Hi, this is Sean here from 3M. Thanks for joining us today. As you can imagine we
get a ton of questions from out in the field about adhesives so, I've compiled a
top 10 list here and I'm going to tick these things off one at a time.
So let's start with one of the obvious questions: What's the difference between
these adhesives. So we've got three different adhesives.
We've got one structural adhesive and then two panel bonding adhesives. What is
the difference? and I'll address that in a second, but it may help to know what
the similarities are first. So these are very chemically similar in a lot of ways.
Number 1: The chemistry is epoxy, so all three of these products are
epoxies. Nice thing about epoxies is they handle heat very well. So there's a
number of things we can take advantage with because they handle the heat well.
Number 2: they all contain glass beads. those glass beads are in that product
to guarantee us a minimum bond line thickness, so we can't squeeze all the
adhesive out if we happen to over clamp. Number 3: they all have corrosion
inhibitors. So you should be very confident about using these products and
if they're applied correctly, and you cover all the bare metal, you should not
have any corrosion issues, even years down the road. So again, a lot of
similarities between these products to begin with. Now let's talk about some
very important differences. As I mentioned, we have one structural
adhesive and two panel bonding adhesives, and there's a large difference between
those two. So a structural adhesive is designed only to be used where the
manufacturers tell us to use it. So you're going to need to specifically go
to each procedure, for each vehicle, and specific year, and find out where they
recommend a structural adhesive. We don't want to use that just anywhere we feel
is suitable. We have to follow the OEM recommendations, and one of the reasons
is that it's a completely different style of adhesive. So it's got a lot of
technology in this, including that it's impact-resistant
or crash toughened. And what that means is it's got a little more give to it than a
traditional bonding adhesive, and when you run a test on these two adhesive you
see a notable noticeable difference in how they separate on impact.
So this adhesive here will absorb a lot more crash energy and it'll separate a
little bit differently. Now, these adhesives here, the panel
bonding adhesives, are mainly used for outer body panels. There's an exception
nowadays with the Ford F-150, the aluminum vehicle using 08115 on
structural panels. But other than that they are not intended for use on
structural panels. So always follow these instructions very closely, don't just
toss these aside. It's a really good idea to review these occasionally and make
sure you're following these instructions. So those are the main differences
between these two products, and really when you look at this it's pretty
obvious after these mock crash tests that there's a large difference between
the two. You've got a panel bonding adhesive that collapsed in more of an
uncontrolled manner and easier, and as you can see did not absorb the same
amount of energy as this crash toughened or impact resistant adhesive. So that's
where the science comes into this, where it's designed to absorb energy and slow
that crash event down. And you can see how much more energy this absorbed by
the way it collapsed in a much more predictable manner.
So really those are the main differences between these products. So again, follow
those OEM recommendations so you select the right product for that job.
Question number 2: When do I use 08115 bonding adhesive versus 08116? So what
are the differences? So the main difference is 08116 was specifically
designed to meet General Motors and Chrysler specifications.
And it's all about the mode of failure. In other words, for this product
GM and Chrysler wanted to see cohesive failure should the seems ever come apart
or separate, and that allows for better corrosion protection versus if you have
adhesive failure and their separation, you would only have adhesive on one side
and not on the other which, is prone to corrosion. So that's the main difference.
There is a slight difference as far as clamping time as well. There's a slightly
longer clamping time for the 08116, but the main difference again is in that
failure mode. So now, the other parts of that question is, how do I know when to
use one or the other? And obviously, we're going to follow OEM recommendations. But I
can tell you that for the 08116, Chrysler wants it used for all their
bonding operations. General Motors also specifies 08116, but only for the door
skin bonding operations. All other bonding operations for General Motors is
now recommending the structural adhesive. So those are the differences and those
are where you would use each product. But again, it all comes back to getting into
those procedures and following what the OEM says. Alright, question number 3:
Why do we need to equalize the cartridge and purge the cartridge? And the answer
is pretty simple, but we still see a lot of this not being done. So what we're
trying to do is number 1: Eliminate any air pockets that may arise inside these
plungers inside these cartridges. So by plunging the cartridge it drives the air
to the top and that'll come out in the beginning. We also need to inspect the
ports on the end of the cartridge to make sure there's nothing dried up or
hardened on the inside. It's always a good idea to have a little pick where you
can pull anything out of there that hardens up, especially once the cartridge
has been used and stored, there's a good possibility that happened.
