Performing & Failing - SWRInstitute

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Performing & Failing
Sealants

by Patrick D. Gorman
a contractor

February 26, 2008

Thanks to the program committee for allowing me to share this information. Thanks
for your attendance. I intend that what you will take away will be factual and useful
to you.
I am a sealant application contractor. I sell no products. My bias is towards what
works and against what fails based on my research and that of scientists.

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Sealant “Facts”

• What is the best brand of
Polyurethane?

• How long do architects and
owners think sealants will
last?

• How long do applicators think
sealants will last?

For this I need your participation. Write your answer on your note paper and hold it
up for those at your table to see. Are there differing opinions?
How do you determine “best” brands? More on this later.
There is a disconnect between what architects and owners expect and we as
contractors.

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Durability

• Why do you use the products
you use?

• Is lack of callbacks a good
measure of sealant
performance?

“It’s the best” is the common answer. It’s usually a little more complicated than that.
More than likely you use products you can get from a supplier with whom you have
a relationship. For example, the urethane I use is not the best in all respects but I
can’t get the one I feel is better because the distributor provides poor service.

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Durability

Should sealants last longer for:
• Precast warehouse
• Federal courthouse
• Prison
• Structural sealant holding the

glass
If so, what would you use?

Don’t some structures call for the longest lasting sealants?
Whatever your answer, what are your resources that lead you to this conclusion?
Would anyone else using the same resources come to any different conclusion?

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“I have specialized in sealant joint design and
failure analysis for 20 years (including being
Chairman of ASTM Committee C24 on
Building Seals and Sealants for 6 years), but
I still cannot predict what will work on the
next project. We still have to perform lab and
field testing to determine the optimal joint
preparation, cleaning, primer and sealant
products. Furthermore, I see no convergence
- this situation is not improving over time. If
anything, we have more uncertainty now
than 20 years ago.”

David H. Nicastro, EDI, Jan. 2008

Consider this quotation from a respected engineer who specializes in sealants.
He’s not speaking about only the products but the substrates, the application, the
whole process.
If the engineers specializing in this field all have the same knowledge, would they all
specify the same products?
Based on Mr. Nicastro’s statement, we should all be aware that if we as contractors
are intending to improve this situation, we must be open to and involved in the
studies on the subject.

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SWR Institute,
ASTM, RILEM, ISO

• Research from these organizations
• My own ASTM published research
• Co-authoring studies with David Nicastro,

Jerome Klosowski, Victoria Demarest
• Inspection of my companies applications

since 1946

What I am presenting is a collection from research published by ASTM, RILEM,
ISO, including papers I have published and ongoing research in which I am
involved.
It includes international participation developing the SWR Institute’s applicator
training manual.
It is also based on observations and comparisons from my own company’s tests
and applications since 1946.
And the Wall.
Nobody has observed every product made. Products that I will talk about that have
been in place long enough to see performance, may not be the same as those
wearing the same name today.
Be wary of claims that a known product problem has been improved or fixed. My
experience has been that sometimes the “improvement” or “fix” created an
unanticipated problem.

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New & Facts

• What’s new:

– Extruded and pre-compressed seals
– Sylil-terminated polyether/urethanes

• Facts:

– Polysulfides are not a factor in the US now
– Silicones show longest durability
– Urethanes show shortest durability
– A huge weathering variation by brand –

particularly urethanes

Since I began studying sealants in the 70’s, not much has changed. We use the
same tools and techniques as were used 60 years ago. Application flaws still
predominate as a failure cause. Design and construction errors are equal to or a
close second to application errors. Product failures may not be any more common
now but awareness of weaker products is better known.
No single product works in every condition.

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New Studies

• Acrylics for exterior applications in high
performance applications studied

Dr. Victoria Demarest at Rohm and Haas has been doing interesting work with
acrylics since the mid 90’s and I’ve had the honor of working with her. Acrylics for
exterior use are getting some trials. We have nine buildings with several
experimental exterior acrylics in testing now for three years.
ASTM and ISO are acknowledging these products among higher performance
products. Acrylics have some characteristics that are non-intuitive. Some of what I
have learned is that though they do get harder in lower temperatures, they can be
engineered such that hardness does not necessarily directly relate to the bond line
strain. In other words, at slow rates of movement, they relax. They have
advantages like being easily tinted, paintable, water cleanup, quick to skin over and
highly UV stable.
We will report the results of our testing next month at a RILEM/ASTM symposium
and annually thereafter.

