hello, err im told the shelf life for polyester resin is 6 months to 1 year, however im about to run out of fresh resin and i have some which is about 2 years old which i was reluctant to use but seems like i am going to have to…
what exactly happens to resin as it gets old? i know it has discoloured dramatically but what happens to the properties of the resin? will it react funny mixed with fresh resin? will it even cure? etc
thx
from my experience it starts to gell especially on top i have strained and used it succesefuly thining with styrene as needed i would catalyze some as a test before use also am not sure if it looses strength i personaly would not use on a structual part
if it is a big drum stand it up and ‘bubble’ the resin…
something we do to keep our resin well mixed… you just get a small steel pipe and attach the air to it… put it on about 10 psi ( low enough to keep the drum bubbling but not enough to make it explode…lol) … make sure its long enough to reach the bottom of the drum and just stick the pipe in there and leave it about… well, you said its 2 years old so maybe for an hour or so… what it does is because you are blowing air into it the bubbles rise to the top of the surface and in doing that it bring everything up from the bottom and thoroughly mixes the resin/wax/styrene etc together properly…
but as advantage said, just do a little test batch… what will you be using this resin for?
First what type of PER? Gel coat, lamination or what?
Do a gel time test with exact % of catalyst.
We have use 5 year old PER (sometimes we have to add some cobalt to juice up the curing, but use with extreme care) in the class as long as air has not gotten in the container. A trick here is to squirt a little nitrogen into the can with the lid partly off so it will at as a floater and prevent air to start degrading the resin.
I’m also told that you can pour some sort of thinner for PER (or silicone, etc…) into the container as a floater too.
Check out www.mmcontainers.com for some really trick buckets with unscrewable lids, trick inner seal, locks, folding handle, std. pull spourt and 8 sizes from 1/2 gallon to 11.3 gallons.
PS: On the air deal, I wouldn’t do it as it may inject water or oil into the resin. The best way would be to get a proper drum mixer that drops down the bung hole but a non sparking one. Maybe an air drill with a long shaft and some washers welded tothe shaft.
the air trick sounds like a good idea to me if my air is clean enough to spray gell and paint it should be good enough for the resin wish i would have thought of it before spending 375.00 on mixer i tried all kinds of home made mixers to go in the small hole but something was always breaking finaly just bought a mixer and was done with it must say it works well but a real pain to klean
theres only about 2kg there so its no big deal if i cant use it, im on my last layer of a mould i already got 5 done with new resin, and just need 1800 g of resin to finish the mould, no big deal if its lost a little of its strength i just need it to cure right so i can get this mould done.
ill do a cure test later see how long it takes to set, if it cures ok u guys think its ok to use?
Yes…
it would not bother me either (just kick it real hard to test it if it aint broke kick it harder) just kiddin
we were also worried about water getting into the resin but we use a regulator for the air so its all good…
we also had to be careful with the type of pipe we used as we didnt want it to be able to rust and contaminate the resin…
I think the resin should be fine and seeing as its a finisher layer of the mould you still have the rest of the better glass underneath it, and you can always fibreglass over it when you get newer fresher resin…