Compatibility of polymers in super-critical carbon dioxide for power generation systems: High level findings for low temperatures and pressure conditions
- Sandia National Lab. (SNL-CA), Livermore, CA (United States)
- Univ. of Wisconsin, Madison, WI (United States)
Polymers such as PTFE (polytetrafluorethylene or Teflon), PEEK (polyetheretherketone), EPDM (ethylene propylene cliene monomer) rubber, Viton, EPR (ethylene propylene rubber), Nylon, Nitrile rubber, and perfluoroelastomers are commonly employed in super critical CO2 (sCO2) energy conversion systems. O-rings and gaskets made from these polymers face stringent performance conditions such as elevated temperatures, high pressures, pollutants and corrosive humid environments. Critical knowledge gaps about polymer degradation from sCO2 exposure need to be addressed. To understand these effects, we have studied nine commonly used polymers subjected to elevated temperatures under isobaric conditions of sCO2 pressure. The polymers (PEEK, Nylon, PTFE, EPDM, Nitrile rubber, EPR, Neoprene, perfluoroelastomer FF 202 and Viton) were exposed for 1000 hours at 100°C to 25 MPa sCO2 pressure in an autoclave. In a second study, elastomers perfluoroelastomer (FF202) and EPDM were exposed to 25 MPa sCO2 for 1000 hours at 150°C. Samples were extracted for ex-situ characterization at t = 200 hours and then at the completion of the test at t=1000 hours. The polymer samples were examined for physical and chemical changes by Dynamic Mechanical and Thermal Analysis (DMTA), Fourier Transform Infrared (FTIR) spectroscopy, and compression set. Density and mass changes immediately after removal from test and 48 hours later, and optical microscopy techniques were also used. Microcomputer tomography (micro CI) data was generated on select specimens. Super-critical CO2 effects have been identified as either physical or chemical effects. For each polymer, the dominance of one type of effect over the other was evaluated. Attempts were also made to qualitatively link sCO2 effects such as lowering or increase in glass transition temperatures, storage modulus changes, mass and compression set changes, chemical changes seen in FTIR analyses and blister and void formation seen post-exposure to polymer microstructure-related mechanisms such as plasticization of the polymer matrix, escape of volatiles from the polymer during depressurization, and filler and plasticizer effects on microstructure with rapid depressurization rates.
- Research Organization:
- Sandia National Lab. (SNL-CA), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- DOE Contract Number:
- AC04-94AL85000; NA0003525
- OSTI ID:
- 1592964
- Report Number(s):
- SAND-2019-14400R; 682612
- Country of Publication:
- United States
- Language:
- English
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