineering.com
The peak load is the maximum force recorded before the tablet snaps in two. This is a measure of sample hardness/
firmness; for this particular tablet it is around 26,000 grams. The area under the graph from the start of the test to when
the tablet snaps in two is a measure of work done. This value correlates with the amount of energy required to bend and
break the tablet.
The work done to snap the tablet was 65 mJ and the Texture Analyzer automatically calculates this value.
CONCLUSION
These three tests are good examples of the physical characterization work that R&D can now perform on tablets before
introducing them into manufacturing. Quality Control will perform similar tests on random samples to verify that
performance criteria are being upheld.
Authors: Eric Chiang, Product Manager, Texture Analyzers Email: e_chiang@brookfieldengineering.com
Stephanie Shepard, (Summer Intern) Lab Assistant, Texture Analyzers
Robert G. McGregor, General Manager, Global Marketing Email: r_mcgregor@brookfieldengineering.com
Brookfield Engineering Laboratories, Inc., 11 Commerce Blvd., Middleboro, MA 02346
Tel: 1.508.946.6200
Fax: 1.508.946.6262
Website: http://www.brookfieldengineering.com
ISO 9001 CERTIFIED
VISCOMETERS
RHEOMETERS
TEXTURE ANALYZERS
POWDER FLOW TESTERS
T: 800.628.8139 / 508.946.6200
www.brookfieldengineering.com