EXPERT ADVICE
Rheological
Additives
For Sealcoatings
By Girish C. Dubey, President STAR, INC.
heology is the property that deals
with the flow behavior of a coating
during the manufacturing and ap-
plication process. The very basic re-
quirement for a coating to perform ade-
quately is to flow evenly and cover the
substrate evenly. This requirement is,
however, different for different products.
For example, a house paint should be
thick enough to be loaded sufficiently on
a brush or roller yet have the ability to thin
down and flow evenly, when the brush or
roller is pushed on the surface. If the paint
is too thin or thick the application will be
poor and performance unacceptable. Sim-
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ilarly, Sealcoating products must have
proper rheology to function as pavement
coatings. They shall be thick enough to
hold sand/aggregates in suspension, yet
fluid enough to flow into the pavement
profile and covering squeegee or brush
marks. This is the essence of Rheology.
RHEOLOGICAL ADDITIVES
The use of rheological additives in seal-
coating formulations is essential. They are
known by different names; thickeners,
rheology modifiers, bodying agents etc. In
Sealcoatings, several rheological additives
are used which vary in their effectiveness
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for rheology modification as well as their
effect on the overall performance of the
cured sealcoating. Let us review these ad-
ditives in the light of their performance
as rheology control agents, strengths and
weaknesses.
1. SALTS
Chemical compounds e.g. sodium sul-
fate, magnesium chloride, acetic acid etc.
have been used in sealcoatings where they
have been observed to produce instanta-
neous thickening. The thickening effect is
derived from the fact that these chemicals
ionize in water to produce acidity which
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