So we need to get rid of that material as well so we have, you know, a good flow
of material going through the nozzle. Now the other question we get is, why do we
need to purge some material out after we've equalized the cartridge? And the
reason is that when this tip is empty and we're pushing product through it
there's no back pressure on the material down here. It's just air above it, so it
tends to flow through without going through that mixer very thoroughly.
So once we fill this about halfway, now there's back pressure that forces it
through that mixer a lot better. So that's why we want to just run out a
couple of inches of product before we start to apply it to the vehicle.
So I'm going to gear up here and go through that equalizing and purging procedure so
you can see what it looks like.
So you may have noticed as I extruded the product from the cartridge, that one
side came out before the other, so had we not equalized that or balanced those
cartridges, we may have had an uneven mix that may not have cured. And there's
enough adhesive in that nozzle to put out a bead quite long, where that whole
area may not properly cure. So again, emphasize that importance about
equalizing that cartridge to get a proper mix. Okay question number 4: Do
I have to remove the E-coat or galvanized coatings on the surface of
the parts? And the answer is again follow OEM recommendations. However, there's a
caveat there. Many of the OEMs will actually in their instructions state to
defer to the adhesive maker's instructions for the specific procedures
only because the OEM does not always know which adhesive you're going to
select for that particular vehicle, so the instructions may be slightly
different. So again, familiarize yourselves with these instructions. This
information is in the instructions and it'll tell you whether or not you have
to remove that coating. Now this sample here shows the difference between a
surface that just has the primers removed compared to one where it's been
abraded aggressively enough to remove all the galvanizing or zinc coating.
So you can see a drastic difference between the two. Some vehicle makers refer to
that as bright steel. They may say remove all the coatings down to bright steel. So
that means you abrade until you get that nice shiny surface and you know all the
galvanizing has been removed. But there's no simple solution and one answer.
It's always going into those procedures whether it be the OEM or the adhesive
maker's procedures to find out what they recommend as far as removing the
coatings. Now, as far as removing the E-coat, as far as the 3M 08115, 08116 and
structural adhesive are concerned, we tell you to always remove
the E-coat with one exception, and that's for 08115 and 08116 where they're
used on door skins. It's allowable to leave the OEM E-coat intact, as long as
it's scuffed and properly cleaned, but only on the door skins. So really not
very complicated, but go back to the OEM and adhesive maker's instructions for the
correct information. Okay, moving on to question number 5: Can I use heat to
accelerate the cure? As I stated earlier, because of the epoxy chemistry of these
products they handle heat very well, so it's absolutely acceptable to use heat
to force cure these products. As always, we want to observe those maximum
temperatures, so our recommendations is about 150 degrees for 40 minutes, which
will get you very close to full cure, roughly 80-85 percent of
full cure in as little as 40 minutes. So we want to observe that maximum
temperature, we don't want to abuse it and overheat, you want to monitor that
temperature closely. And it's a good idea to use something like an infrared
thermometer where you can actually get the actual temperature of the panel
rather than ambient temperature. So feel free to use heat, just follow the
instructions to do so. Okay, so question number 6 is similar to question number
5, but the question is: Can I put the product in the refrigerator to slow that
cure time down? And a simple answer is yes. However, I would recommend maybe
something a little less aggressive, like an air-conditioned office rather than
refrigerator, but as long as you're monitoring how cold it gets, you
absolutely don't want it to freeze. But just cooling that product down will give
you a little more cure time. For climates like Texas or Arizona where it gets
extremely ho,t it's not a bad idea to cool the product down some, but keep in
mind as it gets colder the viscosity gets thicker, so just take care when
you're extruding it out of the cartridge that you don't force it too hard. It may
not go through the mixer correctly and get a thorough mix. Okay, question number
7: As far as when you see equivalence in a
repair procedure, for example, it may say use 3M 08115 or equivalent. Who do I
listen to? And this is a tricky question. In order to avoid any liability issues
it's always a good idea to use the actual called-out product rather than an
equivalent. The problem with equivalence is, it takes an engineering degree to
really decipher whether it is an exact equivalent or not. It may not have
certain chemicals in it, it may have chemicals it shouldn't have in it.
