2.2
PRIMERS
Provide a nonstaining, quick-drying type and consistency recommended by the
sealant manufacturer for the particular application.
2.3
BOND BREAKERS
Provide the type and consistency recommended by the sealant manufacturer to
prevent adhesion of the sealant to backing or to bottom of the joint.
2.4
BACKSTOPS
Provide glass fiber roving or neoprene, butyl, polyurethane, or
polyethylene foams free from oil or other staining elements as recommended
by sealant manufacturer. Backing shall be 25 to 33 percent oversize for
closed cell and 40 to 50 percent oversize for open cell material, unless
otherwise indicated. Backstop material shall be compatible with sealant.
Do not use oakum [, [_____]] and other types of absorptive materials as
backstops.
2.4.1
Rubber
**************************************************************************
NOTE: Class A is adequate for most applications.
Select Class B for petroleum oil or fuel resistance.
Select Class D for temperatures of minus 75 to 175
degrees C (minus 103 to 347 degrees F) with no oil
exposure.
Specify Type 2 closed cell when moisture may migrate
to the backing.
**************************************************************************
[_____] Cellular rubber sponge backing shall be ASTM D 1056, [Type 1, open
cell,] [or] [Type 2, closed cell,] Class [A] [B] [D], Grade [_____],
[round] [_____] cross section.
2.4.2
PVC
**************************************************************************
NOTE: Do not use open cell vinyl foam in moist
areas or below grade.
**************************************************************************
[_____] Polyvinyl chloride (PVC) backing shall be ASTM D 1667, Grade [VO
12] [_____], open-cell foam, [round] [_____] cross section.
2.4.3
Synthetic Rubber
**************************************************************************
NOTE: Use Option I and Type I for most
applications. Select Option II only if flame
resistance is NOT required. Type II provides the
highest ozone resistance.
**************************************************************************
[_____] Synthetic rubber backing shall be ASTM C 509, Option [I] [II], Type
[I] [II] preformed [rods] [or] [tubes].
SECTION 07920
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