some questions on fiberglass resin

[boostin302]

hello guys.

I have made a mold out of the expandable foam ( yellow top, red can) you get from walmart. it says its a polyurethane-based foam, can I use a polyester fiberglass resin over it to seal it up?

foam: http://www.walmart.com/ip/Great-Stuff-Big-Gap-Filler-12-Oz/17300795

resin: http://www.oreillyauto.com/site/c/detail/BDO0/402/N0486.oap?ck=Search_N0486_-1_156&pt=N0486&ppt=C0171

[ric006]

i wouldnt trust great stuff man

[SnowDrifter]

Could you get some sort of water based paint and put a couple layers on top before moving to the resin?

Squirt out a ball of foam and paint it in resin to see if it dissolves

[boostin302]

yeah i could get some water based paint if needed..

what would that do actually? besides maybe put a protective cover between the foam and resin

i know resin produces heat and i think only thing that could go bad, is the foam melting and running all over the place.

if that would be the case, could you mix in some extra hardener to get it set faster?

[Ben Fultz]

yeah i could get some water based paint if needed..

what would that do actually? besides maybe put a protective cover between the foam and resin

i know resin produces heat and i think only thing that could go bad, is the foam melting and running all over the place.

if that would be the case, could you mix in some extra hardener to get it set faster?

That's the opposite of what you want to do, the more catalyst you use the hotter it gets, that's why it sets quicker. Your speeding up the chemical reaction, creating more heat in the process. Also the hotter you mix it, the more brittle it also becomes.

[Rell]

Could you post pics of this mold? Do you plan on pulling multiple parts from this mold or just one? How big is it? Foam wouldn't exactly be the best thing to use a mold to pull parts from.

Im not sure on the exact differences between great stuff foam in a can from red top to yellow top.

But I can tell you first hand that I have take a cured cut off price of great stuff foam from the yellow top can. I mixed up a really hot batch of resin and applied it to the foam and let it cure. The foam did not distort, melt etc in any way.

I have heard of this foam melting with resin, however I'm not sure which of the cans people have used or if great stuff has made any changes to their product.

If you have sanded any part of the foam to shape it or need to fill in any voids you can use plaster of pairs and mix it up with water and apply light coats to the foam and sand it after letting it cure. Apply more costs if needed.

[boostin302]

i actually went out on a limb last night and emailed 3m (bondo) about it and they said that it should work perfect for my foam. since its a polyester resin and a polyurethane foam, it will work and cure to it right.

the mold is actually for sealing off the trunk.

if anything, i could just mix in a little bit less of hardener so the heat wont get that hot on it.

[boostin302]

so I went ahead and bit the bullet on it tonight. mixed up some resin and hardener to what was recommended on the box, applied it and its working perfect. not melting the foam any and curing up nicely.

only downfall I see is the foam just soaks up sooo much resin.

[audiofanaticz]

you wont have no issues. dont it tons of times already.