How can silicone rubber cable self-extinguish and not drip under flame conditions, improving fire safety?
Publish Time: 2025-10-02
In modern industry, construction, rail transit, and power systems, cables are not only the "blood vessels" of electrical energy and signal transmission but also a critical component of safe operation. In the event of a fire, traditional cables without flame retardancy not only contribute to the spread of the fire but can also cause secondary damage due to molten dripping, releasing toxic fumes and seriously threatening personnel safety and equipment integrity. Thanks to its unique material properties, silicone rubber cable exhibits exceptional self-extinguishing and non-drip properties under flame conditions, making it an ideal choice for high-security applications and significantly enhancing fire safety.1. Material Nature: The Inorganic Skeleton Structure of Silicone RubberThe fire resistance of silicone rubber cable stems from the chemical structure of its insulation and sheathing materials—silicone rubber. Unlike traditional carbon-chain polymers like polyvinyl chloride or polyethylene, silicone rubber is a polymer material with a silicon-oxygen backbone. Its molecular backbone consists of alternating silicon and oxygen atoms, with organic pendant groups. This gives it exceptional thermal and chemical stability. When exposed to high temperatures or flames, silicone rubber does not experience carbon chain breakage and melt-drip like organic polymers. Instead, it gradually decomposes and forms a dense, hard, inorganic silica ceramic-like protective layer.2. Self-Extinguishing Mechanism: From Combustion to Carbonization, Isolating Oxygen"Self-extinguishing" refers to the material's ability to quickly cease combustion once the fire source is removed. When exposed to flames, the surface of a silicone rubber cable is first heated, causing the organic side groups to oxidize and decompose, releasing a small amount of flammable gas. This process is brief and controllable. As the temperature rises, the Si-O backbone within the silicone rubber begins to rearrange and oxidize, ultimately forming a continuous silica ash layer on the cable surface. This ash layer has extremely low thermal conductivity, effectively isolating the external flame from the internal material while preventing further oxygen penetration, interrupting the combustion reaction due to oxygen depletion. Once the fire source is removed, the combustion process quickly ceases, achieving "self-extinguishing." This process does not require halogen flame retardants, is inherently flame-retardant, and is more environmentally friendly and safe.3. No-Drip Property: Key to Preventing Fire SpreadTraditional PVC cables soften and melt when burned, forming high-temperature droplets. These droplets not only carry flames and can ignite combustibles below, causing the fire to spread vertically, but the droplets themselves are also extremely hot, posing a direct threat to personnel and equipment. Silicone rubber, on the other hand, does not melt or flow at high temperatures; its decomposition process is carbonization rather than melting. The resulting protective silica layer maintains structural integrity, firmly encasing the internal conductor and insulation, and effectively preventing material dripping. Experiments have shown that even under open flames exceeding 800°C, silicone rubber cable retains its basic shape without producing droplets, significantly reducing the risk of fire spread.4. Low Smoke and Halogen-Free: Improving Fire Escape SafetyIn addition to being self-extinguishing and non-drip, silicone rubber cable produces virtually no black smoke or toxic gases when burned. Traditional halogen-containing cables release highly toxic and corrosive gases such as hydrogen chloride and dioxins when burned, which not only harm the human respiratory system but also corrode equipment. Silicone rubber is primarily composed of silicon, oxygen, carbon, and hydrogen. Its combustion products are primarily water vapor, carbon dioxide, and silicon dioxide. Its smoke density is extremely low and halogen-free. In the event of a fire, its low smoke properties help maintain clear vision, buying valuable time for evacuation and firefighting.The fundamental reason silicone rubber cable is "self-extinguishing" in flames is due to the inherent advantages of its inorganic-organic hybrid material. Rather than adding flame retardants to "fight" combustion, silicone rubber cable transforms its chemical structure to actively form a protective barrier, fundamentally suppressing the spread of fire. This inherent safety makes it irreplaceable in enhancing fire safety. As society's fire safety requirements continue to rise, silicone rubber cable, with its superior flame retardant properties, has become an indispensable "lifeline" in modern electrical systems.
