TM 5-805 - 6
Figure 8. Preformed Sealant at Ceiling to Wall Joint
joint tillers because they are tacky enough to
temperatures ranging from -40 to 145 degrees C
produce a seal but have little true adhesion and
(-40 to +275 degrees F). Dry foam is available
little recovery after being deformed. Non-resilient
with an adhesive to hold the sealant in place
tapes are used for hidden joints, often with a cap
during application.
bead of a compatible sealant. These sealants
should not be used in working joints or in visible
use of sealants in acoustical applications. An
exterior joints.
acoustical sealant can be almost any sealant that
(2) Resilient tapes, beads, and gaskets. These
maintains sufficient adhesion and cohesion to hold
resilient materials are generally made of cured
it in place, keep it from falling apart, and block
butyl, polyisobutene, or other synthetic rubber and
the path of sound. The prevention of air penetra-
fillers. They stay tacky, are harder than non-
tion is more critical to sound attenuation than the
resilient tapes, and have greater recovery after
actual sound deadening of the sealant itself. Non-
deformation. Resilient gaskets are used for seals in
skinning sealants are most often used because
glazing and exterior panels and as structural
they are least expensive. Following are acoustic
gaskets.
considerations for various types of sealants, which,
j. Wool felt. This sealant is a wool felt impreg-
except for the "non-skinning," are described in
nated with a non-hardening anti-corrosive com-
more detail elsewhere in this manual.
pound. Wool felt sealant is brown in color, is not
(1) Non-skinning sealants. These sealants re-
affected by heat below its ignition temperature,
main soft and pliable because of their butyl,
and is available with adhesive on one side.
polybutene, or polyisobutylene polymer base. They
k. Resilient foam. These sealants are preformed
are gun-grade, non-curing, ready for immediate
polyurethane foam strips that are waterproofed
use, can be applied at temperatures ranging from
with a coating such as asphalt or polybutylene. To
-18 to +38 degrees C (0 to 100 degrees F), and
be effective, the sealants must be used under
will stand service temperatures ranging from -52
compression. The percentage of compression deter-
to +93 degrees C (-60 to 200 degrees F).
mines the joint's capacity and varies with the
Non-skinning sealants are used in fixed joints
sealant's manufacturer. For example, to weather-
between metals and glass and may be capped with
proof a joint, one sealant may have to be com-
a bead of compatible elastomeric sealant. Non-
pressed 75 percent while another material may be
skinning sealants may stain porous surfaces and
effective when compressed 50 percent. The service
should not be used on exposed masonry. They are
temperature of resilient foam is limited by the
subject to attack by petroleum products; do not
waterproofing material and ranges from -40 to +
provide a good base for paint, and may retain dirt.
93 degrees C (-40 to + 200 degrees F). Polyure-
While recommended only for use in fixed (non-
thane foam without waterproofing can be used in
moving) hidden joints, non-skinning sealants have
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