The failure of a circuit is one of the main causes of fire. According to statistics, more than 35 % Fire accidents worldwide are caused each year by cable problems. These failures often result from the use of non -fireproof cables, damaged cable conductors, bad cable connections and aging cable insulation. Fire resistance is therefore crucial in the choice of cable materials.
Currently, The most common -resistant -resistant isolated cables on the market are mainly mineral insulation cables (Mi cables, Magnesium oxide insulation) and fire -resistant cables wrapped in mica ribbon. The two cables have good resistance to high temperatures and fireproof properties, But they also have certain limits in practical applications.
Defects
Although mineral insulation cables (Mi cables) have excellent performance, They are difficult to pose due to the complex installation process, High requirements for professional skills of building workers and high costs of raw materials, which makes them difficult to promote and apply on a large scale. What's more, MI cables have poor flexion performance, which increases the complexity and cost of the installation.
On the other hand, Fire resistant cables wrapped in mica ribbon require several layers of winding during the production process. Due to the limits of the manufacturing process, Mica bands are subject to defects in the joints, and the mica is easily carbonized, becomes brittle or even peels off at high temperatures, affecting its overall fire resistance properties. At the same time, The fire resistance of the cables wrapped in mica ribbon depends largely on the tightness and uniformity of the packaging, which makes quality control more difficult.
With the continuous deepening of research on Fire -resistant isolated cables, A high performance elastomer material and high temperatures was created : Ceramic silicone. It represents an important material innovation in the field of fire -resistant cables and offers a new solution to improve cable fire resistance.
The birth of the silicone ceramic cable : A material revolution
Traditional rubber cables are based on the addition of halogen flame delayers, But hydrogen chloride (HCl) and dioxin released during combustion are extremely toxic. The appearance of silicone rubber changed this situation. But ceramic silicone has not only flexibility and elasticity of silicone, but more importantly, when exposed to high temperatures greater than 500 ° C and the erosion of the flames, It will undergo a ceramic transformation to form a hard substance similar to ceramics, effectively preventing the spread of fire. More importantly, The longer the exposure time and the flame temperature, The more the ceramic layer formed by the ceramical silicone becomes solid, with heat resistance going up to 1200-1500 ° C, thus better protecting the driver from damage.
Evolution of materials : Synergy between silicone rubber and ceramic loads
Silicone rubber matrix : The main channel is a Si-O link (liaison energy 452 kJ/mol, far from 346 KJ/Liaison mol C-C), which gives it high temperature resistance (-60~250℃) and resistance to aging.
Ceramic load : Add ceramic powder to nanometric scale (Like the Al₂o₃-Sio₂ system), which melts in high temperature porcelain to form a "second protective layer".
Definition and essential difference : passive protection against active porcelain fire
The ceramic silicone cable is a fire -resistant cable with silicone rubber as a matrix and a composite ceramic load, which is fried in a ceramic body in the flames. The essential difference with traditional cables is :
Passive fire protection → Active porcelainization : Traditional cables rely on the flashy outer envelope layer (Like the Mica ribbon), While ceramic silicone cables obtain structural strengthening thanks to the own reaction of the material.
Environmental protection has been improved : products containing halogens and high smoke toxicity to halogen -free and low toxicity products, Compliant with the EU ROHS Directive.
Ceramic silicone cable structure
Here is a current layer structure of ceramic silicone cables (can be adjusted in different scenarios) :
Driver
The driver is generally made up of tinned copper wire or Copper driver without oxygen, and the twisted structure is 1+6+12 (Electric line core) or 1+6 (Earth line core) To improve flexibility and conductivity. In certain conceptions, The driver is aluminum alloy, both light and corrosion resistant.
Insulating layer
Interior insulation : The driver is directly covered with reticulated polyethylene (XLPE) or mica ribbon to ensure basic electrical insulation and mechanical protection.
Ceramic silicone layer : as a central fireproof layer, A ceramic silicone rubber material (such as a coating of methylvinylic silicone rubber compound) is generally used. It is flexible at room temperature and fried at high temperature (600-1300℃) to form a ceramic shell to isolate the fire source and maintain the insulation. In certain conceptions, The surface of this layer is serrated to improve adhesion with adjacent layers.
