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Based
on liquid resins of low viscosity. They are used
where the presence of solvent is undesirable, for
example, in tank interiors and other enclosed spaces.
These
high build paints are formulated to cure either
by chemical reaction (two pack types such as epoxies
or polyurethane), or are non-convertible types (high
build vinyl or chlorinated rubber), which dry, solely
by solvent evaporation.
With
oxidizable media, such as alkyds or oleo resinous
types, there is a limit to the film thickness, which
can be applied in one operation. Oxygen is required
for cure, and must be available throughout the film
until it is dry and hard. With thick films, oxidation
of the surface layers produces a “skin”,
which reduces the rate of oxygen penetration to
the lower layers. These can remain soft for a consideration
time. Very thick films should contain a minimum
of solvent. |
