Standard silicone sealants are combustible at high temperatures. Flame-retardant formulations can self-extinguish when the ignition source is removed but do not provide true fireproof protection. Use certified fireproof sealants for applications with stringent fire-resistance requirements.
1. Overview of Silicone Sealants
Silicone sealants are elastic adhesives based on polysiloxane polymers. They are widely used in construction, automotive, and appliance industries due to their excellent weather resistance, UV stability, and strong adhesion. However, their organic components pose a combustion risk at elevated temperatures.
2. Mechanism of Combustion and Temperature Range
Conventional silicone sealants (e.g., those based on “107” grade) begin to decompose and burn between 200–300 °C. Combustion occurs as the organic siloxane backbone and terminal organic groups break down and oxidize, producing visible flame and combustion byproducts.
3. Flame-Retardant Silicone Sealants
To enhance safety, manufacturers add flame-retardant additives to silicone sealants. These formulations meet the fire-performance requirements of GB/T 24267-2009 (“General Technical Conditions for Sealants”) and will self-extinguish once the flame source is removed. However, under continuous flame exposure, the sealant layer still burns and chars, failing to maintain structural integrity in a real fire.
4. Difference between Flame-Retardant and Fireproof Sealants
-
Flame-Retardant Sealants: Contain flame-retardant additives for self-extinguishing behavior but will burn when exposed to sustained fire.
-
Fireproof (Firestop) Sealants: Incorporate inorganic intumescent materials that expand under heat to form an insulating char layer. These are designed for fire-resistance applications—such as wall or floor penetrations—to preserve compartmentation during a fire.
5. Relevant Fire-Resistance Standards
-
DIN 4102 B2: Classification for normally combustible materials; some industrial silicone sealants fall into this category even after curing.
-
GB/T 17646-2016: China’s classification of building material combustibility; ordinary silicones are typically rated B1 (difficult to burn) or B2 (combustible), so product test reports should be reviewed carefully.
6. Safe Selection and Application Guidelines
-
High-Rise Buildings and Fire Compartments: Avoid standard or flame-retardant silicones; use fire-stop sealants certified for the specific fire rating required.
-
Interior Finishes and Concealed Spaces: For cable and pipe penetrations, choose intumescent fire-stop materials to maintain fire separations.
-
Installation and Maintenance: Store sealants away from open flames and heat sources. Allow full curing before exposure, inspect periodically for aging or cracking, and replace any compromised sealant.
7. Conclusion
Silicone sealants contain organic components that burn at 200–300 °C. Flame-retardant grades can self-extinguish but will still burn under continuous flame. For applications demanding true fire resistance, certified fire-stop sealants with intumescent performance must be used to ensure building safety.
