Transcript Presentation_Slides

Practical Applications
of Polysiloxane Coatings
Gerald L. Witucki
August 2013
Agenda
• Evolution of protective coatings and
need for amine-functional siloxanes
• Features and benefits
• Performance testing
• Market information
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Evolution of Protective Coatings
• Coatings protect substrates from environmental degradation
• Prior to 1990s, typically based on organic binders (e.g., epoxy or polyurethane)
• Interest in siloxane technologies is expanding; anticipated (U.S.) AGR: 12%*
Binders Used in Coatings
U.S. Patents Issued for
Polysiloxane-Epoxy Hybrid Coatings Per Year
Silicones 1.4%
*KNG
2006-2011 Industry Report
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‘Polysiloxane’ Coatings
Technology
• Broadly, polysiloxane = silicone
• In the coatings industry, polysiloxane
refers to silicone-organic resin hybrids
– Best known are silicone-epoxy and
silicone-acrylate systems
• Viewed as premium topcoats
• Over the last two decades,
“polysiloxane” technology has facilitated
a shift from three-coat to two-coat
systems, reducing labor costs and
downtime while improving weathering
performance
4
Two Coats vs. Three Coats
5 mils
Urethane
Topcoat
3-5 mils
Polysiloxane
Hybrid
Epoxy
Basecoat
5 mils
Zinc Primer
Zinc Primer
Steel
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‘Polysiloxane’ Coatings
Technology: State-of-the-Art
• Includes organic resin, methoxyfunctional silicone resin and an
amino-functional silane
• The silane acts as a bridge between
the two resins; the amine group
reacts with the functional group on
the organic, and the alkoxy groups
co-hydrolyze and condense with the
silicone
6
Cure Mechanism of SilaneBased Polysiloxane Coatings
Ameron 1981 Patent: US5618860A
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Limitations of Silane-Based
Polysiloxanes
Feature
Limitation
Rely on moisture for hydrolysis and temperature
for condensation
Proper cure is dependent on application conditions
Alkoxy reaction leads to reduced coating mass on
the substrate
Causes film stress (cracking and adhesion loss)
Residual alkoxy groups can continue to react after
the coating appears fully cured (post-cure drift)
Can result in film embrittlement
Alcohol is an undesirable by-product of alkoxyfunctional intermediates
This contributes to VOC of the formulation;
methanol can create labeling issues due to toxicity
For polysiloxane technology to proliferate in the
market, this must move beyond alkoxy cure
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Beyond Alkoxy Silane Cure
• Siloxanes are polymerized silanes
 Polymer structure achieved prior to application
 Not reliant on ambient conditions to achieve cure
 No generation of alcohol during film cure
Compatibility of the siloxane with
organics and the level of crosslinking
can be “dialed-in” to achieve specific
performance requirements
9
Utility of Organofunctional
Groups in Resin Chemistries
Resin
Systems
Carbinol
Urethane
n
Epoxy
n
Polyester
Phenol
n
Aldehyde
n
Amino
Isocyanate
n
n
Epoxy
n
n
n
n
n
Alkyd
n
n
Amine
n
Acrylic
n
n
Carboxy
n
n
n
Acrylate
n
n
n
n
Dow Corning has chosen amine functionality to
offer a broad utility in coatings resin chemistries
10
Cure Chemistry of
Silicone Amine Resin
• No tin or titanate
catalysts
• No reliance on ambient
moisture
• No alcohol by-product
11
Silicone Amine Resin
Typical Properties
•
•
•
•
Viscosity at 25ºC (77ºF): 2,500-5,000 cSt
Amine equivalent weight: 250-270 grams/NH
Nonvolatile effective content: >97%*
Appearance: clear and water-white to light straw
*When reacted with organic resin
12
Differentiated Performance
of Silicone Amine Resin
Feature
<1% residual solvent, amine-functional silicone
resin
Benefit
Formulate to lower VOC regulations
Offers improved chemical, weathering, thermal and Higher level of coating performance and durability
corrosion resistance over traditional epoxy
coatings
Comparable physical properties to two-component
polyurethane, but with better corrosion resistance
Potential to replace the three-coat system with a
two-coat system for labor cost and downtime
reduction
Potential utility in other coatings applications and
new markets
Can use anywhere that amine functionality is
utilized
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Benefits of
Silicone Amine Resin
Silicone Amine
Resin
Competitive
Amino Si Resin
Alkoxy
Silane-Based
Polysiloxane
Two-Component
Polyurethane
Solvent content
<1%
10%
<1%
25%*
Post-cure drift
potential
Low
Low
High
None
HAPS content
No
Yes (xylene)
No
No
Isocyanate hazard
No
No
No
Yes
Methanol hazard
No
No
Yes
No
Application coats
Primer/top
Primer/top
Primer/top
Primer/base/top
*As supplied
