Permeation Testing at TWI
TWI’s testing services are able to carry out liquid and gas permeation testing on ceramics, metals, polymers, and other materials used by industry.
Our services are designed to certify the service conditions of materials by measuring factors including permeability (the permeation coefficient), diffusivity (the diffusion coefficient) and solubility (the solubility coefficient).
TWI’s permeation experts are at the forefront of research as well as providing input into standards and best practice for industry. Our facilities include a range of bespoke and unique testing solutions that allow us to deliver in-depth testing results to our Industrial Members.
Measuring the barrier performance of polymers (elastomer, thermoplastic, thermosets and hybrid organic-inorganic systems) is not a simple process, as permeability transmission rates can be affected by even a slight modification, morphology, or the addition of a thin layer of coating to the material. Rates of permeation can also be impacted by storage conditions, among other factors, so multiple samples may need to be tested simultaneously in order to assure a reliable assessment for subsequent interpretation.
Testing Facilities
Our testing facilities include a unique rig that allows us to make fast and accurate barrier performance predictions at elevated pressures for industry. The high-pressure facility was purpose-built by our experts, allowing materials to be tested with a range of gas mixtures before being graded in terms of performance.
The bespoke testing cell has expanded our existing measurement capabilities for polymer testing and is able to accept different pipe geometries for testing. The rig works by exposing four polymer discs to gas mixtures at small pressure intervals of up to 650 bar and at temperatures up to 250◦C. The different components of gas mixtures, such as carbon dioxide, hydrogen sulphide and methane, pass through the polymer film at different rates, allowing them to be quantified by a gas chromatograph. These different permeation rates and concentration profiles can be analysed in order to ascertain the permeability, diffusion and solubility coefficients of different materials.
Using different columns and detectors, TWI can detect permanent gases (H2, O2, N2, CO), noble gases (Argon, Xenon, Neon, Helium, Krypton), hydrocarbons (from C1 up to C10), or polar compounds (H2O, NH3 and alcohols).
Among the testing undertaken at the cell are the assessment of high-end thermoplastics as corrosion barriers for lined pipes and measuring hydrocarbon containment in flexible riser applications for the oil and gas industry.
In addition to the services mentioned above, TWI can undertake sweet and sour gas permeation testing and has the facility to carry out finite element analysis (FEA) for more complex component shapes.
TWI can work to established industry standard test methods or utilise bespoke custom testing methods using relevant techniques for liquid and gas permeability.
Example Applications
TWI’s testing facilities have been used for a range of applications, including:
- Testing thermoplastic corrosion barriers for lined pipes
- Testing thermoplastic hydrocarbon barriers for flexible risers
- Assessing the suitability of heat exchanger seals for the food processing industry
- Waste repository testing
- Testing seals for LCD circuits
- Hydraulic and pneumatic seal testing
- Nuclear fusion – hydrogen seal testing
- Electronic encapsulation tests
- Testing for chemical processing industry applications
Technical Specification (Bespoke Permeation Testing Rig):
- Polymer discs simultaneously exposed to liquid mixtures (for a range of pipe geometries)
- Pressure up to 650 bar
- Temperature up to 250°C
- Allows the determination of permeation and diffusion coefficients
- Rate of permeation quantified using a gas chromatograph
- Gases that can be detected from mixtures include carbon dioxide, carbon monoxide, hydrogen, hydrogen sulphide, oxygen, methane, nitrogen, water, vapour, hydrocarbon vapours from C1 up to C10
For more information about TWI’s permeation testing services and how we can help you, please email contactus@twi.co.uk.