October 1, 2017.
Thermal desorption spectroscopy (TDS) was used to monitor the outgassing as a function of temperature for polymers in the range of 30°C to 200°C. Mass spectra were taken while samples were heated in vacuum at 1°C per minute to the maximum temperature and held there for a dwell time of three hours. Samples of Buna-N and Viton A not exposed (ne), and exposed to high pressure (100MPa) helium and hydrogen (He/H2), and argon and hydrogen (Ar/H2) were studied. During these experiments Buna-N(ne) lost ~8% of its weight, Buna-N(Ar/H2) lost 18% of its weight, and Buna-N(HeH2) lost ~8% of its weight. All the Viton A samples lost
The mass spectra of the non-exposed samples show greater release of volatiles than the exposed samples. The samples exposed to Ar/H2 release less volatiles than those exposed to He/H2. In the graphs comparing pressure changes for Buna-N, all the samples peak at different temperatures. The (ne) sample peaks at ~85°C, while the exposed samples have a shoulder at ~90°C but do not peak until 200°C.
All of the Viton A samples have a peak at ~85°C with the ArH2 sample having a much higher amount of outgassing. The ArH2 shows increasing pressure when the sample gets to the 200°C dwell point implying a peak at higher temperature would release more tightly trapped species. The other two Viton sample show pressure is still falling at 200°C.
TDS has been shown to be a useful tool in the study of the effect of high pressure gases on these materials. Future work should include a more detailed examination of the time/temperature evolution of the individual masses seen in this data. There are plans for similar experiments using hydrogen only as well as experiments where the high pressure hydrogen is cycled.
Sandia National Laboratory/California (SNL)
This material is based upon work supported by the National Science Foundation through the Robert Noyce Teacher Scholarship Program under Grant # 1340110. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. The research was also made possible by the California State University STEM Teacher and Researcher Program, in partnership with Chevron (www.chevron.com), the National Marine Sanctuary Foundation (www.marinesanctuary.org) and Sandia National Laboratories.