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post #1 of 10 Old 09-04-2018, 11:53 AM Thread Starter
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Polyurethane

What is the shelf life (use by date) of an unopened can of Polyurethane?

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post #2 of 10 Old 09-04-2018, 12:04 PM
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What is the shelf life (use by date) of an unopened can of Polyurethane?
Like anything else it would depend on the brand and temperature it was stored. A good brand kept in a cool place could last decades where a bad brand kept someplace hot might only last a year. I keep paints I don't expect to use often in a refrigerator. Also what would help is if a person had a shaker. If the paint was shaken periodically it would also extend the life. Often when solvent coatings sit for a long time the thinner comes to the surface and the hardening oils settle to the bottom and can actually harden in the can with paint thinner floating on top.
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post #3 of 10 Old 09-04-2018, 02:38 PM
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I have a couple of gallons of Red Devil poly that are over 30 years old and are still good


But when ever I am about to reseal a can I spray a little bit of refrigerant in the can to displace the oxygen, makes them last mo better


You could use the "liquid air" things they sell in office supply stores, they are mostly R134a, at least they used to be. Always amazed me if working on refrigeration or comfort cooling we had to recover all the refrigerants, but in the office they can spray all they want without any ozone depletion

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post #4 of 10 Old 09-05-2018, 02:27 AM
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I have a couple of gallons of Red Devil poly that are over 30 years old and are still good


But when ever I am about to reseal a can I spray a little bit of refrigerant in the can to displace the oxygen, makes them last mo better


You could use the "liquid air" things they sell in office supply stores, they are mostly R134a, at least they used to be. Always amazed me if working on refrigeration or comfort cooling we had to recover all the refrigerants, but in the office they can spray all they want without any ozone depletion
The stuff they sell commercially, Bloxogen is, according to the ads, Argon. How does that compare? It has to be heavier than air so it blankets the top of the liquid. I have never tried it but I have considered using it. I don't think it works for water base stuff.

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post #5 of 10 Old 09-05-2018, 06:00 AM
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Unopened? Probably until the can rusts through and lets air in. Poly needs the air to cure after all, so it stands to reason that no air means no curing which means usable. That said, you probably dont want to assume a 50 year old can of poly will work fine, im sure some of the components break down with age. Minwax says their poly is good for a 5 year shelf life unopened, id use that as my number

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post #6 of 10 Old 09-05-2018, 02:30 PM
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The stuff they sell commercially, Bloxogen is, according to the ads, Argon. How does that compare? It has to be heavier than air so it blankets the top of the liquid. I have never tried it but I have considered using it. I don't think it works for water base stuff.

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Anything to replace the air with oxygen in it, it is the oxygen that does stuff in


When ever I have some old finish or adhesive I will do a trial run before applying to the finished project

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post #7 of 10 Old 12-18-2018, 08:29 PM
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The stuff they sell commercially, Bloxogen is, according to the ads, Argon. How does that compare? It has to be heavier than air so it blankets the top of the liquid. I have never tried it but I have considered using it. I don't think it works for water base stuff.

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Interesting. I would not recommend " dust off" or like air in a can. Why, because the " dust off" gas is a mix of ozone safe halogen gases. The big issue is that you place a blanket of this gas on top a half can of varnish or poly, the gas dissoves in the varnish and causes a vacuum. This vacuum is strong enough to crush or severely deform the can.


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post #8 of 10 Old 12-19-2018, 11:00 AM
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Interesting. I would not recommend " dust off" or like air in a can. Why, because the " dust off" gas is a mix of ozone safe halogen gases. The big issue is that you place a blanket of this gas on top a half can of varnish or poly, the gas dissoves in the varnish and causes a vacuum. This vacuum is strong enough to crush or severely deform the can.


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It does work and doesn't hurt the can, I use some R500 that I have had for umpteen years, and not worth finding a use for it, just a little puff of it and it lays on top of the contents in the can and keeps it from skinning over


I don't think the 134a they use in the keyboard dusters has any halogenated gases, it was halogenated chlorine that took the world from 4 refrigerants to the 30+ we have to deal with now, so you honestly have no idea what refrigerant is in a unit, probably a mixture of a few, which ruins the efficiency of the machine so we end up with more carbon in the atmosphere



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post #9 of 10 Old 12-19-2018, 11:07 AM
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One old time trick to help save the contents of an opened can is to put enough clean rocks in it to fill it to the top and displace the air.
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post #10 of 10 Old 12-19-2018, 01:41 PM
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One old time trick to help save the contents of an opened can is to put enough clean rocks in it to fill it to the top and displace the air.
Clean marbles or golf balls?

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