New facility advances permeation testing for determining the barrier performance of polymers
Predicting the barrier performance of a polymer (elastomer, thermoplastic, thermosets and hybrid organic-inorganic systems) is not straight forward. Permeability can be altered substantially with a slight modification of morphology or with the addition of a thin coating layer to the material. Storage conditions amongst other factors also have an effect on permeation rates. To assure reliable assessment and interpretation, you would ideally run tests on multiple samples simultaneously.
Now, with the introduction of a new purpose-built versatile rig at TWI, industry is able to make fast and accurate predictions of barrier performance at elevated pressures. One current use of the system is for assessing high-end thermoplastics as corrosion barriers within lined pipe or as the hydrocarbon containment in flexible riser applications in the oil and gas production sector.
A team of specialists at TWI has designed and built a high-pressure facility for permeation testing of polymeric materials. The new rig allows materials to be tested with a variety of gas mixtures and then graded in terms of performance.
The rig expands existing measurement capabilities for polymers. It works by allowing four polymer discs to be exposed to gas mixtures at small pressure intervals up to 650 bar and temperatures up to 100◦C. Components of these mixtures such as carbon dioxide, methane and hydrogen sulphide pass through the polymer film at different rates and can be quantified using a gas chromatograph. These concentration-time profiles can be analysed to determine the permeability, diffusion and solubility, coefficients.
TWI plans future work using different columns or detectors, which will facilitate the detection of permanent gases (H2, O2, N2, CO, ), noble gases (Argon, Xenon, Neon, Helium, Krypton), hydrocarbons from C1 up to C10, or polar compounds such as H2O, NH3 and alcohols.