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Old Aug 30, 2010, 11:34 PM
tzyoung is offline
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What gives with "foam safe" CA


I guess that this is the place to post this since it pertains to vacuum bagged flying surfaces.
I sat down this evening to prep a set of horizontal stab cores for bagging. I cut these cores a couple of weeks ago from some Dow HiLoad 60. Usually I stick the panels together with Fabri-tac; however my bottle is pretty new and hasn't quite lost enough acetone to where I can glue foam without having to squirt a little glue out let it air a bit before applying. So I reached for a bottle of BSI super-gold thin foam safe CA and applied a small drop while squeezing the cores together. In seconds, I was staring at a hole through the cores down to the beds below.
To test my sanity I grabbed a nearby piece of depron on the workbench and dispensed a liberal drop onto the shiny surface... nothing. I then grabbed another depron chunk and swirled the edge lacking the heat formed skin in the glue drop... nothing.
So why does a foam with higher density and what I would consider superior material properties fare so poorly against a glue that claims on the bottle that it is 100% foam safe?
This could be a real problem especially if I was trying to field repair a delam. Fortunately, I can save this core with a little lightweight Spackle.
Anyone else had any similar issues?
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Old Aug 31, 2010, 09:10 AM
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ive had that happen a few times before; the only thing i can think of is that it gets way to hot when its curing and melts the foam away a bit. with smaller x-sextion glue joints it doesnt usually do that, but on glue joints that have a larger surface area it seems there is more heat that builds up in there.

or the foamsafe CA is sometimes "contaminated" with regular CA?

thats all i got...

unless somebody wants to get into chemistry... maybe theres some additive in the foam that when the humidity and temperature are just right the chemicals between the foam and the glue react and become a solvent to the foam structure.

^^^^ that last one was total BS but it could happen i guess.

it is irritating.

anyone else?

-david
Old Aug 31, 2010, 10:44 AM
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It's most likely just down to chemistry. Even "foamsafe" CA can't be completely inert, or it'd hold as well as water. It's just bad luck that this particular foam doesn't play well with the "foamsafe" CA. It's likely not a bad batch or anything particularly "wrong", just inconvenient.
Old Aug 31, 2010, 11:06 AM
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I have a feeling that it has something to do with the structure of the foam. It is denser meaning that the cell size is much smaller than the foams that I haven't had any issues with. I guess those smaller cells are more efficient at wicking the glue via capillary action allowing the solvents that do not play nicely with polystyrene more chances to attack the cross-links holding the foam together.
After thinking about it more, the Fabri-tac glue that I normally use for fanfold foam and even 25psi square edge, with no problems, has been especially rough on this HiLoad stuff. I guess I will just chalk it up to denser micro-structure.

-Trent
Old Aug 31, 2010, 04:28 PM
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Foam Safe


The thin Super-Gold is more "aggressive" than Super-Gold+. It will, under some conditions, produce a lot more heat when it cures, which can melt some foams. In this case, Super-Gold+ should have been applied to one core and then the cores joined together. A light mist of Insta-Set and you'd be done. You have to be careful using too much Insta-Set with the thin Super-Gold, which can create enough heat to melt some foams.
Old Sep 01, 2010, 11:22 PM
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Dang it Trent, another set of foam tails damaged! I hope those weren't the vertical cores that we ran out of....

I'm having the same issue with the foam safe as Trent and our glue supplier is the same. It sounds like heat with the thin is most of the problem, but maybe the glues are contaminated? The medium (Super-Gold+) doesn't exhibit the same problems, so maybe Charlee's explanation is spot on.
Old Sep 03, 2010, 08:06 PM
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I would venture a couple of different theories... First, the thinner CA has a higher level of solvent to lower viscosity. It may also be that the Hi-load raw material may not be as resistant to the solvent used when compared to another foam. Extruded foams can be a blend of chemistries to get desired properties so it may explain why depron and polystyrene survive but others may not.
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Old Sep 29, 2010, 01:36 AM
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Sounds like a simple chemical reaction producing heat to me. One time I created really nice 2nd degree burns on my fingertips in a matter of seconds. Do not try to apply CA to a sponge and then apply it to a project, at least with your fingers!

It was nasty, the glue was kicking off, melted the sponge into a sticky mess that melted right through my vinyl glove, it was all sticking to my fingertips, burning them really quick but sticking to them at the same time.
Old Sep 29, 2010, 02:56 PM
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Squirt a drop of CA on a scrap piece of Hiload 60 without kicker and see if it melts through the foam. If it does it's chemistry. If not, spray it with kicker and see how hot it gets. If it gets hot enough to melt, it's temperature.


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