Use with hydrogen:
Vacseal® has been used to make seals for hydrogen gas and it has also be used to contain liquid hydrogen. The real question though is now well it does do this and on that point we have difficulty giving an unambiguous answer. With any container there will be some kind of leak rate, and this is going to be no exception, but in at least some applications, the use of Vacseal® seems to be quite acceptable.
Use in threaded joints:
Assuming the application is with a UHV (ultra high vacuum) system, and of course, the use of such joints in a UHV system is generally discouraged, in theory it could be used. Indeed Vacseal® has been used with threaded joints but not for UHV applications. The connection must be made “wet" and once the Vacseal® has started to cure, making the joint will become all that much more difficult, and the end result will probably be found to be less than satisfactory. The reason is that Vacseal® cures by evaporation of the solvent, yet some amount of solvent is required to make the polymer flow as a liquid into the crevices of the joint. High vacuum joints pose particularly frustrating issues, since the tendency is for the curing to begin at the outside and progress inward. The cured portion of the joint then acts as a barrier to the further evaporation of the solvent, and the result is that there is a very slow rate of solvent evaporation for a very long time, possibly years.
Removal of Vacseal:
Unlike other vacuum sealing products, the resulting polymer formed can be removed with a number of hydrocarbon solvents. The uncured polymer can be wiped away or otherwise removed with toluene, whereas the cured polymer requires something stronger, such as methyl ethyl ketone (MEK), or in extreme cases, methylene chloride. For applications not requiring high cleanliness, many common paint or lacquer thinners will work equally as well. However, common sense must always prevail, and if the Vacseal® is to be removed from a plastic substrate, for example, then some careful testing must be done first, in order to make sure that the solvent does not damage the underlying plastic.
Finding the leak:
Various and expensive leak detection equipment can be used to find vacuum leaks. One “quick and dirty" solution which can be done in a matter of minutes and without spending a huge amount of money for an expensive leak detection system is to take advantage of the surface chemical properties of Liqui-Nox which can be used in conjunction with the easily understood “bubble test".
Product shelf-life and stability:
Vacseal® has a limited shelf life. On the shelf while still in unopened bottles, and being stored at room temperature and out of direct sunlight, the shelf life could be expected to be a minimum of three years. However the liquid product in quart cans has a shelf life of only three months. Hence be sure to give serious thought to the purchase Vacseal® in bulk quantities. Unless the product is destined for use almost immediately, we would recommend the purchase of the smaller bottles instead of the individual larger bottles or bulk cans. Shelf life of the product in aerosol cans is less than that in bottles.
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