TM 5-805-6
enough resilience to withstand limited displace-
swimming pools. These sealants have a low solids
content (about 20 percent) and cure by evaporation
ment vibration.
of solvent; consequently, they shrink too much for
(2) Preformed sealants. Gaskets, tapes, and
preformed foams are effective in sealing wall
many types of joints. After application, some of
these sealants may become tack-free in 24 hours
penetrations such as telephone, television, and
electrical outlets.
and then take 1 to 3 months to cure. During the
(3) Asphalt or oil- and resin-based sealants.
cure time, movement of the joint can damage the
These sealants perform well at first, but they
seal.
shrink, harden, crack, and lost adhesion which
(1) CSPE. An example of CSPE is hypalon.
CSPE is more often found in roofing as a mem-
may cause air gaps that will transmit sound.
brane than as a sealant in building joints. Cured
(4) Latex and acrylic sealants. In joints which
have little or no movement, latex and acrylic
CSPE sealants can withstand a joint movement of
sealants are effective in stopping sound transmis-
25 percent. They have good resistance to most
sion.
acids, alkalis, and petroleum products. CSPE seal-
(5) Elastomeric sealants. The elastomeric seal-
ants are available in colors and will accept oil-
ants discussed in this manual are good acoustic
based paints, but they are better left uncoated.
sealants, especially for joints that move.
(2) Polychloroprene. Polychloroprene (Neo-
(6) Other types of sealants. High costs limit
prene) sealants can withstand joint movement up
acoustic applications of otherwise suitable sealants
to 25 percent and provide excellent resistance to
based on butyl rubber or polymers of polychloro-
many chemicals, most petroleum products, and
prene or chlorosulfonated polyethylene.
water. Polychloroprene sealants are used to seal
m. Butyl sealants. Solvent-based butyl sealants
joints in swimming pools and joints between con-
are used where good water resistance is needed,
crete and asphalt.
their dark color is acceptable, solvent release is
not a problem, and the joints move less than 10
9. Curing. Caulking may be slow curing; some
percent of the joint width. A few specially formu-
caulkins and acoustic sealants never fully cure.
lated butyl sealants will tolerate joint movement
Most sealants must cure to be strong enough to
as high as 20 percent.
absorb the joint's motion and to resist stresses
(1) Butyl sealants consist essentially of butyl
imposed by outside forces. The sealant cure must
rubber and other materials dispersed, and at least
be slow enough to permit the material to be
partially dissolved, in an organic solvent.
applied and fast enough to complete the cure
(2) Applications include joints between doors
before the sealant is stressed by temperature
or windows and masonry and between cap flash-
changes or by its intended usage.
ings and parapet walls. Butyl sealants cure by
a. Single-component sealants. Single-component
evaporation of the solvent with little shrinkage.
sealants cure by absorbing moisture from the air
The presence of solvent precludes most butyl seal-
or by evaporating solvent or water from the
ants from applications where volatile organic com-
sealant into the air. Silicone and polyurethane
pounds are severely restricted. Butyl sealants are
single-component sealants cure by acquiring mois-
very flexible, have excellent resistance to water
ture from the air, so shrinkage is minimal or none.
and weather, and bond well to masonry and
Sealants dispersed in water or solvent cure by the
metals; consequently, butyl sealants are often used
loss of the water or solvent which causes some
in joints between dissimilar materials.
shrinking during the cure. Single-component sys-
(3) Some butyl sealants are available in col-
tems are slow to cure and may require several
months to develop their full strength. High tem-
ors. Butyl sealants are vulnerable to attack by
perature and humidity will hasten the slow cure.
petroleum products and oxidizing chemicals, in-
A thick bead cures slowly and may remain perma-
cluding ozone. Butyl sealants can be painted and
are available in cartridges for caulking guns, in
nently soft near the middle.
containers for putty knife application, and in
b. Multi-component sealants. Rather than de-
preformed beads, tapes, and extrusions.
pend on moisture for curing, these sealants cure
n. Chlorosulfonated polyethylene (CSPE) and
by the reaction of two or more components, each of
which has a long shelf life. When the components
polychloroprene sealants. These materials are
are mixed together the resulting sealant cures in a
available as sealants and as fluid-applied mem-
branes, both of which provide good resistance to
short time. The components may be two or more
polymers, a curing agent, or a catalyst to promote
water and many chemicals, including most petro-
polymerization. Increased temperature and humid-
leum products. CSPE is often used in roofing,
ity will shorten the cure time. Additionally, the
while polychloroprene is used underwater, e.g., in
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