Gorillia glue and epoxy

[freshtrax]

If I glue some frames, and laminate some parts are they ok to coat with epoxy later r will it affect the glue? White oak frames glued and screwed. Will be coating with east system s1 sealer.

[Gerarddm]

I'd be leery of Gorilla glue in that application.

[skaraborgcraft]

I use polyurethane glue a lot. What your planning to do seems fine,i have had no adverse effects from overcoating the glue with epoxy...BUT....i have never used that particular,Gorrilla, brand. Perhaps you could contact the makers and ask their opinion?

[Eddiebou]

This is not directly answering your question. 'Bout 15 yrs ago, when Gorilla glue first hit the shelves around here, I glued up some test pieces just for comparison.
I used Gorilla, poly in a caulking tube (don't know what brand), and Titebond II. I simply glued two small pieces of white pine (maybe 3/4x 1 1/2x 8) perpendicular to each other and clamped them for 24 hrs. The poly in the tube and the titebond both held strong enough that the wood fractured. The gorilla glue itself fractured. The foamy glue joint parted and left the wood intact. I haven't used it since.

[skaraborgcraft]

Fair comment,as i said,i have no experience with Gorrilla,and therefore must therefore conclude all polyurethane glues are not the same. I had some test pieces of ply and fir that went through 6 months of wet and drying cyles...the timber failed in both cases. You could always use a powdered resin,resourcinal glue on your frames if cost is an issue.

[Dan McCosh]

I used Gorilla glue to glue some deck-beam scarfs, a decision that resulted in removing 30 or so deck beams and replacing them. The stuff is a poor laminating glue for several reasons--it has little inherent strength, and the foaming action tends to blow the glue out of the joint. It is both unpredictable and unreliable.

[Bob Smalser]

After some testing, I've done quite a bit of lamination using liquid polurethane glues, and have not had any problems at all in as long as ten years service in boats left out in the weather. It's especially good for damp lams that have just come from the steambox like these Doug Fir knees. And if you catch it before it fully hardens, it's an easy cleanup, even to the point of running unscraped glue joints through the planer, which with other glues likes to chip the knives.



Don't be fooled by the foaming. It won't fill gaps and it requires lots of clamping pressure. As the wood gets wetter, the bonds get weaker, so I'd refrain from gluing wood much above 20% without drying it first. Tests say it's a weak glue compared to the others, but "strength" in glues is badly over-rated, as all of them are stronger than the wood they are bonding.

It also bonds with epoxy well, so you can fill any voids with fairing compound without problems.

[Boston]

test pieces
test pieces
test pieces

might be your best bet to answer your question

You might think of just going with one of the more traditional glues like epoxy or resorcinol and eliminating some of the worry.

I'm not familiar with East system products, but coating epoxy with epoxy is fine as is coating Rorscinol with epoxy.

[RodB]

After some testing, I've done quite a bit of lamination using liquid polurethane glues, and have not had any problems at all in as long as ten years service in boats left out in the weather. It's especially good for damp lams that have just come from the steambox like these Doug Fir knees. And if you catch it before it fully hardens, it's an easy cleanup, even to the point of running unscraped glue joints through the planer, which with other glues likes to chip the knives.

I'm curious Bob... would you recommend Gorilla Glue specifically... ? I have used PL premium and it seems quite a different animal than Gorilla glue. There have been many anecdotal related experiences of Gorilla Glue failure on this forum and I'm wondering if you would include it unequivocally with the rest of the polyurathane glues?

Many on this and other forums have sworn off of Gorilla Glue... like "not in my shop any more"...

Just curious...

RodB

[Bob Smalser]

I'm not recommending it at all over rated marine glues.

My point is that properly used, it's another tool in your kit in situations where moisture contents are higher than the 12% required for epoxy and the 15% required for resorcinol. I've found it will glue green wood at 30% MC, providing that wood isn't dripping wet with surface water. But as I said, the wetter the wood, the weaker the bond.

Nor can I account for others' failures using it. Except that it requires clamping pressures similar to resorcinol, and exceptionally dry wood requires a wipe with a damp rag to provide the moisture it needs to properly cure. Forumite Lucky Luke in Vietnam built a large yacht using liquid poly, albeit with the lams backed up by fasteners.

PL Premium is the same glue, only mixed with mineral fillers with a lot of cyano added to it. While easier to use, it isn't problem-free either, as in warm weather its open time is insufficient for large lamination jobs.

Also notice I only used it in non-critical parts that are easily replaced should they fail. But in 10 years service, none of them have.

[RodB]

Thanks Bob for the qualificaton of your remarks.. and the "moisture content input.

RodB

[freshtrax]

After further research I think I will use pl premium fast tack. Along with stainless fasteners. Thanks for the input everyone.

