Dowsil silicone sealants

Description

[Dow] Dow produces numerous types of one-part, neutral-cure Silicone materials that can be used as adhesives/sealants. These room temperature vulcanizing (RTV) silicones were introduced in the 1960s and cure upon exposure to atmospheric moisture. There are two type of neutral cure RTV silicones. The first type is an alkoxy neutral-cure that releases methanol upon cure. The alkoxy neutral cure silicones are considered suitable for use on all types of metal without risk of corrosion. The second type is an oxime neutral-cure silicones that releases methyl ethyl ketoxime. These withstand temperature better than alkoxy-cure but can cause stress-cracking in some plastic boards, such as polycarbonate and acrylics.

General properties for Dowsil silicones include:

• Stability over a wide temperature range – When fully cured, most can be used at temperatures ranging from -85° to 599°F (-65° to 315°C).
• Weather resistance – High resistance to UV rays, radiation and weather prevents our products from hardening, cracking, crumbling, drying and becoming brittle.
• Chemical stability – Do not readily degrade, even under long-term exposure to many chemicals and atmospheric pollutants.
• Good bond strength – Provide good adhesion to a wide variety of industrial materials, including glass, ceramics and wood masonry; painted surfaces; and many metals and plastics.
• Low flammability – In fire conditions, silicone adhesives/sealants are reluctant to burn. Many products comply with UL flammability standards.

Commercial name	Cure type	Applications	Working Properties	Benefits/Risks	Material Analysis	Product website
Dowsil 580 Neutral cure	Oxime neutral cure; one component	General Glazing; Weather-sealing applications for windows, doors, glass, metal, masonry		Not recommended for water immersion; do not use on structural glazing; may discolor copper and brass; cannot be painted; not for use on polycarbonates	Testing results	Dowsil 580
Dowsil 737 Neutral Cure	Oxime neutral cure; one component	Adhesion to most materials; Adhering plastic moldings to plastic substrates for trim applications; Waterproofing electrical components		Not recommended for water immersion, or use on painted surface; may discolor brass, or copper; may stress craze polycarbonates	MMA 2016; BKM 2017; BKM 2018; BKM 2018; Testing results	Dowsil 737
Dowsil 739 RTV	Alkoxy cure with moisture; one component	Adheres well to unprimed metals, ceramics and glass and some plastics;		Does not adhere to Teflon, polyethylene, polypropylene, or highly plasticized plastics or rubbers.	MMA 2016; Testing results	Dowsil 739
Dowsil 791 Weatherproof Sealant	Alkoxy cure with moisture; one component; medium modulus	Good for inside display envelope: glass and metal joins; glass and glass joins; Goppion uses black, grey, white due to aesthetic reasons (transparent caulks yellow within 5 years)			MMA 2016; AMNH 2019; MMA 2021; white is unsuitable; Testing results	Dowsil 791
Dowsil 795 Building Sealant	Alkoxy cure with moisture; one component; medium modulus	Structural and nonstructural glazing; weather sealing of most common construction materials including glass, aluminum, steel, painted metal, EIFS, granite and other stone, concrete, brick and plastics	Extra thick; skins over too quickly	Not recommended for water immersion, or wet or cold surfaces; not paintable	MMA 2016; MMA 2020; MMA 2021; Testing results	Dowsil 795
Dowsil 9-1374 Silicone sealant	Alkoxy cure with moisture; one component	Used for formed in place gaskets; provides strong flexible bond for movable or expanding joints, such as when bonding materials with different thermal expansion rates such as glass to metal, or glass to plastic or metal to plastic			MMA 2016; Testing results	Dowsil 9-1734
Dowsil 3145 RTV Mil-A-46146 Adhesive / Sealant	Alkoxy cure with moisture; one component	Sealing openings in modules and housings; Adding mechanical stability to individual components; adheres to glass and nylon	Skin-over time = 15 min; hard to work with; requires experienced person to apply and clean up; viscous, does not flow	Good adhesion cannot be expected on non-reactive metal substrates or non-reactive plastic surfaces such as Teflon, polyethylene or polypropylene.	BKM 2016; BKM 2017; AWNH 2019; Testing results	Dowsil 3145
Dowsil 7091 Adhesive Sealant	Alkoxy cure with moisture; one component	Provides strong but flexible bond, such as when bonding materials with differing thermal expansion rates, e.g. glass to metal or glass to plastic	Skin-over time = 15 min; This one has been used in museums	For maximum adhesion, the use of DOWSIL™ 1200 OS Primer is recommended.	BKM 2016; BKM 2017; MMA 2017; AMNH 2019; Testing results	Dowsil 7091
Dowsil 993	Two-component, fast cure alkoxy neutral-cure	Good for glass to glass and glass to metal	Working time 10-30 minutes; This one has been used in museums	No primer is needed; Resistant to UV and ozone		Dowsil 993 Structural Glazing Base and Catalyst
Silastic 1080 RTV	Alkoxy cure with moisture; one component	Provides reliable, long-lasting bonds with a wide range of substrates, including ceramics, metals, glass and filled plastics,		Long service life, wide operating temperatures, resistance to oils and solvents; water and steam resistant	Testing results	Silastic RTV

Personal Risks

• Wear eye, hands, and respiratory protection.
• SDS: sheets

Collection Risks

Literature indicates the sealant has no significant volatile components. Some silicones have curing byproducts of ethanol, peroxides or ketones. Risk to museum collections could occur if an object comes in contact with the sealant causing possible staining or adhesion (if not fully cured).

Resources and Citations

• AIC Conservation Wiki: Caulk Sealants to Seal Exhibit Cases
• Antala: Dow Silicone Selection guide (contains information on 3145 and 7190)
• Americas: Dow Silicon Technical Manual (contains information on 791, 795 and 993)