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Guide to Using High-Temperature Silicone Sealants

Guide to Using High-Temperature Silicone Sealants

High-temperature silicone sealants can withstand temperatures as high as 600 degrees Fahrenheit and are resistant to aging, vibrations and shock. They are specially formulated to seal and encapsulate heating elements and industrial seals. High-temperature silicone is designed to withstand high temperatures when cured, typically up to 500°F, but some formulas are rated up to 572°F.

High temperature silicone sealants with an NSF certification are used in foodservice applications or where food contact may occur and high-temperature performance is needed. This type of high-temperature silicone is formulated to perform at up to 600 degrees Fahrenheit during intermittent exposure. A good high-temperature silicone will meet MIL-46106 Type 1 FDA and USDA requirements.


High Temperature Silicone Sealant - American Sealants 600
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Electrical Grade Self Leveling Silicone - American Sealants 306
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Multi Purpose Commercial Grade RTV Silicone
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worker using a silicone tube

Silicone

Silicone sealant is a liquid form of adhesive, though it looks, feels and acts like a gel. It is formed with a different type of chemical makeup compared to other, more organic polymer-based adhesives. Unlike those other adhesives, silicone is resistant to chemicals, moisture and weathering. It also keeps elasticity and stability in both high- and low-temperature conditions.

Silicone sealants require curing, which means they must dry. The temperature to cure the silicone can be anywhere between 50t and 100 degrees Fahrenheit, and there needs to be between 5 and 95 percent humidity for the silicone to properly cure. It can take as little as 24 hours to cure, but a thick application of sealant can take longer, sometimes up to 48 hours.

Silicone sealants can emit a strong and long-lasting odor and can take a considerable time to be fully cured., Their benefit is that they can be used in glass assemblies. Pure silicone is not paintable, but it will stay flexible at a wide range of temperatures, is waterproof, bonds well and won’t support mildew growth.

Industrial silicone is best used for sealing and bonding applications. Silicone has formulations that include electrical grade, low-odor, paintable and high-temperature. Silicone is used in a variety of industries including plumbing, refrigeration, HVAC, commercial and residential.

Types

High modulus, low modulus, neutral cure and acetoxy cure are the most commonly used silicone types. Low modulus will need just a low force to stretch it and will be more elastic, whereas a high modulus is more rigid. Choose the type of modulus based on how much movement you will need.

Acetoxy silicones release a vinegar-smelling acetic acid as they cure, but they cure quicker. This type of silicone sealant has poor adhesion and doesn’t stick well to plastics, glass or aluminium. Neutral alkoxy sealants release alcohol as they cure and adhere to a great number of different materials. They take longer to cure.

Acid-cure silicones work best on non-porous surfaces like glass and glazed tile, but they can corrode metal and etch some plastics, while neutral-cure silicones are a better choice if you are using metal or wood.

motor block

Uses for High-Temperature Silicones

High-temperature silicones are often used in automobiles because they are ideal for a hot engine. Some of this type of silicone’s uses are valve covers, axle housings, water and oil pump seals, timing chain covers, fuel pump covers and solenoid covers. High-temperature silicones are very popular in areas where the joint or connection is exposed to high heat. This includes engine gaskets with forced induction systems.

High-temperatures silicones are also popular in industrial applications, such as pump and compressor gaskets, appliance door gaskets, humidifier gaskets, ductwork, insulating wire and cable and furnace door gaskets, amongst others. Silicone sealant is used in a variety of craft projects because of its flexibility. It is capable of bonding glass, tile, metals and woods. 

Even though silicone isn’t a good substance for weight-bearing seals, it is still a powerful enough adhesive for many construction jobs. Silicone sealant is used in bathrooms and kitchens because it can provide a clean and neat seal to sinks, showers and bathtubs, which helps prevent mildew residue. It’s for this reason that silicone sealant is used on windows and doors: It makes them airtight, eliminates air infiltration and won’t be affected by the weather.

Directions for Use

Surfaces must be clean and dry before use. Tool the sealant immediately after application. If you are using a cartridge, cut the nozzles at 45-degree angles to obtain the desired bead size. Use a caulking gun to apply the sealant by pushing it ahead of the nozzle. Tool the sealant immediately after the sealant is applied, and aim to get the tooling done within a 5- to 10-minute window.

This sealant can be applied overhead or to sidewall joints and surfaces without sagging, slumping or running off. When bonding materials and sealants, apply a bead of adhesive to one surface and immediately combine the two parts together. Then apply pressure to ensure the surfaces are in full contact.

You can apply the sealant at temperatures as low as -85°F, so long as the surface is dry and frost free. The sealant should be dry to the touch within 30 minutes, and it will be fully cured within the first 24 hours.

Never mix the sealant with other chemicals, and always don protective eye-wear when applying it. Be careful not to allow the adhesive to touch your skin. Do not breathe fumes. Keep out of the reach of children. After use, store the sealant in a cool, dry place between 40°F and 90°F. All the application equipment should be cleaned with warm water after use.

Questions? We are here to help!

Do you have questions about high-temperature silicone sealants? We are happy to help! At Hotmelt.com our team of experts can recommend a product for your particular project or application. Send us a message to get started!

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