High-Performance Additives for Improved Water Resistance in Decorative
Coatings
Do you want to increase the water resistance of your
wood,
masonry and other porous decorative coating formulations,
but haven’t yet because of the high addition levels required
for currently available silicone products? Dow Corning® 87
Additive and Dow Corning® 88 Additive can help.
Dow Corning 87 and 88 Additives allow you to power up
your decorative coating formulations by providing improved
water resistance at addition levels as low as 2%. In addition,
both additives are solvent free and APEO-free and only
contribute <10 g/l VOCs to final paint formulations, even
when used up to 5% by weight.
The additives improve water resistance by creating a
hydrophobic silicone network in the paint that repels
water but is permeable to water vapor coming from the
substrate. As a result, water penetration is reduced while
cracking and blistering are minimized.
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Dow Corning 87 Additive is a milky white silicone resin emulsion with
low VOC contribution levels. It is designed for use in waterborne paints.
Dow Corning 88 Additive is a silane/siloxane blend with a VOC content of
73 g/l. It is effective at improving water resistance both in acrylic emulsion
paints containing polar solvents and in solvent-based systems.
Advantages of Dow Corning
87 and 88 Additives:
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Solvent-free and APEO-free
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Contribute <10 g/l VOCs when used at up to 5% by weight
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Reduce water absorption at only 2% addition by weight
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Negligible impact on water permeability, even at 5% addition by weight
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Increased contact angle for better water beading with Dow Corning 87
Additive
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Maintain paintable surfaces when used at up to 5% by weight
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Effective in waterborne acrylic and solvent-based decorative paints
Performance at Additive Levels: Reduced Water Absorption
Water absorption (W24) through a paint film is measured as a
function of time. The lower the water absorption of a coating, the more water
resistance the film offers and the greater protection it provides. Even at only
2% addition by weight, Dow Corning 87 and 88 Additives provide reduced
water absorption.
With Dow Corning 88 Additive, addition at 5% shows even further
reduction in water absorption, while a competitor silicone resin provides no
additional protection when the addition level is increased from 5% to
10%.
Figure 1: W24 of an acrylic-based emulsion paint
with and without
Dow Corning® 87 (A) and 88 (B) Additives and vs. a competitor
silicone
resin emulsion.
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The Best of Both Worlds:
Excellent Water Vapor Permeability
While Dow Corning 87 and 88 Additives reduce water absorption, they
still allow water vapor coming from the substrate to pass through the silicone
network, preventing the cracking and blistering that can be a problem with some
decorative coatings. Water vapor permeability is reported as the Sd value and
is a function of the water vapor transmission rate.
Even in a high-PVC paint formulation that has excellent water vapor
permeability, both
Dow Corning 87 Additive and Dow Corning 88 Additive have only a
minimal impact on the Sd value when used at a high addition level (Figure
2).
Figure 2:Sd of water of a high-PVC paint
formulation with and without Dow Corning® 87 (A) and 88 (B)
Additives.
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Seeing is Believing: Visual
Results Underscore Real Performance
Consumers often feel more comfortable with a product when they have visual
confirmation of its performance. When it comes to water resistance, they want
to see water beading on the coated surface. Better water beading is reflected
in a higher contact angle of water on a paint film.
Dow Corning 87 Additive shows a marked increase in contact angles in
acrylic resin formulations, even at a low addition level of 2%, and clearly
outperforms a competitor emulsion resin.
Figure 3: W24 of an acrylic-based emulsion paint
with and without
Dow Corning® 87 (A) and 88 (B) Additives and vs. a competitor silicone
resin emulsion.
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For More Information
To learn more about these products, download the
Dow Corning
87 Additive and Dow Corning
88 Additive Information Sheet.
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