Shielding layer
A layer of metal shielding (such as a copper ribbon or a braided layer) is placed outside the nucleus of the power line and the core of the earth line, which has both electromagnetic shielding functions and earth. Driver ceramic silicone rubber is used as an armor layer in certain structures and contains a reactive sticky agent to improve adhesion to the insulating layer.
Filling and insulation structure
Filling material : The space between the souls of the cable is filled with glass fibers without alkali, fireproof loads or refractory mud to improve structural stability and fire resistance.
Positioning framework : A positioning frame with arc grooves is placed between several groups of drivers, and the position is fixed by prismatic connection holes to avoid moving the nucleus.
Sheath layer
Interior sheath : The inner silicone grips extruded ceramic, Associated with ribbon without rolled halogen and the ceramic silicone rubber ribbon (left/right alternate winding, overlap > 15 %), Form a composite fire cutting barrier.
Outer sheath : One matherian to low smoke and halogen free (LSZH) or a high temperatures resistant thermoplastic sheath (Like reticulated polyolefin) is used, Taking into account wear resistance requirements, corrosion resistance and environmental protection.
Technology De Base : High temperature ceramization mechanism
Ceramic silicone can be used as cable insulation layer. It can form a hard protective layer in the event of a fire and effectively protect the driver. This is a key research and application orientation in the fire -resistant cable industry. The heart lies in the high -temperature ceramization mechanism.
Ablation on porcelain : From molecular structure to macroscopic properties
Under the action of the flame, Ceramisal silicone undergoes the following dynamic processes :
Ambient temperature condition : Silicone rubber has an elastomer structure, the load is uniformly dispersed, The volume resistivity is ≥10unch delivery · cm and the radius of curvature is ≤6d (For example, a cable of a diameter of 10 mm can be folded at 60 mm).
Combustion at 350 ~ 1000 ℃ :
Stage 1 (350~600℃) : Silicone rubber breaks down to produce SIO₂ and CO₂, And the load begins to melt.
Stage 2 (600-1000°C) : The melted load forms a continuous ceramic skeleton and CO₂ gas escapes to form a porous structure (porosity 3050%), which increases the thermal insulation performance of 3 times.
Perspective of materials science: The triumph of synergy
This ceramic process is based on the synergistic effect of molecular silicone rubber chains and ceramic loads :
Silicone rubber molecular chain : offers initial flexibility and insulation.
Ceramic load : The glass phase al₂o₃-sio₂ flows at high temperature to fill the pores and increase the density of the ceramic layer.
Gazous pore training : The CO₂ produced by decomposition forms a closed cell structure with a thermal conductivity as low as 0,12 W/(m·K) (asbestos), considerably improving thermal insulation performance.
Key performance indicators :
Fire resistance time : Maintain power supply during ≥ 180 minutes in a flame at 950 °C (The highest level of IEC standard 60331).
Projections resistance : Complies with BS standard 6387 CWZ (triple test de combustion + projection + vibration).
Smoke density : light transmission ≥ 80 % (The traditional PVC cable has only 20 %).
Experimental verification :
Test carried out by the School of Sciences and Engineering of Materials of Tsinghua University : Meb shows that the thickness of the ceramic layer after combustion is uniform (1 has 2 mm) and that there are no cracks.
Rapport TÜV Rheinland : After removal of 1200 ℃/3h, The cable can still withstand a 1000V hold voltage test.
