Hercules 25666 High-Temperature Silicone Sealant – Red, 10.3 oz Cartridge

The Hercules 25666 High-Temperature Silicone Caulk is a 100% silicone-based, one-component sealant engineered for professional sealing and bonding applications exposed to elevated temperatures and variable environmental conditions. This high-performance material provides a durable, flexible, and weather-resistant seal for industrial, HVAC, mechanical, and construction assemblies requiring long-term resistance to heat, vibration, and chemical exposure.

Details

• Manufacturer: Hercules
• Model Number: 25666
• Product Type: High-Performance Silicone Sealant
• Form: Cartridge
• Container Size: 10.3 fl oz (305 mL)
• Net Weight: 0.84 lb
• Color: Red
• Base Composition:
  • Polysiloxanediol
  • Octamethylcyclotetrasiloxane
  • Methylsilanetriyl-Triacetate
• Physical Form: Paste
• Odor: Vinegar-like (acetic cure)
• Cure Type: Acetoxy, single-component, 24-hour full cure
• Service Temperature Range: -80°F to 600°F (-62°C to 316°C)
• Flash Point: 199°F (93°C)
• VOC Content: 20 g/L
• Viscosity Rating: 20.5 mm²/s
• Flammability Rating: 1 (per ASTM D4359)
• Joint Movement Capability: ±25%
• Elongation: Permanently flexible after cure
• Application Temperature: All-season workability
• Adhesion Substrates: Wood, glass, metal, porcelain, ceramic, painted surfaces, plastics, rubber
• Applicable Uses: Perimeter sealing, glazing, HVAC ducting, valves, tanks, gaskets, flues, appliance trim, sanitary seals, and mechanical assemblies

Technical Application

The Hercules 25666 silicone sealant is designed for high-temperature and industrial sealing applications where long-term elasticity and environmental stability are required. The acetoxy-cure chemistry ensures a strong, heat-resistant bond suitable for assemblies exposed to sustained thermal cycling or vibration. It performs effectively in sealing joints, flanges, ducts, and metal housings within HVAC systems, industrial machinery, roofing assemblies, and marine or automotive installations. The cured silicone provides resistance to weathering, ozone, moisture, and aging, maintaining adhesion and flexibility over a wide temperature range.

Specifications

• Temperature Range: -80°F to 600°F continuous service
• Curing Time: 24 hours at standard ambient conditions
• Movement Capability: ±25%
• Application Areas: HVAC, refrigeration, construction, mechanical joints, sanitary and perimeter seals
• Consistency: Non-sag paste
• Bond Type: High-adhesion, flexible elastomeric joint
• Packaging: 10.3 fl oz cartridge (standard caulking gun format)
• Compliance: Meets professional-grade sealant performance for industrial service applications

Summary

The Hercules 25666 Red High-Temperature Silicone Sealant provides a durable, acetic-cure elastomeric bond capable of continuous performance from -80°F to 600°F. Its formulation ensures chemical stability, adhesion to multiple substrates, and consistent flexibility under vibration and thermal stress. Suitable for professional sealing in HVAC, mechanical, industrial, and construction environments.