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 2

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 3

‘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 Polysiloxane Hybrid Zinc Primer Steel Urethane Topcoat Epoxy Basecoat Zinc Primer 3-5 mils 5 mils 5

‘Polysiloxane’ Coatings Technology: State-of-the-Art

• Includes organic resin, methoxy functional 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 Silane Based Polysiloxane Coatings

Ameron 1981 Patent: US5618860A 7

Limitations of Silane-Based Polysiloxanes

Feature

Rely on moisture for hydrolysis and temperature for condensation

Limitation

Proper cure is dependent on application conditions Alkoxy reaction leads to reduced coating mass on the substrate Residual alkoxy groups can continue to react after the coating appears fully cured (post-cure drift) Alcohol is an undesirable by-product of alkoxy functional intermediates Causes film stress (cracking and adhesion loss) Can result in film embrittlement 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 8

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

Urethane Epoxy Polyester Alkyd Amine Acrylic

Carbinol

n n n n n n

Phenol

n

Aldehyde

n n

Amino

n n n n n n

Isocyanate

n

Epoxy Carboxy Acrylate

n n n 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 Benefit

<1% residual solvent, amine-functional silicone resin Offers improved chemical, weathering, thermal and corrosion resistance over traditional epoxy coatings Higher level of coating performance and durability Comparable physical properties to two-component polyurethane, but with better corrosion resistance Potential utility in other coatings applications and new markets Formulate to lower VOC regulations Potential to replace the three-coat system with a two-coat system for labor cost and downtime reduction Can use anywhere that amine functionality is utilized 13

Benefits of Silicone Amine Resin

Solvent content Post-cure drift potential HAPS content Isocyanate hazard Methanol hazard Application coats *As supplied

Silicone Amine Resin Competitive Amino Si Resin

<1% Low No No No Primer/top 10% Low Yes (xylene) No No Primer/top

Alkoxy Silane-Based Polysiloxane

<1% High No No Yes Primer/top

Two-Component Polyurethane

25% * None No Yes No Primer/base/top 14

Performance Testing

• Cycloaliphatic epoxy resin crosslinked with silicone amine resin • Pigmented with TiO 2 • Compared against: (0.8 pigment: binder) – Silane-based polysiloxane – Organic polyamine crosslinker – Polyurethane acrylic – Also evaluated additions of alkoxy-functional siloxane and hindered amine light stabilizer 15

Circular Dry Time

Silicone amine resin/organic amine (15% Si) Silicone amine resin/organic amine (30% Si) Silicone amine resin (56% Si) Organic amine (0% Si) Amino silane (23% Si) Silicone amine resin/silane (44% Si) Alkoxy silicone/silane (56% Si) Silicone amine resin/alkoxy silicone (70% Si) 2K PU (0% Si)

Set to Touch

4 2.5

3 3.5

1 2.5

1 2 3

Circular Dry Time, hr Surface Dry

6 4.25

5 5 6 4 3.5

5.5

9.5

Through Dry

7.5

8 7 7.5

16 6.5

5 7 14 • 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) 16

Film Properties

Silicone amine resin/organic amine (15% Si) Silicone amine resin/organic amine (15% Si)

Pendulum Hardness

114 Silicone amine resin/organic amine (30% Si) Silicone amine resin/organic amine (30% Si) 85

Pendulum Hardness Resistance , dbl rubs

>300 250 114 106

Mandrel Flexibility, inches

1/4 1/4

MEK Resistance, dbl rubs

>300 250 135 85 3/16 135 103 >300 103 3/16 >300 28 64 Alkoxy silicone/silane (56% Si) Alkoxy silicone/silane (56% Si) Silicone amine resin/alkoxy silicone (70% Si) PU (0% Si) 94 78 PU (0% Si) 125 28 80 64 155 94 37 >300 78 129 1/4 1/4 5/16 3/16 <1/8 125 80 155 37 >300

Mandrel Flexibility, inches

1/4 1/4 3/16 3/16 1/4 1/4 5/16 3/16 <1/8 The paints were all comparable in terms of gloss, but the epoxy-containing formulations outperformed the polyurethane in terms of distinctness of image (DOI) 17

Chemical Resistance

#

6 7 8 9 1 2 3 4 5

Chemical

Acetic acid (10%) Formic acid (10%) Hydrochloric acid (36%) Nitric acid (50%) Phosphoric acid (50%) Sulfuric acid (50%) Ammonium hydroxide (20%) Potassium hydroxide (20%) Sodium hydroxide (20%)

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

Epoxy + Silicone Amine Resin Epoxy + Organic Amine

18

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

Alkoxy silane-based polysiloxane Epoxy + silicone amine resin

%Si

50 50

Mandrel Bend Rating, inches After 10 Days One Year Outdoors

>1 5 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) BPA EPOXY RESIN (%WT GAIN) Water absorption decreases with higher use of silicone amine resin 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 23

Corrosion Resistance

• Cycloaliphatic epoxy paint • Spray-applied • Ground cold-rolled steel panels • 1,500 hours salt spray (scribed)

Scribe Creep, mm

55 Silicone amine resin/organic amine (50% Si) Silicone amine resin/alkoxy silicone (60% Si) Silicone amine resin/alkoxy silicone (70% Si) Epoxy (with organic amine) Two-component polyurethane 48 37 57 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

Cycloaliphatic epoxy resin Silicone amine resin (5% xs NH) Organic polyamine Alkoxy silicone resin Rutile TiO 2 Dibutyltin dilaurate Tetrabutyltitanate Hindered amine light stabilizer Xylene as needed

50

25.68

27.58

1.75

44.01

0.97

100

% Silicone 60

22.03

28.86

4.09

43.99

0.01

0.02

0.99

100

70

16.50

21.62

16.82

43.95

0.03

0.08

0.99

100 Silicone amine resin may be blended with other Si resins or organic resins to customize performance 26

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 amine epoxy reaction • Compatible with low-viscosity novolac resins 27

Conclusions

   Allows for low-VOC formulating Cure chemistry eliminates mass loss, stress cracking and post cure drift  Amine functionality provides potential utility in a broad range of chemistries 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 28

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 29

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 30

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 31

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 32

Q & A

33

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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