So in order to say it's an exact equivalent is very difficult to say.
So simply put, I would just recommend using the adhesive that's named in that
procedure, and stay away from the equivalents as much as possible. Okay
question number 8: Why do we weld bond? And that's a great question. So, weld
bonding is the combination of adhesives and welds in the joint. Why do we need
both? Well, the adhesive adds a lot of benefits to that joint. One of the things
is it prevents corrosion because you've got a completely sealed joint that you
would not normally have with just welds. So it seals that joint to keep any
moisture or air from passing through there and causing corrosion. Another
reason is in a case of the impact resistant structural adhesive, it
actually allows the part to collapse in more of a predictable manner and absorb
energy as it collapses. Another benefit is you've got a continuous bond. Not just
a spot here and a spot there. It's continuous so you get really good lap
shear strength. The weld in there prevents the adhesive from ever going
into peel mode and starting to peel. That's kind of the weakness of any
adhesive is peel mode, and having that weld in those areas will prevent that
from happening. So a lot of benefits to combining the
welds and the adhesive together in weld bonding. Okay, number 9: Can I weld through
cured adhesive? 3M does not recommend welding through the adhesive after it's
cured. It's really important that we follow the
work time on the adhesive cartridge. In this case it says 60-minute work time.
You really want to get your welding complete within that work time. Actually
having that liquid adhesive in there helps with the conductivity
between these two panels when we're trying to spot weld through them. Once
that adhesive cures it actually acts as an insulator, almost like a gasket,
between those two pieces of metal which do not allow for that conductivity from
one side of the spot welder to the other. So the short answer is do not weld
through cured adhesives. Okay, let's wrap this up with question number 10:How do I
keep my bonded flanges from corroding? Now if we had done our replacement
procedure and our preparation perfectly, there really shouldn't be a chance of
corrosion in that joint, as long as we've got all the bare metal covered. The
adhesive has corrosion inhibitors and that should not happen. However, there's
no guarantee that during the replacement of that panel we could have maybe
damaged or scraped off some of the adhesive in certain areas. A great
example of that are quarter panels. When you hang a quarter panel, oftentimes you
need to force it a little bit down onto that wheel arch area, and in the process
of that it is possible we could scrape some of that adhesive off and leave a
void. So, insurance against that would be Cavity Wax Plus. So as long as we follow
all bonding operations with Cavity Wax Plus which will get into those areas
that might be exposed and cover them and creep, in you're not going to have that
corrosion in those joints. Also, if you read the product sheets these will tell
you: Always follow all bonding operations with Cavity Wax Plus.
Hey, I just thought of one more question so you'll get a bonus 11 questions here. this is really
important though. So the question we hear around the country is, how long will a
cartridge last after it's been opened?
And we've actually heard stories about
people saying once the cartridge has been used once
even if it's half-full or more, throw it away, it's no good. And that
really isn't true. So really the answer to that is as long as you leave the
nozzle on when you're finished with the product and allow it to harden up and
seal this cartridge, you should get very close to the original stated shelf-life.
It's also important that you know the shelf-life of these products.
It generally varies between 1 and 2 years. So as long as you seal it up
correctly, leave that nozzle on, you should get close to that 1 year or 2
year, whatever it stated, so don't just toss the product away after it's been
used once. There's still a long ways to go with it. Alright that's it, thanks
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