Long Lasting Adhesive/Sealant

[ARMY1]

I am looking for an adhesive/sealant that can withstand rugged environmental conditions and have a shelf-life of 20 years. Regardless of price, I am looking for the longest lasting adhesive/sealant available. The application for this sealant will be to seal a metal container (standard ASTM 1008) closed and be able to maintain an internal pressure of 3 psi. The sealant must be ductile enough to allow normal expansion/contraction of metal during changing atmospheric conditions. Some sealants currently being analyzed are liquid-poured silicones that harden with a tensile strength of approx. 250psi.

 

[Compositepro]

Silicone is probably you best bet, but much depends on the mechanical design of the joint as well as the adhesive. By 20 year shelf life I assume you mean for the sealed container and not for the uncured adhesive. All polymer have some permeability so maintaining 3 psi for 20 years is not likely but that is also probably not what you mean.

 

[amorrison]

Check into "acoustic sealant"
It does not have much strength but is supposed to stay "soft" indefinitely.
By designing the "pressure X area" to be small you will not require much strength.

 

[stephenweinstein]

About 5000 years ago, the ancient Egyptians sealed a pyramid so well that the air inside was studied by modern scientists to see what air was like at that time. This chamber and a bubble trapped under the polar ice cap were the oldest two known samples of air isolated from the rest of the atmosphere. Find out what the Egyptians used; if it did not leak even trace amounts, even after approximately 5000 years, this would almostly certainly be the ultimate record for the longest proven life for any seal. Here are some other ideas:

1. I would imagine that the longest life requirement for any adhesive or sealant application would be for the containers that will be used to store nuclear waste at Yucca (not sure of the spelling) Mountain. Find out what they use.

2. If cost is not an issue, you could weld the lids onto the containers.

3. The Romans built an aquaduct in Spain that still carried water when I heard about it over 2500 years ago later. Find out what they used.

4. In the 1960's, it was popular to store food in a nuclear fallout shelter that would last until the radiation subsided (remember the movie a few years ago about the child who has been raised underground because his parents confused a plane crash for a nuclear attack). Some of these foodstuffs did not last (someone went into one of the shelters about 20 years later and found that the chocolate bar that had been left behind by mistake was edible but the food that that was supposed to be there was not), but some probably did survive. Find out what was used to seal the containers.