[Boston]

stainless is subject to crevice corrosion, isn't approved for bellow the waterline use.

cheers
B

[freshtrax]

I understand that. Not too concerned about it for this application.

[Concordia 33]

This is not directly answering your question. 'Bout 15 yrs ago, when Gorilla glue first hit the shelves around here, I glued up some test pieces just for comparison.
I used Gorilla, poly in a caulking tube (don't know what brand), and Titebond II. I simply glued two small pieces of white pine (maybe 3/4x 1 1/2x 8) perpendicular to each other and clamped them for 24 hrs. The poly in the tube and the titebond both held strong enough that the wood fractured. The gorilla glue itself fractured. The foamy glue joint parted and left the wood intact. I haven't used it since.

I've not had that problem with gorilla glue, but it like epoxy does not do well with over-clamping. I went to a talk at the Classic Yacht Symposium by someone form the Gougeon Brothers - They were talking more about the characteristics of wood, but we started to talk glue and got into a discussion of Epoxy vs. Gorilla Glue - they seemed to feel that in situations where the wood would not be subjected to a high amount of flexing, that Gorilla Glue was comparable to epoxy. I like it when I am gluing two irregular pieces as the Glue will foam into the small voids and has good adhesion and good cohesion.

[David G]

C33,

I'm afraid you've got it backwards. Liquid polyurethane glues, like Gorilla Glue, DO need a good amount of clamping pressure. Any gaps - from bad workmanship, or underclamping - WILL fill with foamy glue. That foamy glue, however, has very little strength. In other words - it's not gap-filling, in any useful way.

I'm one who doesn't use it and doesn't plan to use it normally. I don't like the way it was oversold - both as the 'strongest glue around' (which it patently is not... just the opposite, in fact)... and as a gap-filling adhesive. I could see myself picking some up, if I had some sort of odd application where its moisture-curing attributes made it the logical choice, and where the strength issue wasn't key. I don't see that happening often... or maybe ever.

[Geoff C]

Read what TheChemist had to say about it on this old thread:

John Gearing
.
Member # 47
posted 12-08-2002 03:29 PM
I've taken the liberty of pulling thechemist's comments out of
the previous thread on polyurethane glue (the one thechemist
refers to above)....
posted 06-12-2000 10:01 PM
--------------------------------------
The term "Polyurethane" glue means a lot of different things,
as you can see from the foregoing. that is because the guys
who write the hype for these products play fast and loose with
nomenclature and mostly don't know a carbonyl group from a
free radical, and would not recognize a urethane linkage if it
bit them on the nose. They work in Marketing. They keep their
consciences in a jar in the closet.
Very simply, glue is chains of atoms with some characteristic
structures along the length of it (the backbone, if you will)
and some other characteristic structure (a Functional group)
on the ends. After time exposed to the air, or after mixing
two components, Things Happen.
Maybe water vapor or oxygen in the air is the second
component, or something evaporates out of the glue, allowing
Things to Happen.
The result of Things Happening is that, after Everything Has
Happened, All those little molecular chains are stuck together
into one big molecule about a hundred miles long with more
branches and entanglements than the Interstate Highway System.
Bits of molecular hair are stuck out of the Big Molecular
Hairball everywhere, and they are more sticky than anything
you could imagine. They stick 'most anything they touch into
the Big Molecular Hairball and thus are all stuck to each
other.
Some glues are very rubbery, such as 3M 5200. Some are
relatively hard, such West System epoxy, Gorilla Glue or
resorcinol. The hardness has to do with the relative length of
the molecular chains this all started with, and how many
Functional Groups there are on each end and maybe branches
along the length. If there was only on each end one thing that
could connect to one other, you can see that we would grow
only longer molecular strands after Things Had Happened, and
our Big Molecular Hairball would have all the cohesiveness of
a plate of oiled spaghetti. The harder glues are made from
relatively short chains with many branches, so as to form a
rigid three-dimensional structure.
The Urethane reaction was discovered by Otto Bayer in 1938. It
consisted of a hydroxyl on one end of a molecule reacting with
an isocyanate on another end of another molecule to form a (I
cannot exactly draw it here, but one molecular chain has a
nitrogen with a hydrogen on it, the nitrogen further connected
to a carbon with a double-bonded oxygen connected to it, the
carbon further connected to an oxygen which was of the
original hydroxyl, that further connected to whatever the
original hydroxyl was connected to.) characteristic NHCOO
linkage in the middle of the chain. This is a urethane
linkage. A molecular chain may be made up of these
here-and-there in the backbone and yet be a conventional
varnish in all other respects, and some guy calls it a
urethane varnish. The boss says, wait a minute, I want a name
of my own. Call it Varathane. There ya go.
The urethane prepolymer chains may have silanol groups on the
end, as do most commercial caulks, and these react with each
other two or three times on each chain end, as well as
sticking to anything else they touch. Well, it does not cure
by the urethane reaction but it has some urethane in the
backbone so it is called a urethane glue.
Earl Scheib, famous for his "Yeah! I'll paint any car for
$99.95! And for an extra twenty dollars I'll even throw in
Polyurethane! [as the guy in the backgrouhd, dressed in a
chemist's lab, coat pours a clear glass cylinder of some clear
liquid into a can of paint] car painting television
commercials, had some other stuff. Polyurethane paint,
evidently.
The urethane glue may have no urethane in it but only
isocyanate-terminated molecular chains. Isocyanates react with
moisture in the air to form amines, with the liberation of a
molecule of carbon dioxide gas (aha!, you say...yes...but
wait...) and the resulting amine reacts with two other
isocyanates to form ureas (NHCONH, something like a urethane )
and the whole thing becomes the Big Molecular Hairball as
these Things Happen.
The Functional Groups have a lot to do with how sticky the
glues are. Isocyanate-terminated glues will react with the
moisture in the air and may, if there is enough isocyanate
present, show foaming when cured. No foaming is not proof of
no isocyanate, but suggestive.
Small isocyanate molecules are Bad Things To Breathe. Such is
in the Gorilla Glue, and maybe others, but I am not sure. Look
on the label in the fine print and see if it warns that it
contains isocyanates of any sort. You will need a magnifying
glass to find these warnings, usually.