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Performance Testing
• Cycloaliphatic epoxy resin crosslinked with silicone amine resin
• Pigmented with TiO2 (0.8 pigment: binder)
• Compared against:
–
–
–
–
Silane-based polysiloxane
Organic polyamine crosslinker
Polyurethane acrylic
Also evaluated additions of
alkoxy-functional siloxane and
hindered amine light stabilizer
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Circular Dry Time
Circular Dry Time, hr
Set to Touch
Surface Dry
Through
Dry
Silicone amine resin/organic amine (15% Si)
4
6
7.5
Silicone amine resin/organic amine (30% Si)
2.5
4.25
8
3
5
7
Organic amine (0% Si)
3.5
5
7.5
Amino silane (23% Si)
1
6
16
Silicone amine resin/silane (44% Si)
2.5
4
6.5
Alkoxy silicone/silane (56% Si)
1
3.5
5
Silicone amine resin/alkoxy silicone (70% Si)
2
5.5
7
2K PU (0% Si)
3
9.5
14
Silicone amine resin (56% Si)
• Epoxy-based coatings provide overall faster dry times versus polyurethane
chemistry
• Silicone amine resin cure is comparable to organic crosslinker
• The alkoxy silane-based polysiloxane cured fastest (at ambient lab conditions)
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Film Properties
MEK
Pendulum
Pendulum
MEK
Mandrel Resistance,
Hardness
Hardness Resistance
Flexibility, dbl rubs
Silicone amine resin/organic amine (15% Si)
Silicone amine resin/organic amine (15% Si)
114
Silicone amine resin/organic amine (30%106
Si)
Silicone amine resin/organic amine (30% Si)
, dbl rubs
114 inches
>300
1/4
250
1/4
106
Mandrel
Flexibility,
inches
>300
1/4
250
1/4
Silicone
amine
Si)
Silicone amine
resinresin
(56% (56%
Si)
85
135 85
3/16
135
3/16
Organic
amine
Organic amine
(0% (0%
Si) Si)
103
>300103
3/16
>300
3/16
Amino silane
(23%
Si) Si)
Amino
silane
(23%
28
1/4
125
1/4
Silicone amine resin/silane (44% Si)
Silicone
amine resin/silane (44% Si)
64
125 28
80
1/4
80
1/4
Alkoxy silicone/silane (56% Si)
94
155
5/16
Silicone amine resin/alkoxy silicone (70% Si)
78
37
155
5/16
37
3/16
>300
<1/8
Alkoxy silicone/silane (56% Si)
Silicone
amine resin/alkoxy silicone (70%129
Si)
PU (0% Si)
PU (0% Si)
64
94
>300
78
3/16
<1/8
129
The paints were all comparable in terms of gloss, but
the epoxy-containing formulations outperformed the
polyurethane in terms of distinctness of image (DOI)
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Chemical Resistance
#
Chemical
1
Acetic acid (10%)
2
Formic acid (10%)
3
Hydrochloric acid (36%)
4
Nitric acid (50%)
5
Phosphoric acid (50%)
6
Sulfuric acid (50%)
7
Ammonium hydroxide (20%)
8
Potassium hydroxide (20%)
9
Sodium hydroxide (20%)
Epoxy +
Silicone Amine Resin
Epoxy +
Organic Amine
Five drops of chemical; covered with watch
glass for 24 hours
Adding silicone amine resin improves the
chemical resistance beyond that of a traditional
epoxy coating
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UV Durability
20° GLOSS AFTER QUV-A EXPOSURE
• Silicone amine resin outperforms state-of-the-art polysiloxane
• Increasing the percentage of silicone provides performance comparable to PU
19
Outdoor Weather Resistance
20° GLOSS AFTER OUTDOOR MICHIGAN EXPOSURE
Silicone amine resin yellowing:
comparable to state-of-the-art polysiloxane
20
Flexibility After Weathering
Mandrel Bend Rating,
inches
%Si
After 10
Days
One Year
Outdoors
Alkoxy silane-based
polysiloxane
50
>1
5
Epoxy + silicone amine
resin
50
1
1
After one year of outdoor exposure, silicone
amine resin paint retains flexibility
4-inch
mandrel bend –
silane-based
polysiloxane
1-inch
mandrel
bend – with
silicone amine
resin
21
Water Absorption
CYCLOALIPHATIC EPOXY (%WT GAIN)
Water absorption decreases
with higher use of
silicone amine resin
BPA EPOXY RESIN (%WT GAIN)
22
Thermal Stability Performance
THERMAL STABILITY WITH A CYCLOALIPHATIC EPOXY
• Thermogravimetric analysis
(TGA) measures weight loss at
time and temperature
THERMAL STABILITY WITH A BPA EPOXY
Silicone amine resin
reduces thermal
degradation
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Corrosion Resistance
• Cycloaliphatic epoxy paint
• Spray-applied
• Ground cold-rolled steel panels
• 1,500 hours salt spray (scribed)
Scribe
Creep,
mm
Silicone amine resin/organic amine
(50% Si)
55
Silicone amine resin/alkoxy silicone
(60% Si)
48
Silicone amine resin/alkoxy silicone
(70% Si)
37
Epoxy (with organic amine)
57
Two-component polyurethane
67
Increased Si content improves
corrosion resistance
24
Solvent Solubility of
Silicone Amine Resin
• Checked at 10, 50 and 90% NVC in various solvents
• Acceptable: alcohols and aromatics
– Ester alcohol, methanol, butanol, 2-propanol, EEP, PCBTF,
xylene, toluene
• Unacceptable: aliphatics, acetates
– Ethylene glycol, ethylene glycol butyl ether (color), heptane,
mineral spirit (OK as diluent), Aromatic 150 (color)