Title: Third Symposium on Durability of Building Construction Sealants and Adhesives
Dates: Wednesday June 25th 2008 - Thursday June 26th 2008
Location: Hyatt Regency Denver; Denver, CO

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ASTM Updates

• Updating weathering for movement
• Guide to define Failure with photos
• Updating “Use T”

With work from Tokyo, the UK and what Klosowski and I are doing with 4 test sites,
might result in testing of sealants WITH movement. More about this in the next
slide.
ASTM is working on a photographic guide for defining failure types. More about this
in the next slides.
Use “T” for traffic, is being revised based on our findings that design of the joint with
semi-rigid backup works best.

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Weathering Test Rack

One of the 4 weathering racks based in Michigan, Denver, Louisiana and El Paso
used to correlate laboratory testing with seasonal movement.
Many studies have proven that weathering with movement correlates better to field
conditions than the current weathering methods on the books. This study is broader
than some of those done before and uses products common in the USA. Early
indications have shown some surprises. This too will be presented in Denver on
June 25th.

Title: Third Symposium on Durability of Building Construction Sealants and Adhesives
Dates: Wednesday June 25th 2008 - Thursday June 26th 2008
Location: Hyatt Regency Denver; Denver, CO

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Sealant Failure

Define sealant failure

“I been doin’ this for 40 years and never had a callback” is my pet peeve contractor
testament. It’s an invalid way of knowing. Go look at your older applications to
really know.
Pinpointing failure causes in the field is actually quite difficult. Due to all the
variables, we are in a rather complex business.
But if you’re not looking at aged work in place, you’re missing the most telling of
information.
Is sealant failure the absence of sealant performance?

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ASTM C24 WK 11731 Guide to

Diagnosing Sealant Failure

(with permission)

• Adhesive failure • Sag

• Blooming • Weathering

• Chalking • Hardening

• Cohesive failure • Interphasal (substrate)

• Crazing • Swelling

• Dirt pickup • Compression set

• Fluid migration • Incompatibility

• Reversion • Feather edging

• Rundown

ASTM C24 WK 11731 Guide to Diagnosing Sealant Failure (with special permission)
ASTM has a committee working on a guide for diagnosing sealant failure by comparison to reference
photographs. You can participate by contributing photos to this effort (photos provided will be an
ASTM copyright).
Here are some of the definitions for which they are looking for good photos:
Adhesive failure
Blooming – movement of an ingredient to the sealant surface
Chalking – formation of a powder on a sealant surface
Cohesive failure – characterized by rupture in the sealant
Crazing -- network of fine cracks on the sealant surface
Dirt pickup –soiling caused by foreign material or organic growth in or on the sealant
Fluid migration – accumulation of a fluid from a sealant on or in adjacent material
Reversion – loss of elastomeric properties and decrease in hardness of a sealant after exposure
Rundown – fluid migration from a sealant accumulating on sloping surfaces
Sag – gravity-induced flow of a sealant on a vertical surface
Weathering – any change in a sealant due to atmospheric elements
Hardening – not defined by ASTM
Interphasal adhesion failure (e.g. EIFS or concrete patch failure of substrate)
Swelling –
Compression set (movement during cure deformation) --
Incompatibility --
Feather edging --

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Adhesive Failure

• Failure of the bond
between the sealant
and the substrate

This is the definition of the term but we contractors need to know why failure
occurred. Not an easy task.

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Chalking

Chalking – formation of a powder on a sealant surface
This is an SWR Institute Validated sealant.

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Cohesive Failure

• Characterized by
rupture within the
sealant

What are some of the causes?
Excessive movement
Thin sealant
Movement during cure changed the geometry
Critter attack or vandalism
UV scission causing cracks to burn through

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Crazing

A network of fine cracks
on the sealant surface

Crazing -- network of fine cracks on the sealant surface
Crazing is a time and exposure related process. Depending on the formulation, it
can be slight or very deep.

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Dirt Pick-up

Soiling caused by foreign
material or organic growth
in or on the sealant

Dirt pickup –soiling caused by foreign material or organic growth in or on the sealant

Most sealants pick up dirt.

Those that chalk, slough off dirt with age.

In my studies with Klosowski that are 3 years in, they show lots of organic growth in
the Louisiana samples compared to those in my desert climate. With little rain, we
see dirt accumulation.

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Fluid Migration

Accumulation of a fluid from a
sealant on or in adjacent material

Fluid migration – accumulation of a fluid from a sealant on or in adjacent material
This can be a disastrous failure. Happens with all types of sealants.

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Reversion

Reversion – loss of elastomeric properties and decrease in hardness of a sealant
after exposure
These types of failures are familiar to most of us. I have seen it in urethanes,
acrylics and sylil-terminated urethanes. Heat, moisture or UV light in combination or
individually can cause reversion.

