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Brookfield AMETEK

Pharmaceutical Films

Test Principle

Evaluation of the film burst strength of two different pharmaceutical films using a 3 mm cylinder probe.

Background

The strength of a film material can be quantified using the CT3 Texture Analyser by a penetration test using a 3 mm cylinder probe to determine the strength (rupture point) of the film material. A force is applied to the sample to deform the sample to rupture point. This is a common method also used to measure points of weakness in a film or seal during manufacturing, simulating circumstances whereby the material may burst during packaging and transport.

The CT3 Texture Analyser can also quantify the elasticity of the film by measuring the deformation at hardness.

Method

Equipment

  • CT3 with 4.5 kg load cell
  • Fixture Base Table (TA-BT-KIT)
  • TA 42 (3 mm Cylinder Probe)
  • TA-FSF Film Support Fixture
  • Texture Pro CT Software

Settings

  • Test Type: Compression
  • Pre-Test Speed:°.5 mm/s
  • Test Speed: 1.0 mm/s
  • Post-Test Speed: 1.0 mm/s
  • Target Type: Distance
  • Target Value: 8.0 mm
  • Trigger Force: 5.0 g

Note: The hardness values will increase relative to the increased penetration depth. Consequently, for comparison purposes, penetration distances must always be reported.

It is recommended that the pre-test speed be the same as or less than the test speed for accurate trigger detection; for example, 1.0 mm/s test speed will require ≤ 1.0 mm/s pre-test speed.

Procedure

  1. Attach the cylinder probe onto the CT3.
  2. Place the fixture base table on the base of the instrument and loosely tighten the base screws to enable some degree of mobility for the alignment stage.
  3. Place the TA-FSF Film Support Fixture onto the fixture base table and tighten the side screws.
  4. Place the sample into the TA-FSF making sure that the sample is centrally aligned with the aperture on the TA-FSF.
  5. Lower the cylinder probe and align it with the TA-FSF holder aperture such that it can penetrate the hole without touching the edges of the TA-FSF. Contact with the TA-FSF will result in instrument overload and termination of the test.
  6. Once the alignment is complete, tighten the screws of the fixture base table.
  7. Centrally position the sample to the hole of the TA-FSF and tighten it into position.
  8. Start the compression test.

Note: When optimising test settings, the hardest sample is best tested first in order to predict the maximum testing range for subsequent samples.

For comparison purposes, the samples placed in the TA-FSF must be centrally located under the hole and the orientation of the sample must be consistent.

Results

The graphs show the burst strength by penetration for two different types of pharmaceutical films using a 3 mm cylinder probe

Figure 1

Figure 1 shows the rupture test for Sample A and B (2.5 x 2.5 cm) using a 3 mm cylinder probe. The orientation of the test samples has been kept consistent, such that the shiny surface always faces the cylinder probe.

Figure 2

Figure 2 shows force vs. distance for the rupture test for Sample A and B. Penetration depth was 8 mm during which time the sample was ruptured before reaching the 8 mm distance. The probe then returned to its starting position (a few mm above the sample), indicated by the negative part of the graph.

Discussion

When a trigger force of 5 g is detected, the test commences. The probe proceeds to deform the sample to a deformation distance of 8 mm. The maximum peak observed represents the force required to cause the initial breaking of the film material. The area under the curve represents the hardness work done (energy required to rupture sample). Sample B is firmer than sample A requiring greater force to rupture the sample. Sample B is also more flexible, illustrated by the deformation at hardness values in the table below.

Tests obtained from 2 film samples of each type give the following Hardness, Deformation at Hardness and Hardness Work Done values below: