Thermal outgassing of DC-93-500, a TWT encapsulant
Abstract
The silicone traveling wave tube (TWT) encapsulant DC 93-500 has been subjected to thermal/vacuum analyses to verify its thermal stability and determine the extent of outgassing at the most severe expected operating conditions. Some limited comparisions have been made with a potential substitute encapsulant, Sylgard-184. The thermal stability of 93-500 is entirely satisfactory under the conditions studied (120 C, vacuum, long term). Significant outgassing was detected. Sufficient characterization was carried out to identify the mechanism of outgassing as being due to hydrolysis of silane by residual water in 93-500 base resin. The reaction produces volatile mono-vinyl silanol with appreciable quantities of hydrogen as a byproduct. The possible influence of the outgassing on the ultimate mechanical properties is discussed, as well as the potential for contamination of adjacent optical surfaces, and the possibility of the reaction as a source of hydrogen within the tubes. Firm answers to the additional questions raised by this study are not presently available.
- Publication:
-
Final Report
- Pub Date:
- September 1979
- Bibcode:
- 1979aerc.rept.....G
- Keywords:
-
- Encapsulating;
- Outgassing;
- Silicone Resins;
- Thermal Stability;
- Traveling Wave Tubes;
- Long Term Effects;
- Plastic Coatings;
- Thermal Vacuum Tests;
- Thermogravimetry;
- Electronics and Electrical Engineering