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Red 10 oz cartridge of Hercules high-temp silicone sealant

Hercules

Hercules 25666 Silicone Sealant 10 oz Cartridge Red High Temp

SKU CH-X4Q1-3Z4FM

Red high-temperature silicone sealant in a 10 oz cartridge resists mildew, mould and water while staying flexible from -80 °F to 600 °F

  • Withstands extreme heat up to 600 °F
  • Remains flexible down to –80 °F for cold climates
  • Stretches 500 % elongation without cracking
  • Meets ASTM C920 Class 25 and federal specs
  • Mildew, mould and waterproof resistance for durability

Product Identity

Hercules 25666 is a red silicone sealant supplied in a 10 oz cartridge for HVAC, duct and electrical sealing tasks. It is formulated for installers and maintenance technicians who need a flexible, waterproof bond that resists mildew and mould.

Deciding Specification

The sealant meets ASTM C920 Type S Grade NS Class 25 Use A, G and O plus TT-S-001543A and TT-S-00230C, confirming its suitability for high-movement joints. Buyers who require a different classification or a non-silicone chemistry should select another product.

Sustained-Load Behaviour

After a 10-minute working window the material cures fully in one day and retains 500 percent elongation across a service range of -80 to 600 degrees F. It stays flexible and waterproof through repeated thermal cycling rather than hardening or cracking under constant stress.

Highlights

  • Withstands extreme heat up to 600 °F
  • Remains flexible down to –80 °F for cold climates
  • Stretches 500 % elongation without cracking
  • Meets ASTM C920 Class 25 and federal specs
  • Mildew, mould and waterproof resistance for durability

Specifications

BrandHERCULES

Questions about this item

What does the 600 °F maximum temperature mean for a real HVAC or exhaust repair?

The sealant remains stable and flexible up to 600 °F, so it will not degrade on hot ductwork, flues or engine components that reach that temperature.

Which standards does the ASTM C920 Type S Grade NS Class 25 rating actually cover in practice?

The rating confirms the sealant meets movement-capability Class 25 and is approved for uses A, G and O, covering joints in HVAC, duct and electrical enclosures.

What size caulking gun or nozzle fits the 10 oz cartridge?

The 10 oz cartridge uses a standard 1/10-gallon caulking gun and accepts typical screw-on nozzles for silicone sealants.

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