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Hardening

Not defined by ASTM. Some products harden substantially with age and exposure.

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Interphasal Failure
(substrate failure)

Interphasal adhesion failure or substrate failure (e.g. EIFS or concrete patch failure
of substrate)
Though commonly thought of related mostly to EIFS, it occurs elsewhere, such as
on painted substrates or weak concrete (often at patched joints).

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Stain or Dirt Rundown?

Rundown – fluid migration from a sealant accumulating on sloping surfaces
Often confused with simple dirt residue from light rains washing streaks onto
surfaces below.
In the lower left is what appears to be cleaned window ledges from concentrated
water flow from the windows.
Very difficult to determine if it is actually a result of fluids leaching out of the sealant
creating a water repellent.

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Compatibility

This is a white silicone applied directly over asphalt impregnated form filler between
concrete pours. Yet, it does not affect the performance of the sealant other than the
discoloration which was defined as failure by this architect.

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Compression Set

Compression set (movement during cure deformation)
Combining a slow curing sealant in a high or rapidly moving joint is where
compression set usually occurs.
Parking garage joints or long runs of PVC or aluminum are common places to
expect this failure.
As a point of interest, PVC moves thermodynamically 2 to 3 times more than
aluminum.
Counter intuitively, compression is more damaging to joint sealants than extension.
Thus winter installations may be at greater risk of damage.
Remember, until the sealant in contact with the backup material is cured, it sticks to
the backup material – a form of 3-sided adhesion.

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Temperature Change 820F

Joint movement is mostly related to temperature change during the life of the
sealant. It must consider surface temperatures of south facing dark colored
substrates and many other factors.
In my area, 30 degree daily temperature changes are common and 40 degree
changes happen occasionally. But during the life of a sealant, as much as 150
degrees change has been measured on a black aluminum surface (low of 10 to a
high of 160).
Most urethane sealants have upper temperature limits of 140 to 160 degrees before
they cook. Not uncommon temperatures on black aluminum in the southwest.

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Application Failure

• Decision to seal a joint that can’t work
• Joint preparation
• Tooling (or lack thereof)
• Geometry
• Primer errors
• Mixing errors
• Inadequate “bite”
• Bond breaker (out-gassing, adhesion, etc.)

I am sure you can add to this list. Any ideas?
It’s all about getting the liquid sealant to stick to the substrate and achieving a
properly cured geometry.
The best sealant improperly applied won’t work, and visa versa.
In the winter in my climate, some single component sealants (acrylics and silicones)
take a month to cure.
One comprehensive study in Europe showed 55% of joints failed within less than 10
years of service life. 90% of the joints properly installed lasted more than 20 years.

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Sealing an Impossible Condition

EIFS substrate is foam

No substrate “bite”

Perimeter joints in window cladding have been found to be failed most frequently in
several studies.
The condition depicted is not that uncommon.
The applicator who decides to try to seal this joint is not making good choices.
Window installers are the annuity for restoration sealant applicators. Your future is
good and getting better with every window being put in.

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Sealing an Impossible Condition

Aggregate faced precast in which the aggregate is exposed at the bond line doesn’t
work.

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Primer Errors

• Primers enhance adhesion
• They can reduce moisture at bond line
• Always test primers first

There was an interesting study by Kinney & Assoc. published by ASTM showing
that sometimes the best primer did not come from that sealant’s manufacturer.
Another study showed primers almost always enhance adhesion.

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Bond Breakers

• Test bond breakers

– Primed
– Unprimed
– Different sealants

You may be surprised if you run a test like this on your bond breakers. Here are 6
unprimed sealants and 5 common bond breakers.
All 6 stuck to a skin of the styrofoam.
The Dow 790 was the only one to stick to the strapping tape.
Sonolastic 150 and Dow 790 stuck to the black polyethylene tape.
Sonneborn NP1 and Dow 790 and 795 stuck to the polyethylene backing material.
Nothing stuck to the wax crayon but the Dynatrol II almost did.
These are not the exact same results had primer gotten onto the backing.

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Proper Backup?

Backup materials found listed from the left:
None
Braded neoprene with polysulfide and a skim coat of urethane
Rows of neoprene rod
Newspaper
Boxer shorts
Stretched backer retracted where two pieces joined the evening of application
causing a break in the sealant as it pulled apart

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Geometry

Applied sealant geometry is important and not as easy to accomplish as the typical
applicator thinks.
In our study of over 220 installations, geometry varied greatly.
Within a 20’ joint the depth variation is often great.

