Product Information

Silicone
Sealants Dow Corning® 991 Silicone
High Performance Sealant

FEATURES Medium-modulus elastomeric sealant designed for weather-

• Improved aesthetic performance – proofing sensitive porous stone and metal panel substrates
reduces long-term residue rundown
on metal panels and reflective glass APPLICATIONS
or staining on porous substrates Dow Corning® 991 Silicone High Performance Sealant is particularly effective for
• Good working time and tooling sealing expansion and control joints, metal panel joints, curtainwall joints, joints
time between natural stone and perimeter seals around window frames. It forms a dur-
• All-temperature gunnability – able, flexible, watertight bond with most building materials. Dow Corning 991
from -29 to 50°C (-20 to 122°F), Silicone High Performance Sealant is intended to be applied in new and remedial
permitting application in all seasons construction.
• Medium modulus, high movement
capability – can accommodate ±50 TYPICAL PROPERTIES
percent movement in a properly Specification Writers: Please contact your local Dow Corning sales office or your Global
designed joint Dow Corning Connection before writing specifications on this product.
• Unprimed adhesion to most glass,
granite, GFRC, and fluoropolymer Method Test Unit Result
painted substrates As Supplied
Color Adobe tan, white, limestone,
• Excellent weatherability –
gray, bronze, black, custom colors
non-reverting silicone durability ASTM C 679 Tack-Free Time, 50% RH minutes 60
• Compatible with open-cell Curing Time, 50% RH at 25°C (77°F) days 7-14
polyurethane, closed-cell ASTM C 639 Flow, Sag or Slump inches (mm) 0.1 (2.54)
polyethylene and nongassing Working Time minutes 30-45
polyolefin backer rods
As Cured
• Available 20-year Limited
ASTM D 2240 Durometer Hardness, Shore A points 25
Weatherseal and Non-Staining
warranties As Cured – After 14 days at 25°C (77°F)
ASTM D 412 Ultimate Tensile Strength psi (MPa) 200 (1.38)
COMPOSITION ASTM D 412 Ultimate Elongation percent 750
ASTM C 794 Peel Strength, unprimed to
• One-part, pre-pigmented material glass, and fluoropolymer
painted substrates ppi (kN/m) >20 (3.50)

ASTM C 1248 Staining/Migration, white marble None

As Cured – After 21 days at 25°C (77°F)

