DOWSIL™ SH 780 Sealant — Wide-Temperature, One-Part Neutral-Cure Oxime-Type Room-Temperature-Vulcanizing (RTV) Silicone Sealant (JIS A 5758 G-20LM / G-30SLM Specified)

DOWSIL™ SH 780 Sealant is a one-part, neutral-cure (oxime type) RTV sealant. It easily extrudes in any weather and cures quickly at room temperature; this cold-applied, non-sagging silicone material cures to silicone rubber upon exposure to atmospheric moisture. Combining outstanding adhesion, inherent waterproofness and wide-temperature flexibility, it meets JIS A 5758 G-20LM and G-30SLM (SR-1-9030G) and JSIA F☆☆☆☆, making it a high-performance choice for exterior wall joints, window/door caulking and general-purpose sealing and bonding.

• One-part sealant for ease of use
• Cures to a flexible silicone elastomer
• Nonacidic cure enables use on a variety of substrates without corrosion
• Non-sag — does not slump in vertical or overhead joints
• Excellent adhesion to various metals (except copper/brass), glass, tiles, earthenware, etc.
• Inherently waterproof
• Remains flexible over a wide temperature range (-40 to 150℃)
• Greater UV stability and temperature and weather resistance than organic sealants such as urethane and modified silicone sealants
• Meets JIS A 5758 G-20LM / G-30SLM (SR-1-9030G) and JSIA F☆☆☆☆

Typical Properties (not intended for preparing specifications)

JIS = Japan Industrial Standard.

JIS A 5758 (G-20LM / G-30SLM) Test Results (with DOWSIL™ Primer-D3(RF))

Colors & Packaging

• Colors: Clear, white, aluminum, gray, light-gray 2, umber, dark brown, black, and stain
• Packaging: 330 ml disposable plastic cartridge
• Usable life: 12 months from date of manufacture when stored in a cool and dark space

General-purpose sealing and bonding, space-filling rubber adhesive, and caulking and sealing of window and door frames — including exterior wall joints. Use DOWSIL™ Primer-D3(RF) for glass, metal and varnished metal, or DOWSIL™ Primer-B for wood, mortar and concrete, to improve adhesion and durability; adhesion should be tested on the actual substrate before application.

Q1｜What type of sealant is it, and how does it compare with urethane or modified silicone sealants?

It is a one-part, neutral-cure (oxime-type) RTV silicone sealant. Compared with organic sealants such as urethane and modified silicone, SH 780 offers greater UV, temperature and weather resistance, stays flexible across a wide -40 to 150℃ range and is inherently waterproof, giving longer durability.

Q2｜How does it cure? Is heat or two-part mixing required?

No. It is a one-part, room-temperature-curing product that cures to silicone rubber on exposure to atmospheric moisture. Tack-free time is only about 6 minutes (JIS); it is cold-applied and extrudes in any weather, with cure speed varying by temperature and humidity.

Q3｜What substrates does it bond to, and is a primer needed?

It adheres well to many metals (except copper/brass), glass, tile, earthenware, aluminum profiles, stainless steel, coated metal, various plastics and rubbers, mortar/concrete and wood, achieving 100% cohesive failure on most substrates. DOWSIL™ Primer-D3(RF) is recommended for glass, metal and varnished metal; DOWSIL™ Primer-B for wood, mortar and concrete. Verify adhesion on the actual substrate before application.

Q4｜What handling and storage precautions apply?

Surfaces must be clean and dry; protect the surface from rain for at least one day after application and prevent extensive joint movement during cure — a stain may appear around exterior wall joints. Keep air-gun pressure below 0.3 MPa. Contact with EPDM and chloroprene may affect sealant quality — test first. Store cool and dark; shelf life is 12 months un-opened, and high-temperature storage may cause discoloration.

Q5｜What safety measures and restrictions apply during use?

It evolves methyl ethyl ketoxime (MEKO) during curing, which can discolor/corrode brass and copper or crack acrylic resin and polycarbonate — do not use on these substrates. Alcohol and oxime sealants applied near or over each other may discolor. Do not use near open flame; not recommended above 150℃ continuous; not for aquariums. Solvent-based primers are highly flammable. Prolonged heavy inhalation of MEKO may harm health — provide sufficient ventilation and refer to the SDS.