Solubility Testing

Thermal Ceramics were the pioneers of today’s bio-soluble fibre products and have maintained that lead right up to the present day. Of the many developments required to support this programme, Thermal Ceramics R&D developed both static and dynamic solubility tests, which are important tools used in the development of all new fibres.

Static Solubility
This is a quick & simple test that is used to screen candidate fibre compositions & look at unknown fibres from the field. Basically a small sample of fibre is held at 37°C (body temperature) for 24hrs in a simulated body fluid. The solution is decanted & analysed for elements that have been leached from the fibre. The more Biosoluble the fibre the higher the level of materials are leached from the fibre sample. The results are recorded as ppm in the solution.

Dynamic Flow Test
This is a long term carefully controlled test that establishes more accurately the long term Biosolubility of a fibre & is usually used for testing commercially available fibres or candidates for commercialisation. This test is also conducted at 37°C, but the test lasts for 3 weeks. In this test the same simulated body fluid is pumped very slowly over a sample of fibre which has been normalised to its surface area. Thus fresh solution is always presented to the sample. The solution is collected & analysed twice weekly for the concentration of elements leached from the fibre sample. Thus we have a known surface area, known flow rate & known leachant concentration. All these components are put together to give a dissolution rate in ng/cm²hr which only depends upon the fibre composition. This is very important for comparing fibre types. Additionally it is easy to see if dissolution of the sample is uniform over the full 3 week period, which is especially important for a Low Biopersistent fibre. This dissolution rate is a measure of the Biosolubility of the fibre.

These 2 tests are an essential component in the Development of Biosoluble fibres & ensuring that what we produce today is truly Biosoluble.