Shin-Etsu Pure Sealant — Ultra-Low Siloxane Outgassing, One-Component Oxime-Type Room-Temperature-Curing Silicone Sealant for Cleanrooms

Shin-Etsu Pure Sealant is a one-component silicone sealing material that cures at room temperature by reacting with moisture in the air to become an elastic sealing material with outstanding adhesiveness. It is engineered for cleanrooms requiring an extremely high degree of cleanliness, and for airtight sealing of cleanroom joints and semiconductor production equipment where control of chemical contaminants is critical — making it one of the lowest-outgassing silicone sealants available for cleanroom applications.

• Excellent durability, heat resistance and weather resistance
• Low-molecular-weight dimethyl siloxane is almost not evaporated, ensuring ultra-high cleanliness
• Outstanding adhesiveness
• Easy-to-use one-component type; simply squeeze from the cartridge to apply
• Phosphorous, boron and antimony all below 1 ppm — minimal ionic-metal contamination
• 100% cohesive failure — high adhesion reliability

General Properties (not specified values)

Sheet properties measured per JIS K 6249 (cured 7 days at 23℃ / 50% RH); H-block per JIS A 5758 (float glass; 14 days at 23℃ / 50% RH, then 14 days at 30℃).

Cleanliness Verification

• Cyclic siloxane extraction (D3–D20): only D18–D20 detected, totaling ~120 ppm; D3–D17 below the 10 ppm detection limit — dramatically lower than the conventional product (ΣD11–20 = 9,890 ppm).
• Si-wafer outgassing adsorption test (JACA No.34): organic compounds adsorbed onto the wafer surface are far lower than conventional sealants, suitable for semiconductor wafer processing.

Colors & Packaging

• Colors: White, light gray, ivory, dark ivory, translucent
• Packaging: 330 ml cartridge (standard packaging: box of 20 cartridges)

Sealing of interior trim joints and around air filters (HEPA/FFU) in cleanrooms used for the manufacturing and processing of semiconductors and other precision electronic materials, as well as airtight sealing of semiconductor production equipment — anywhere low outgassing and low ionic-metal contamination are required.

Q1｜What is the key difference from conventional silicone sealants?

Its low-molecular-weight siloxane outgassing is extremely low (~60 ppm extracted; ~120 ppm cyclic siloxanes total) versus nearly 10,000 ppm for conventional products, preventing siloxane adsorption onto wafers and optics. It is purpose-built for cleanrooms and semiconductor equipment.

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

No. It is a one-component, room-temperature-curing (oxime-type) product that cures by absorbing atmospheric moisture (slowly releasing MEKO). Tack-free time is only ~3 min at 23℃ / 50% RH; cure speed varies with temperature and humidity.

Q3｜What materials does it bond to?

It offers outstanding adhesion to common cleanroom substrates (glass, metals, anodized surfaces, etc.), achieving 100% cohesive failure in H-block testing. Bonding surfaces must be cleaned of oil, dust and contaminants beforehand.

Q4｜What storage and handling precautions apply?

Store in a cool (5–25℃), dry place away from direct sunlight. Use promptly after opening; reseal unused cartridge and keep cool and dark. Avoid application in cold or humid conditions, which can cause poor curing/adhesion. Clear and white grades may slowly yellow in storage without affecting performance. The cured surface cannot be painted. Keep caulking-gun air pressure below 0.3 MPa.

Q5｜What safety measures are required during use?

Keep the area well-ventilated during work and for at least 24 hours after application. Uncured sealant irritates skin and mucous membranes; avoid eye contact — if it enters eyes, flush with water for 15+ minutes and seek medical advice. MEKO is released during curing, so ventilate adequately; read the SDS before use.

Q6｜How does it differ from Pure Sealant S-type?

Both are one-component, ultra-low-outgassing cleanroom sealants. Pure Sealant is oxime-type with a wider color range (incl. white, translucent) and higher hardness (Shore A 44); the S-type is acetonetype, further reduces organic outgassing adsorbed onto wafers and bonds to an even broader range of materials, but is offered only in light gray and ivory. Choose S-type for the lowest wafer contamination; choose the standard grade for more colors and higher hardness.