MIL-HDBK-1110
pigment particles and bond them to the substrate. This may
result in a poorly bonded or porous film or one with a mottled
appearance.
2.1.4
Other Components. There are also many additives used
in small amounts in coatings to provide some special function.
These include antifoam agents, flattening agents to reduce gloss,
mildewcides, adhesion promoters, viscosity modifiers, and
ultraviolet stabilizers.
2.1.5
Spreading Rate. If the percent solids by volume of a
coating is known, the dry film thickness of a coating can be
determined from its wet film thickness by the relationship:
Dry Film
Thickness = Wet Film Thickness x Percent Solids by Volume
100
Also, it can be shown mathematically that if 1 gallon
of coating is uniformly applied to a flat surface at 1 mil (0.001
inch) wet film thickness, it will cover an area of 1600 square
feet. Thus, if the percent solids by volume of a paint is
provided by the supplier, its spreading rate at any dry film
thickness (dft) can be determined, as shown below:
a)
0 Percent Solvent - 1600 square feet at 1-mil dft
(100 Percent Solids) 800 square feet at 2-mil dft
400 square feet at 4-mil dft
b)
50 Percent Solvent -
600 square feet at 1-mil dft
(50 Percent Solids)
400 square feet at 2-mil dft
by volume
200 square feet at 4-mil dft
Obviously, this relationship is only true for coatings
as received from the supplier without thinning. Thinning will
reduce the percent solids by volume reported by the supplier and
require calculating a new value before the above relationship can
be used.
2.2
Mechanisms of Curing of Coatings.
Coatings cure from
one of three basic ways:
a)
Air oxidation (polymerization) of unsaturated
drying oils
b)
Evaporation of solvent from lacquers or water from
c) Chemical reaction of components or chemical
reaction with water in air
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