Hi!
I make display glass tubes with high pressure content (up to 200 bar). To protect the tubes from damage and to protect the spectators from shrapnel in case of an explosion I try to make a protective cover.
Previously I used polycarbonate tube which is strong enough, but is easy to scratch and may turn brittle eventually. So I'm looking for something that will last 100+ years. I try to make laminated glass tubes. Filling the 1-3mm gap between concentric glass tubes with polyester produced bubbles as the polyester shrunk when it set.
Can you recommend other materials to fill the gap? They should ...
last very long (100+ years) excellent optical clarity The temperature range might be -40 °C (cold weather) to 70 °C (inside a car in full sun).
Preferably they should be...
tough low viscosity so I can get them in the gap index of refraction and thermal expansion similar to borosilicate glass
- 1,52 and 5 * 10^?6 not too expensive
Currently I'm thinking of ...
1) hydrocarbon gel such as in gel candles. It might be fluid enough so it will not detach from the glass surfaces when its volume grows and shrinks with varying temperature. But I'm afraid the hydrocarbons might evaporate.2) crystal clear polyurethane resin.
3) crystal clear silicone or modified silicone/silane (MS-polymer)4) Other crystal clear sealants
Actually just a simple (viscous) liquid (glycerol) might do the job, if it could be sealed in the gap reliably.
Thanks, Bernhard