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OSI HM270 Construction Silicone Sealant
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At a Glance
Quick Decision Guide
Color
White
Size
10 fl. oz.
Sealant Type
One-Part RTV Silicone
Joint Movement
±25%
Temperature Range
-76°F to 350°F
Primary Materials
Glass, Ceramic, Aluminum & Primed Steel
Weather Resistance
Water, Weather & UV Resistant
Paintable
No
Why Choose This Product
Key Benefits
Permanent Flexibility
Accommodates ±25% joint movement
Weatherproof Seal
Forms a watertight bond for exposed applications
Wide Temperature Range
Withstands temperatures from -76°F to 350°F
UV Resistance
Resists ultraviolet light and harsh environmental exposure
Strong Adhesion
Bonds to many non-porous materials typically without primer
Glazing Applications
Suitable for glazing, curtain walls, windows and related assemblies
Product Information
Product Details
Specifications
Brand
OSI®
Part Number
1493960
UPC
028756977896
Product Type
Construction Silicone Sealant
Color
White
Size
10 fl. oz. (295 mL)
Sealant Type
One-Part RTV Silicone
Modulus
Medium
Joint Movement
±25%
Temperature Resistance
-76°F to 350°F
Compatible Materials
Glass, Ceramics, Aluminum, Primed Steel & Some Plastics
Primary Applications
Glazing, Curtain Walls, Windows, Skylights & Metal Assemblies
Water Resistance
Watertight
Weather Resistance
Yes
UV Resistance
Yes
Paintable
No
Coverage at 1/4" Bead
Approx. 31 ft.
Coverage at 3/8" Bead
Approx. 14 ft.
About This Product
Silicone Sealant for Glazing and Non-Porous Materials
OSI® HM270 Construction Silicone Sealant is a medium-modulus, one-part RTV silicone designed for glazing and sealing non-porous building materials. It cures at room temperature when exposed to moisture and provides strong adhesion, typically without a primer, to glass, ceramics, aluminum, primed steel, and some plastics.
Permanent Watertight and Weatherproof Seal
HM270 forms a permanently flexible, watertight bond with ±25% joint movement capability. It withstands temperatures from -76°F to 350°F and resists ultraviolet exposure and harsh environmental conditions for exterior and interior sealing applications.
Glazing, Curtain Wall and Building Applications
The sealant is recommended for structural or conventional glazing and curtain wall sealing involving glass, plastic, or metal. Additional applications include skylights, solar panels, ventilators, aluminum siding, windows, HVAC units, ductwork, recreational vehicles, and other compatible glass, plastic, and metal assemblies.
Application and Material Limitations
HM270 is not recommended for concrete, marble, brass, copper, oily woods, limestone, brick, lead, polyethylene, polypropylene, PTFE, green or vulcanized rubber, continuous water immersion, potable water systems, traffic-bearing joints, confined air-free spaces, or direct contact with reflective mirror coatings. The silicone is not paintable.
Common Questions
Frequently Asked Questions
What materials does OSI HM270 bond to?
HM270 provides adhesion to non-porous building materials including glass, ceramics, aluminum, primed steel, and some plastics, typically without requiring a primer.
Can OSI HM270 be used for exterior applications?
Yes. HM270 forms a watertight and weatherproof seal and is highly resistant to UV exposure and harsh environmental conditions.
How much joint movement can HM270 accommodate?
HM270 remains permanently flexible and accommodates ±25% joint movement.
What temperature range can OSI HM270 withstand?
The cured sealant withstands temperatures ranging from -76°F to 350°F.
How much coverage does a 10 fl. oz. cartridge provide?
A 10 fl. oz. cartridge provides approximately 31 ft. with a 1/4" bead or 14 ft. with a 3/8" bead.
Can OSI HM270 be painted?
No. Paint will not adhere properly to the silicone, so HM270 should not be used where a paintable sealant is required.
Can HM270 be used on concrete or masonry?
No. HM270 is intended primarily for compatible non-porous materials and is not recommended for concrete, marble, limestone, brick, or several other porous and incompatible surfaces.
Can OSI HM270 be used in continuously submerged applications?
No. HM270 is not recommended for joints subject to continuous water immersion, such as swimming pools and boats.