ASTM C 719 Joint Movement Capability,
glass, aluminum percent ±50

DESCRIPTION High Performance Sealant cures to a

Dow Corning 991 Silicone High flexible elastomer on exposure to
Performance Sealant is a medium- atmospheric moisture, producing a
modulus elastomeric sealant specif- durable, weather-resistant seal with the
ically designed for weatherproofing ability to form strong bonds with most
sensitive porous stone and metal panel building materials. Because of its
substrates. It is a one-part silicone medium modulus and good adhesion,
formulation that requires no mixing it provides excellent weatherproofing
prior to use to obtain all its aesthetic performance in dynamically moving
properties. Dow Corning 991 Silicone building joints.
Dow Corning 991 Silicone High 2:1 where possible. Joint depth over PACKAGING
Performance Sealant meets the backer rod should be 1/8 to 1/2" (3 to Prepigmented Dow Corning 991 Sili-
following standards: 13 mm) and joint width from 1/4 to cone High Performance Sealant is
• ASTM Specification C 920, Type 1" (6 to 25 mm). Dow Corning available in 20-oz (591-ml) sausages
S, Grade NS, Class 50, Use NT, G, Technical Service should be consulted and 2-gallon (7.6-liter) pails.
A, M and O for joint applications outside published
• ASTM Specification C 719 ±50% guidelines. In all cases, movement of LIMITATIONS
movement the joint should not exceed ±50
This product is not intended for use:
percent of the original joint dimension.
• In structural glazing applications or
HOW TO USE where the sealant is intended as an
Preparatory Work Maintenance adhesive
The application surface must be clean, If sealant becomes damaged, cut out • In interior or shaded areas,
dry, sound and frost-free. Mask and replace the damaged portion with Dow Corning 991 Silicone High
adjacent surfaces and apply primer as Dow Corning 991 Silicone High Performance Sealant may yellow if
required, before installing an approved Performance Sealant not exposed to UV or sunlight;
back-up material. discoloration is most noticeable in
HANDLING PRECAUTIONS light colors
Application PRODUCT SAFETY INFORMATION • In areas where abrasion and
Apply Dow Corning 991 Silicone High REQUIRED FOR SAFE USE IS NOT physical abuse are encountered
Performance Sealant and tool so all INCLUDED IN THIS DOCUMENT. • In spaces totally confined from
joint sides are wetted out. (Wet tooling BEFORE HANDLING, READ atmospheric moisture during cure
of the sealant with liquid tooling aids PRODUCT AND MATERIAL • On frost-laden or damp surfaces
is not recommended.) In cases where SAFETY DATA SHEETS AND • For prolonged submersion in water
excess uncured sealant is inadvertently CONTAINER LABELS FOR SAFE • On surfaces that might bleed oils,
applied to adjacent surfaces, the USE, PHYSICAL AND HEALTH plasticizers or solvents – materials
sealant should be cleaned from sur- HAZARD INFORMATION. THE such as impregnated wood, oil-
faces before curing, using mineral MATERIAL SAFETY DATA SHEET based caulks, green or partially
spirits (follow solvent manufacturer’s IS AVAILABLE FROM YOUR vulcanized rubber gaskets, tapes,
safe handling recommendations and DOW CORNING REPRESEN- bitumen-impregnated boards, felts
local, state and federal regulations TATIVE, OR DISTRIBUTOR, OR or sheets
regarding solvent usage). BY CALLING YOUR GLOBAL • In below-grade applications
DOW CORNING CONNECTION. • On substrates made of polypropyl-
Remove masking immediately after ene, polyethylene, polycarbonate
sealant application. Under low tem- USABLE LIFE AND and polytetrafluoroethylene
perature and low humidity conditions, STORAGE (Teflon®1)
cure may be considerably longer. When stored below 27°C (80°F), • Where movement capability greater
Dow Corning 991 Silicone High than ±50 percent is required
Joint Design Performance Sealant has a shelf life of
12 months from date of manufacture. Dow Corning 991 Silicone High
A thin sealant bead will accommodate
Refer to product packaging for “Use Performance Sealant will not improve
more movement than a thick bead.
By” date. pre-existing staining or residue
Recommended width-to-depth ratio is

1
Teflon is a registered trademark of E.I. du Pont de
Nemours & Co.
rundown conditions. Surface appear- ensure that Dow Corning’s products
ance of any sealant will depend upon are safe, effective, and fully satis-
environmental conditions. factory for the intended end use.
Suggestions of use shall not be taken
This product is neither tested nor as inducements to infringe any patent.
represented as suitable for medical
or pharmaceutical uses. Dow Corning’s sole warranty is that
the product will meet the Dow Corning
HEALTH AND sales specifications in effect at the
ENVIRONMENTAL time of shipment.
INFORMATION
Your exclusive remedy for breach of
To support customers in their product
such warranty is limited to refund of
safety needs, Dow Corning has an
purchase price or replacement of any
extensive Product Stewardship organ-
product shown to be other than as
ization and a team of Product Safety
warranted.
and Regulatory Compliance (PS&RC)
specialists available in each area.
DOW CORNING SPECIFICALLY
DISCLAIMS ANY OTHER
For further information, please see
EXPRESS OR IMPLIED WAR-
our website, www.dowcorning.com,
RANTY OF FITNESS FOR A
or consult your local Dow Corning
PARTICULAR PURPOSE OR
representative.
MERCHANTABILITY.

LIMITED WARRANTY DOW CORNING DISCLAIMS

INFORMATION – PLEASE LIABILITY FOR ANY INCIDEN-
READ CAREFULLY TAL OR CONSEQUENTIAL
The information contained herein is DAMAGES.
offered in good faith and is believed to
be accurate. However, because 20-year limited Weatherseal and Non-
con-ditions and methods of use of our Staining warranties are available.
products are beyond our control, this Some testing may be required. Consult
information should not be used in your Dow Corning Technical Service
substitution for customer’s tests to representative for details.
Printed in USA Dow Corning is a registered trademark of Dow Corning Corporation.
Form No. 62-1145-01 AGP6146 ©2002 Dow Corning Corporation. All rights reserved.