laminated glass tubes
 

Bernhard Kuemel wrote:

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.

Try? There is no "try." Do, or do not. 200 bar is 2900 psi, in
glass! If there is no boom today there will be boom tomorrow.

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.

Use polycarb with a weather package, like exterior use Uvex.
Hardcoating the outside (e.g, eyeglass lenses) can compromise shatter
resistance.

Can you recommend other materials to fill the gap? They should ...

Use tempered glass tubes for greater strength. Molten salt ion
exchange will temper a fully fabricated (empty) tube. However, any
added surface flaw will explode the tube. You still need a surface
coating - and you cannot do any glassblowing after tempering.

last very long (100+ years)

Use a thicker tube, temper it, then any applied protective surface
hardcoat. Go from borosilicate to aluminosilicate. That stuff is a
bitch to work in a flame.

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

You've got safety and aging issues. The usual approach is a
ruggedized tube inside an adequately thick, replaceable polycarbonate
shield assembly.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz4.htm