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In-situ investigation concerning the swelling behaviour of polymer materials under elevated pressures and temperatures
Dr. Margrit Junk
Nowadays, polymer materials are not only part of everyday life but are also essential in technical applications. In addition to the classic structural plastics, elastomeric materials are used, mainly as seals, in refrigeration technology. The basic properties of the materials as well as their consistent quality are essential for the long-term and failure-free operation of the systems and for the prevention of refrigerant losses.
The swelling behaviour of the polymers in contact with liquid or gaseous refrigerant (and with refrigeration oil) is an indicator of their resistance to the medium and thus an important parameter for the applicability of the materials. Until now, it was only possible to evaluate changes of the polymers, which were aged under increased gas pressure after their removal from the medium, i.e. AFTER the decompression phase. For the relevant behaviour of the materials DURING the media exposure and decompression, the data were previously only of limited significance. Here, the new in-situ measurement method will show its advantage.
The objective of the research project is to develop and set up a suitable test method for measuring the swelling or shrinkage process of polymer materials in situ under process conditions, i.e. during chemical and mechanical stress (p-T). Utilizing a see-through autoclave, a measurement system is to be configured that can be used for investigations in a temperature range up to 80 °C and for pressures up to 90 bar. Two alternative optical measurement methods will be used and compared. The first is a camera system for recording and measuring the time-dependent swelling behaviour of the samples. The second system is a high-speed 2D optical micrometer.
The measurement method should allow a time- and cost-saving evaluation of materials and provide a basis for the development of improved sealing materials. Thus, this research project contributes significantly to improving product sustainability and the safety of refrigeration systems.
The ILK is the leading institute for method development and investigations on material behaviour in the field of refrigeration technology. With the in-situ method, the existing test methods in the field of material aging and evaluation are supplemented by an innovative measurement procedure.