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laminated glass tubes
- 12-18-2009
- Bernhard Kuemel
December 18, 2009, 9:08 am
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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
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
Re: laminated glass tubes
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
Re: laminated glass tubes
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
Re: laminated glass tubes
CO2 is cheap and available. It has an excellent critical temperature.
You can make it critical with body heat or other low power heating and
cool it below critical with ambient temperature. It is non toxic, non
ozone depleting (influences availability). Its (super)critical pressure
is low enough so it can be contained in glass tubes.
CClF3 has great critical data (29°C, 39 bar), but it is ozone depleting
and hard to get. C2F6 has even lower pc (33 bar), but Tc is silghtly too
low (19 °C) so it would have to be cooled to go subcritical. It's
expensive (compared to CO2) and I would have to buy or rent a pressure
bottle. And even at 33 bar (or more if supercritical) a protective case
is very preferable. So I just use CO2. Supercritical CO2 is also used
industrially and so is particularly interesting for people to watch.
Ohh, BTW, Helium would be the safest candidate: 2.3 bar, but at 5 K. :)
Or something like C7F16 with 16 bar and 202 °C in an oil bath might be
an option.
Bernhard
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