Silicone sealants for extreme temperatures

High-temperature sealant—the heat stopper

In some conditions, regular silicone sealant just won’t hold up. Heat-resistant silicone could be your perfect solution. Read our short guide to get the details on high-temp silicone sealant, including application tips.

High-temp sealant explained

High-temperature sealant are used for sealing, insulating, and bonding areas subject to extreme temperatures. Some high-temp silicone sealants can withstand temperatures as low as -60°C and as high as 343°C, while remaining flexible and resilient.

Along with heat resistance, silicone is valued for its strong adhesive and anti-mould properties, as well as its resistance to solvents, chemicals, water and moisture.

High-temperature silicone: Typical uses

High-temperature silicones are used in many industrial applications including plumbing, HVAC, refrigeration, and in the automotive industry.

Hot automotive engines present a problem for many common sealants since constant vibration is an issue, along with high temperatures. Heat-resistant silicone has proven its ability to seal valve covers, water and oil pump seals, axle housings, fuel pump covers, and more.

Industrial applications include pump and compressor gaskets, ductwork, and furnace door gaskets.

What about curing time? High-temp silicone sealant may be dry to the touch in as little as 30 minutes, but silicone must cure for 24 to 48 hours before it reaches its full strength as an adhesive.

Choosing a quality high-temp silicone sealant

In choosing a heat-resistant silicone product, keep the following considerations in mind:

  • What are the highest and lowest temperatures the area to be sealed will be subjected to?
  • Will the high-temp silicone be used as an adhesive (holding parts together), as a sealant or heat shield, or both?
  • Will the sealant be exposed to corrosive or caustic chemicals?
  • Is a fast curing time an issue?

After making a list of the exact properties needed for your application, start researching various high-temperature silicone sealants and choose the one that is the best fit.

Once you’ve chosen your product, follow the checklist below for successful application:

  1. Make sure surfaces to be sealed are clean and dry.
  2. Cut the nozzle of the sealant tube at a 45-degree angle.
  3. Using your caulk gun, apply a bead of sealant along the seam to be filled.
  4. Smooth the bead of sealant with a sealing tool, damp cloth, or gloved finger.
  5. Make sure you complete the smoothing within a few minutes. As the silicone begins to set, it will no longer be workable.

When preparing to re-seal an area, first remove the old sealant. Old silicone sealant is quite rubbery and may pull off in long pieces. Remove the rest with a putty knife or similar, taking care not to scratch the surface. Finally, wipe the area down with mineral spirits to remove any remaining residue before applying the new sealant.

Alternative to heat-resistant silicone replacement

When heat-resistant silicone is not called for, you may not need to replace your old sealant at all. Loctite Re-New is the one step, simple way to make joints look like new.

There’s no need to remove the old sealant - just clean it and apply Re-New directly on top. It’s easy to get smooth, professional results with the integrated smoothing tool applicator. It takes just a few minutes to apply and the sealant can be exposed to water again in 6 hours.