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not be painted
except when they can be coated
with elastomerics of comparable elongation.
Silicones:
Derivatives of silicon produced by combining
silicon, oxygen, and organic materials.
Silicones have extremely high thermal stability
and are used as abrasives, lubricants, paints,
coatings and synthetic rubbers.
Silicones are available in a wide range of
compositions that are extremely effective in
high-movement joints. They have excellent
recovery capabilities, usually up to 100%.
Silicones have very little shrinkage, 3%, and a
tack-free time of only 1 – 3 hours. High-tensile
strength silicones with lower movement are
typically used in glazing (wet seal) applications.
Most silicones come in one-component
packaging. They have excellent adhesion to
almost all building products
if such substrates
are properly prepared.
They come in a variety
of standard or custom colors, as they cannot be
painted over, except for siliconized elastomerics.
Silicones contaminate all surfaces they
encounter, making it virtually impossible to seal
over with any other types of sealants. Only
abrasive methods can remove silicone residue or
primers.
Do not use silicones below grade,
submerged
or for horizontal applications subject to
vehicular traffic.
The uncured silicone can stain
or change the color of the substrates.
Pre-formed silicone and polyurethane tapes:
These are relatively new technologies in
urethane and silicone.