Geothermal energy is used for heating, cooling or conversion to other energy sources. This geothermal energy is obtainable near the earth surface in places like Iceland or New Zealand. However when not readily available one has to drill into the earth crust to reach for this energy. The deeper one gets the higher the water temperature and its inherent energy rating.
Temperatures of up to 300°C may be encountered in practice. At these extreme conditions the
lifetime of elastomeric seals based on carbon elastomers is shortened considerably.
Nanoparticles have been reported to increase the temperature1,2 and pressure resistance2 of Fluoro elastomer (FKM) compounds. Maiti et al1 described the use of nanoclay fillers to enhance the low and high thermal degradation of FKM compounds. In another study2 Multi-Walled carbon NanoTubes (MWNTs) were found to increase the temperature and pressure resistance of FKM and Perfluoro (FFKM) elastomers. Recently the synthesis and physical properties of a carbon nanotube (CNT) network was described3. The viscoelastic properties of this “nanotube-rubber” were found to be invariant over the temperature range -196°C – 1000°C.
The goal of this study is to study the influence of nanofillers on the temperature and pressure resistance of elastomer seals for geothermal applications
The graduate student will start with a literature search into the various kinds of nanoparticles incorporated in organic and inorganic polymers for high temperature and pressure applications. Besides the nanoparticles used the latest progress in elastomers for high temperature applications is of particular interest. Like for example elastomers developed for aviation, aerospace and gas and oil field exploration applications.
After selection the most promising nanofillers and elastomers will be mixed into compounds with a Toshin TD3-10MDX laboratory dispersion mixer or two roll mill.
Samples for mechanical and dynamic mechanical testing will be produced using a Jing Day laboratory press.
After preforming the compounds will be vulcanized to produce cylindrical prototype seals bonded to a metal shaft. These samples will be used for pressure testing and made in production.
The vulcanization characteristics of these compounds will be determined using a Montech DMDR-3000 rheometer.
The mechanical and dynamic mechanical properties will be characterized using an Instron 3366 tensile tester a Gabo Qualimeter Eplexor 500N respectively. The properties at elevated temperatures are of particular interest.
The pressure differentials these prototype seals can withstand will be tested at elevated temperatures in the pressure integrity (PIT) unit at RUMA. A schematic view of this unit is presented in Fig. 1. The metal core with the seal bonded to its surface is placed vertically in the test cylinder. Conventional seals (non-swollen) can be tested right away. Swellable seals are allowed to swell for a certain time at the test temperature.
Fig. 1 Schematic view of PIT-unit for pressure testing of seals at temperatures up to 300°C and pressure differentials of 150 bar.
After first contact between the swollen seal and the cylinder wall the seals are allowed an additional swell time for setting. Then the pressure differential ∆p is created between the fluid (water solution) above and below the seal. This differential is subsequently increased stepwise until failure.
The various new nanofiller compounds and reference compounds not containing any nanofiller will be tested in these PIT-tests for comparison of their pressure differential behaviour.
The graduation report should contain clear an precise conclusions regarding the influence of
- the kind of nanofiller
- the various high temperature elastomers
- used on the temperature and pressure resistance of high temperature and pressure seals. Furthermore
A preliminary planning for the work described above is given in Table 1. This planning is based on a nine month graduation project. If necessary the planning can be shortened by omitting the (dynamic)mechanical testing part.
Table 1 Estimated planning of the project described
mixing & sample preparation
dynamic mechanical testing
 M. Maiti, S. Mitra, A. Bhowmick: Effect of nanoclays on high and low temperature
degradation of fluoroelastomers, Polymer Degradation and Stability 93, 2008, 188-200.
 M. Endo, T. Noguchi, M. Ito, K. Takeuchi, T. Hayashi, Y.A. Kim, T. Wanibuchi, H. Jinnai,
M. Terrones and M. S. Dresselhaus: Extreme-Peformance Rubber Nanocomposites for
Probing and Excavating Deep Oil Resources Using Multi-Walled Carbon Nanotubes,
Adv. Funct. Mater. 19, 2008, 3403-3409.
 M. Xu, D.N. Futaba, T. Yamada, M. Yumura, K. Hata: Carbon Nanotubes with Temperature- Invariant Viscoelasticity from –196° to 1000°C, Science 3 December 2010: Vol. 330 no. 6009 pp. 1364-1368