I will try to find the Gorilla Glue diatribe and paste it in
here.
chemist
posted 03-07-2000 08:59 PM
------------------------------------------
Gorilla Glue is a mixture of monomeric and polymeric (meaning
three or four monomer molecules hooked together) methylene
diphenyl diisocyanate (MDI). The monomer content is a critical
health issue. The vapor pressure of the monomer is such that
if there is more than about twenty percent monomer in this
stuff, then it will exceed the safe exposure limit of fifty
parts per BILLION for MDI, which is considered a VERY strong
sensitizer. The ACGIH (American Council of Government and
Industrial Hygenists) does research and sets these limits. You
should believe them. The Gorilla glue MSDS and literature I
have seen says the stuff is safe and so forth, but that is in
the fully cured state only. They may not make this
distinction.
MDI will bond most woods well enough for some applications,
but should have tight joints. Isocyanates react with moisture
to liberate carbon dioxide gas and form polyureas when
reacting with themselves. The foamed polyurea may be weaker
than the wood. Exterior grade plywood is made by spreading a
thin film of MDI (The Gorilla just buys this stuff in drums
and repackages it) on the wood laminations and then the stack
goes into a press and that goes into an autoclave where it is
cured under pressure, heat, and live steam. So, for some
applications it is great stuff. Used in a controlled
industrial environment it yields an excellent product and the
stuff is cheap to make. Personally, I would never offer such a
product to the public because the permissible exposure level
(PEL) is too close to what a user gets when using the product
as recommended.
Go look at the label. Do they tell you to wear a gas mask with
an isocyanate-rated filter cartridge and not to get it on your
hands and what can happen if you do get it on your hands? Hah.
I'll tell you what happens when you do get it on your moist
little hands: The isocyanate reacts with the moisture to form
amines, and in the presence of excess moisture some amines are
left over that the other isocyanates do not find. The result
of that is that you now have on your hands methylene
dianiline, which is a really excellent and very efective
carcinogen. The safe exposure level for that stuff is "run
away at high speed".
Aside from those details, it can be a useful product. Wear
gloves and keep the wind at your back.

[David G]

Geoff,

Great retrospective, and good info. Reaffirms my decision to leave it alone for most applications.

[Boston]

well Geoff if this thing had a two thumbs up in it somewhere I'd give em to yah. Nice post and great stuff on the potential health risks

I have a small bottle of Gorilla glue around here the girl bought to fix her shoes with, gave me the left overs. Never tried it but it did seem to fix the shoes ok. I'm pretty comfortable with either peanut based epoxy or TB-2 or 3 mostly 2 and really have no reason to use the stuff. So I'd have to ask why even bother, TB-2 is cheap and if I need something more structural I just go with epoxy. My one issue with TB-2 is it doesn't stick to itself once dried very well, so if you loose a joint, you get to start over.

[Geoff C]

I found it interesting what The Chemist said about isocyanates and amines forming toxic compounds. Could it be that when people become sensitized to epoxy it is the amine blush that causes the allergic reaction? I've always used the non-blushing stuff in case this is true.

My wife bought a bottle of GG a while back but I don't use it in the shop.