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H2O outgassing from silica-filled polysiloxane TR55.
L N Dinh1, M A Schildbach, R S Maxwell
1Chemistry and Materials Science Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94551, USA. dihn1@llnl.gov
Journal of Colloid and Interface Science
|May 4, 2004
Summary
Moisture in TR55 polysiloxane is mainly chemisorbed water, slowly outgassing over decades. Physisorbed water, however, is easily removed within hours at elevated temperatures.
Area of Science:
- Materials Science
- Polymer Chemistry
- Surface Science
Background:
- Silica-filled cross-linked polysiloxanes like TR55 are used in various applications.
- Understanding their moisture content and outgassing behavior is crucial for performance and reliability.
Purpose of the Study:
- To quantify the total moisture content in TR55.
- To differentiate between physisorbed and chemisorbed water.
- To determine the outgassing kinetics of both water species.
Main Methods:
- Temperature-Programmed Desorption/Decomposition (TPD) was utilized.
- Analysis of moisture content and outgassing rates.
- Kinetic modeling of water desorption.
Main Results:
- TR55 exhibits a total moisture content of approximately 0.35 wt%.
- Chemisorbed water constitutes the majority (86.8%) of the moisture.
- Physisorbed water (13.2%) desorbs rapidly around 400 K, while chemisorbed water desorbs slowly over decades.
Conclusions:
- The long-term outgassing of TR55 is dominated by slowly desorbing chemisorbed water.
- Effective removal of physisorbed water can be achieved through vacuum pumping at moderate temperatures.
- Understanding these moisture dynamics is key for material selection and processing in vacuum environments.