GRP vacuum container?

Is it possible to make a vacuum cantainer with PE & mat that will keep a vacuum for 20yrs plus? Sure it will do it over a couple of days but fibreglass in porous and even to water? So how long it contain a vacuum?

Guess gel-coated surfaces and resin rich mat will help?

 

To start with, what kind of negative pressure do you need? Perfect vacuum is not attainable.

 

12psi would be sufficient.

 

FRP has solvents that will evaporate slowly. That will lower the vacuum with time. A metal or glass container would be more appropriate.

 

thanks,

 

20 yrs is a long vacuum time. Are you preserving something ?

 

thermal insulation, have switched to epoxy.

 

Interesting concept. How much better is it than say thick styrofoam, especially costwise.

Is it a big area to keep cool ?

 

I'm interested too, what's the application re thermal insulation? Maybe it's gotta be extraordinarily strong to resist? Jeff.

 

It might depend on what you are using it for and how you go about making it. With a constant vacuum inside, meaning constant pressure on the outside, I would imagine over time a fiberglass surface will deform. So if you were to use it for walls, after awhile they might look bad, used hidden or where looks didn't matter, like a fish hold, it might be OK.

http://en.wikipedia.org/wiki/Vacuum_insulated_panel

Things like these...
http://www.panasonic.com/industrial.../vacuum-insulation/vacuuminsulation-group.gif ... I believe start with some sort of inner structure like foam etc. They aren't hollow like a "thermos" type liner, so any possible thermal advantage should be balanced against weight and cost, in that you would have the weight of a foam core plus the extra weight of skins strengthened against the vacuum.

 

Vacuume panels apparently are significantly better at insulating than insulating foam, or synthetic foams. From what little I found, they have R values more than 10 times better than the best insulating foams, so I would guess would be far superior to typical core foams. That being said they are very expensive relatively, so you get about the same R value per dollar spent.

I can't see their application in a boat due to their major limitations in shape and size, but it might be possible to design a double hulled structure with them... But it seems like the cost would far exceed the cost to assume lower R value and just install larger HVAC systems.

 

In industrial applications vacuum insulation is used sometimes. However this is many times used in very high or very low temperatures, where composites do not perform.

I have once been asked to calculate a vessel, fairly large. It was reckoned that a vacuum pump would need 3 days to evacuate all air. (moleculair turbine pump)