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Top line is joint width.
Blue line is sealant thickness.
This graph plots variations in an applied joint from 1 ¼ ” deep in a ¾” wide joint to
¼” deep in a 1” wide joint.
Tooling tends to focus on aesthetics. Once well tooled, a joint may look good but
hide geometry that can’t work.
The best training for an applicator is to learn how to do a wet depth check to verify
proper application.

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Geometry

If the joint has little or no movement, these silly seals actually work.
This fact confuses some to think if they had no failure, it was done right.

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Geometry

Only those that had movement among these failed.

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Physical Damage Failure

• High heels
• Vandalism (schools, prison, smoker’s

areas)
• Animal attack (e. g. birds, ants, etc.)
• Chemical attack
• Immersion swelling
• Cycling fatigue

Narrow high heels puncture sealants easily.
They are subject to direct UV, constant moisture, frequent water blasting and
movement.

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High Heel Damage

Some years ago, I reported testing Nicastro & I did for ASTM and ISO that resulted
in changes in “Use T” for pedestrian traffic joints. The effort continues and so far
the results are:
•Sealant hardness is not the determining factor since both soft and hard sealants
proved they could work
•Hardness of the backup material was the determining factor in heel impact survival
•A pre-compressed foam seal as backup worked best
•Joint design including a relative hard backup worked better than any sealant alone
•Hard backup material and hard sealants accommodate little movement, thus
designing more joints experiencing less movement helps though exposing more
area to damage
High, rapid moving joints deform slow curing sealants

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Product Failure

• Hardening • Reversion
• Shrinkage • Cure (too slow or none)
• Color change • Dirt pickup
• Adhesive loss • Staining
• Tear propagation

UV sunlight causes more sealant damage than anything else I see. This has been
confirmed in world wide studies.

We spend a lot of time on movement and adhesion while little has been done about
aesthetics as sealants age.

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How Do You Know

Where do you get objective, accurate

information about sealants?
• Data sheets
• Architect
• Manufacturer reps for the substrate or

sealant
• SWRI network
• Reviewing your old applications
• Research as in ASTM

If you are relying on the top three choices, you might be missing something.
Looking at your applications after years of service is your best resource.
Talk to SWR Institute members who have a practice of looking at aged installations.
When asking SWR Institute members what is working, be sure to ask how the
answer was derived.
Remember, no call-backs is an invalid way of knowing.
So is the statement that tons of the stuff has been sold all over for years.
There is a lot of available research available from organizations such as ASTM.

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Joint Movement Indicators

This has been called the “lie detector.”
In any question of how much movement a joint is experiencing, this simple, cheap
device tells the indisputable truth.
Measurements of the scratch can be interpolated over the anticipated lifetime
temperature change.
In this photo, we found not only excessive movement but it was also in shear.
Notice the joint size in relation to the movement.
This joint shows movement of 100% of the joint width in one month.

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The Wall

This simple idea came from Jerry Klosowski at an SWR Institute meeting many
years ago. It simply shows how sealants hold up in your environment without
movement.
We started just applying commonly used products on the south facing metal wall. It
was an eye opener for us.
For example, the Sonneborn NP2 on the right was applied in February of 2000.
The sample on the right was very thin and reverted with heat.
The sample to the left is holding up very well for 8 years, though crazed and
reverted at the thin feathered edges.

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The Wall

Here (left photo) we applied three flavors of a sylil-terminated-polyurethane. The
one on the left is a single component and picked up some dirt.
The one in the middle is also a gray but a 2-part and picked up a huge amount of
dirt and is reverting.
The white on the right, is also a single component and chalked heavily so it picked
up no dirt.
In two, the rubber still looks good after 8 years.
The urethane on the right is a white single component that picked up more dirt than
anything on the wall and plasticizer migrated a half inch onto the metal.

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Pecora AVW 920 placed Mar. ’00
Mar. ‘00 & Feb. ‘08

This acrylic looks quite good and is flexible after 8 years even though the sample
was put on very thin.

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Geocel 945 placed Nov. ‘03
Feb. ’04 – Feb. ‘08

One of the best looking urethanes on the wall so far (only 4 years in place).

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STPU placed June ‘01
Feb. ’04 – Feb. ‘08

The fact that the one on the right is looks cleaner at 4 years older than the dark one
on the left is probably because the plasticizers that saturated the dirt on the left has
begun to burn off.

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LymTal 100 placed Mar. ’96
Feb. ’04 – Feb. ‘08

This reverted early on.

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Pecora 865 placed June ’00
June ’00 – Feb. ‘08

Silicones on the wall show little age. Some pick up dirt and some don’t.

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Sika 15LM placed Aug. ’00
Feb. ’04 – Feb. ‘08

Though applied thin, this product is showing crazing.

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