Introduction to the Application of Silica sol for Special Fire-Resistant Glass
#Application
·2025-08-21 16:43:06
Special fire-resistant glass is a key material for ensuring fire safety in fields such as construction and transportation. Its core function is to maintain integrity (prevent the penetration of flames and smoke) and heat insulation (prevent the transmission of high temperatures) during a fire. Silica sol, as a high-performance inorganic material, plays a significant role in the preparation of special fire-resistant glass due to its unique physical and chemical properties. The following is a detailed introduction to the basic properties, application scenarios, mechanism of action and advantages of silica sol.
Silica sol is a dispersion of nano-scale silica (SiO₂) particles in water, with particle diameters typically ranging from 5 to 100 nanometers. It appears as a colorless, transparent or pale yellow liquid. Its core features include:
- High dispersibility: The nanoparticles are uniformly dispersed, with a large specific surface area (usually > 100m²/g), and can fully contact with other materials.
- Good adhesion: The particle surface is rich in hydroxyl groups (-OH), which can form strong chemical bonds with materials such as glass and inorganic fibers, and has a high bonding strength.
- High-temperature resistance: The melting point of silica is as high as 1723℃. Silica sol does not decompose at high temperatures but instead dehydrates and solidifies to form a dense SiO₂ glass body.
- Inorganic environmental friendliness: The composition is only SiO₂ and water, without any volatile organic compounds (VOCs). It does not produce toxic gases at high temperatures and meets the environmental protection requirements for fire safety.
The characteristics of silica sol are highly compatible with the functional requirements of special fire-resistant glass, and its application is mainly concentrated in the following types of products:
Laminated fire-resistant glass is composed of two or more pieces of glass with a fire-resistant adhesive layer sandwiched between them. Silica sol mainly serves as the core component of the inorganic fire-resistant adhesive layer.
- Non-insulating type: Through the strong adhesion between silica sol and glass, it ensures that the glass does not break or fall off during a fire, maintaining its integrity (such as for fireproof partitions and fireproof Windows).
- Thermal insulation type: Flame-retardant fillers such as aluminum hydroxide and expanded vermiculite can be added to the silica sol. At high temperatures, an expanded thermal insulation layer is formed. Meanwhile, the silica sol itself solidifies into a SiO₂ barrier, double blocking heat transfer (such as for walls and curtain walls close to fire sources).
By applying a silica sol-based coating on the surface of ordinary glass, its fire resistance can be enhanced:
- After the coating dries, a nano-SiO ₂ film is formed, enhancing the hardness and high-temperature resistance of the glass surface.
- During a fire, the silica sol in the coating solidifies upon heating, forming a dense protective layer that delays the glass from cracking (suitable for scenarios that require lightweight and low-cost renovations).
Silica sol is used as a binder between glass and inorganic fiber layers such as asbestos and glass fiber.
- By taking advantage of its high adhesive property, the fiber layer is firmly combined with the glass. The fiber layer provides support at high temperatures, while the silica sol fills the gaps to form an overall fireproof structure, enhancing the impact resistance and integrity of the glass (such as in high-frequency vibration scenarios like subways and tunnels).
The core role of silica sol in special fire-resistant glass is to meet the requirements of "integrity" and "heat insulation" through the physical-chemical synergistic effect:
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High-temperature curing and structural support (ensuring integrity)
At room temperature, the SiO₂ particles in silica sol form an initial bond through hydroxyl interaction. During a fire, the increase in temperature promotes rapid evaporation of water, causing SiO₂ particles to further aggregate and sint, forming a continuous dense SiO₂ glass body (similar to a ceramic structure). This structure is of high strength and high-temperature resistance. It can firmly fix glass fragments, preventing them from softening due to high temperatures or falling off due to impact, thereby blocking the penetration of flames and smoke.
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Thermal insulation barriers and heat reflection (Enhancing thermal insulation)
The thermal conductivity of the cured SiO₂ glass body is extremely low (about 0.1-0.2 W/(m · K)), which can effectively block heat transfer. If combined with expansive fillers (such as vermiculite), at high temperatures, the fillers expand to form a porous insulating layer, which works in synergy with the SiO₂ glass body to create a "double insulating barrier", keeping the temperature on the other side of the glass within a safe range (typically not exceeding 180℃ within 30 minutes of a fire).
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Inhibit the thermal cracking of glass
The thermal expansion coefficient of the silica sol coating or adhesive layer is close to that of glass, which can reduce the glass cracking caused by the difference in thermal stress at high temperatures. Meanwhile, nano SiO₂ particles can fill the micro-cracks on the glass surface and enhance its thermal shock resistance.
