laminated glass tubes

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
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Why not make samples and test them by breaking them at 200 bar and seeing what the result is?
Any restriction on thickness (bullet -proof glass)? Any restriction on wire? http://www.fireglass.com/glass/wirelite-nt /
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Androcles wrote:

I do make explosion tests with display tubes filled to higher than normal pressure. But acquiring the materials costs money and making the pressure and protective tubes is a lot of work so I try to pick the ideal materials at first.

Not unless they remain practical. I'm currently thinking of 60 mm total outer diameter with 7 mm wall thickness for the outer tube, 1-3 mm gap material and 2 mm inner tube of the protective tube. That's 10-12 mm total wall thickness of the protective tube. Length is 20-25 cm.
The pressure tube within the protective tube is 10 mm OD.
But I could not find bullet proof glass *tubes*. I did find laminated glass tubes intended as pillars in building construction. However, they cost near 100 Euro per 25cm piece.
I thought of using laminated glass panes, which are easier to make. But a tube looks much better than a cuboid. Also how do I join the panes so they will not open at the edges when the pressure tube explodes.

The purpose is to watch the pressure tube in detail. So I will try without wires.
Bernhard
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If you use a thick-wall tube of toughened glass then why would you need a protective tube at all? Seems to me you are making hard work for yourself taking a precaution that is excessive, but then I don't know what your costs are. Have you approached any glass manufacturers and obtained quotes? http://tinyurl.com/y9442wu
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Bernhard Kuemel wrote:

What about a box that is metal on all sides but one, the latter being the laminated plate glass?
Or maybe metal on all sides with a video camera and lamp inside with the tube.
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