Analysers perform materials characterisation

The thermogravimetric analysers from Rubotherm, available in the UK and Ireland through Merrow Scientific, are able to characterise materials while subjected to extreme temperatures and pressures.

Traditionally, in order to characterise a material's suitability for an application at high temperatures and/or high pressures, several samples would be needed, each of which would be placed in its own pressure vessel.

These pressure vessels would subject the sample to a certain environment - for example raised pressure, raised temperature and a mix of gases or vapours.

This environment is designed to imitate the conditions that the material would be subjected to in its real-life application; for example, a polymer that is to be used in a deep-sea drilling application needs to resist degradation under those conditions.

Samples are then kept under these conditions for certain time periods, then removed and analysed.

There are some problems associated with this approach, including the need for multiple samples and multiple pressure vessels, the time required for sample taking, the health and safety implications and more importantly, the fact that readings are only taken at intervals, not continuously, so key events may be missed.

The Rubotherm gravimetric system allows a sample to be measured continuously in terms of its mass change while subjected to pressures, temperatures and corrosive environments.

The key to the instruments' performance is their magnetic coupling and control system, which allows the high precision balance to be located in a separate chamber from the sample.

With conventional instruments, a physical link between the sample and balance limits the range of application to pressures of typically 20 bar; whereas with Rubotherm systems pressures as high as 1,000 bar, temperatures greater than 1,500C and corrosive environments are possible while monitoring changes in the sample's mass.

Regarding the polymer application, a sample of polymer can be subjected to conditions likely to be experienced in its intended use, for example 1,000 bar and 200C while dosing sour gas over the sample.

Temperature and pressure ramping profiles effects can also be assessed.

This would allow the user to assess the suitability of the sample for downhole applications in the oil industry.

Other applications would include corrosion studies on metals and other materials and pyrolysis and gasification research.

Other versions of the Rubotherm systems can be used for a wide range of applications at raised pressures and temperatures including gas sorption, diffusion, surface area analysis of materials and fundamental measurements of gas densities.

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