• Ketones are good solvents for silicone resins, but they react with
amines to form ketimines, which will not react with epoxies until
hydrolyzed
25
Example Formulations
White Gloss Topcoat – Ingredients
% Silicone
50
60
70
Cycloaliphatic epoxy resin
25.68
22.03
16.50
Silicone amine resin (5% xs NH)
27.58
28.86
21.62
Organic polyamine
1.75
4.09
16.82
43.99
43.95
Dibutyltin dilaurate
0.01
0.03
Tetrabutyltitanate
0.02
0.08
0.97
0.99
0.99
100
100
100
Alkoxy silicone resin
Rutile TiO2
Hindered amine light stabilizer
44.01
Xylene as needed
Silicone amine resin may be blended with other Si
resins or organic resins to customize performance
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Other Formulating Options
• Performance can be boosted with the inclusion of additional
siloxane resins (above that dictated by amine stoichiometry)
• Acrylates can reduce dry-to-touch time by reacting quickly with the
amines via Michael addition
• The addition of ketones such as methylisobutylketone (MIBK) to
silicone amine resin can extend pot life by reacting with the amine
groups to form ketimines
• Reaction time is dependent upon amine-epoxy concentration, so
increasing the functionality will speed cure
• Tertiary amines and polyols are known to accelerate the amineepoxy reaction
• Compatible with low-viscosity novolac resins
27
Conclusions
 Amine functionality provides potential utility in a broad range of
chemistries
 Allows for low-VOC formulating
 Cure chemistry eliminates mass loss, stress cracking and postcure drift
 Silicone amine resin improves epoxy coatings’ resistance to
chemical, thermal, UV and moisture attack
 Comparable physical properties to two-component
polyurethane, but with better corrosion resistance
– Allows for replacing three-coat system with two-coat
(primer/topcoat) system for labor cost and downtime reduction
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Amino Resin Coatings
Applications*
•
•
•
•
•
•
•
•
•
•
•
•
•
Industrial/protective coatings
Water/wastewater facilities
Metal containers
Coil
Wood furniture
Metal furniture
Prefinished wood
Appliances
Machinery & equipment
Electrical insulation
Automotive
Land transportation
General metal & misc. OEM
Potential utility may be found where improved
properties of flexibility, weathering, corrosion,
water and heat resistance are needed
*KNG 2006-2011 Industry Report
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Potential Beyond Traditional
Protective Coatings
• Amine functionality offers potential
opportunities in a wide range of
applications and chemistries:
– Fire-resistant and intumescent
coatings
– Composite polymers
– Industrial adhesives
– High-temperature coatings
Anywhere amine polymers are used
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Learn More About
Dow Corning® 3055 Resin
• Visit dowcorning.com/coatings for technical
data sheets, informational brochures and more
information on Dow Corning® brand products
• Look for our 10-part series on YouTube;
Search for “3055 Resin” and learn how
Dow Corning® 3055 Resin can help you
formulate durable protective coatings
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For More Information
• For more information or to order samples, contact your local
Univar representative, or:
– Email [email protected]
– Visit univarusa.com
– Call +1-708-325-2444
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Q&A
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The formulations described on slide 26 represent potential use of Dow Corning material and are not commercialized products.
Dow Corning believes that the information and data on which these formulations are based are reliable, but have not been
subjected to extensive testing for performance, efficacy or safety. In addition, Dow Corning has not undertaken a comprehensive
patent search on the formulations. Suggestions of uses should not be taken as inducements to infringe any particular patent.
BEFORE COMMERCIALIZATION, YOU SHOULD THOROUGHLY TEST THE FORMULATION OR ANY VARIATION OF IT TO
DETERMINE ITS PERFORMANCE, EFFICACY AND SAFETY. IT IS YOUR RESPONSIBILITY TO OBTAIN ANY NECESSARY
GOVERNMENT CLEARANCE, LICENSE OR REGISTRATION.
The information provided in this presentation does not constitute a contractual commitment by Dow Corning. While Dow Corning
does its best to assure that information contained in this presentation is accurate and fully up-to-date, Dow Corning does not
guarantee or warranty the accuracy or completeness of information provided in this presentation. Dow Corning reserves the right
to make improvements, corrections and/or changes to this presentation in the future.
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