Comparison of fire -resistant cables
To better understand the advantages of the ceramisable silicone cable, We compare it with existing fire -resistant cables, such as mineral insulation cable (MI) and the mica ribbon fire cable :
| Criteria | Mineral insulation cable (MI) | Mica ribbon fire cable | Ceramisable silicone cable |
|---|---|---|---|
| Benefits | 1) Excellent overload protection capacity ; 2) Excellent resistance to corrosion and explosions. | 1) Excellent high temperature and fire resistance ; 2) Does not give off toxic smoke in the event of a fire. | 1) High mechanical resistance and excellent thermal shock resistance ; 2) Halogen-free, low smoke, low toxicity, self -extinguishable and environmentally friendly ; 3) Easy to machine and install. |
| Fire performance | Excellent | Excellent | Excellent |
| Thermal insulation | Insufficient ; insulation can react chemically with air humidity. | Insufficient ; The fall of the Mica ribbon reduces the effectiveness of the insulation. | Excellent ; Form a rigid ceramic layer now intact insulation. |
| Installation resistance | High | High | Weak |
| Installation current problems | 1) Sometimes non -compliant isolation resistance ; 2) Short-circuits possible during operating tests ; 3) Loss of aesthetics after retouching. | 1) Defects with the junctions of Mica ribbons, Risks of detachment affecting fire resistance. | / |
| Cost of the life cycle | Pupil (Material costs, important installation and maintenance) | AVERAGE (moderate materials and installation costs, But maintenance to be expected) | Weak (reasonable material cost, installation facile, long -term reliability) |
Performances techniques
| Criteria | Ceramisable silicone cable | Mica ribbon cable | Mineral insulation cable (MI) |
|---|---|---|---|
| Fire resistance time (950 °C) | ≥180 minutes | ≤90 minutes (Carbonization and drop of mica) | ≥240 minutes (But possible deformation) |
| Smoke density (%) | ≤15 | ≥50 | 0 (But very high cost of the copper sheath) |
| Installation cost | Weak (great flexibility, easy pose) | AVERAGE (Need for reinforced winding) | Pupil (Need for special connectors) |
| Lifetime | 30 ans (Excellent aging resistance) | 15 has 20 ans (progressive deterioration of mica) | 50 ans (But high maintenance costs) |
Overall, Ceramisable silicone cable represents a reliable fire resistant solution, economic and sustainable for projects requiring high fire safety.
Thanks to its ease of installation, its excellent insulation performance in the event of fire and its low cost of life cycle, It is an innovative alternative to traditional cables.
Ceramic silicone characteristics
As a new type of fire -resistant cable material, The unique characteristics of ceramic silicone are the cornerstone of its excellent performance.
Formation of a self -supporting ceramic body in a flame
Conventional rubber materials containing inorganic loads degrade or burn when exposed to flames, degradation or combustion products volatilizing, leaving behind inorganic residues or low resistance ashes. These residues are generally not cohesive or self -supporting and can even break into particles or dust, Dafer of fireproof efficiency.
However, When a specially formulated ceramisable rubber is exposed to a flame, it can be ceramized at temperatures ranging from 350 has 800 ° C or even more, Depending on the type of rubber and the formulation used, Single in a self -supporting porous ceramic body. At temperatures between 650 and 1000 ° C, ceramic silicone can keep its structural integrity for a while (0,5 has 2 or more hours), Thus playing an effective "passive fire protection" function and saving precious time for fire safety. This ceramic process is the most fundamental difference between ceramic silicone and traditional rubber materials.
Good resistance and excellent thermal shock resistance
The fritted silicone body in ceradius has a high hardness and produces a sound similar to that of ceramics when it is struck, indicating that he has good mechanical resistance. Good resistance to flexion and compression. The bending resistance of ceramicized silicone samples is much greater than that of conventional silicone and increases considerably with the increase in temperature.
What's more, Ceramisable silicone has excellent thermal shock resistance. In a simulation of the fire extinction process, When water has been sprayed on the high temperature sample, The fried ceramical silicon body has not cracked, which indicates that it can maintain its structural integrity under rapid temperature changes. This resistance to thermal shocks is essential to the reliability of the cable in the event of a fire, Because the fire scenes are often accompanied by spray of extinction water.
Halogen-free, low smoke, low toxicity, auto-extinguible, environmentally friendly
Unlike traditional cable materials containing halogenated flame delayers, Ceramic silicone can obtain a self-exhaustible fireproof effect without adding halogenated additives. It responds to the UL94V flammability classification-0 and has an oxygen index up to 38. After a few minutes of contact with the fire source, Smoke emissions will stop almost completely and no large amount of smoke will be generated during the subsequent combustion process.
What's more, Ceramic silicone is an environmentally friendly material that mainly produces non -toxic substances such as carbon dioxide, water and silica when burned, considerably reducing the risk of poisoning in the event of a fire. This makes it an ideal choice for applications with high environmental requirements.
Good electrical performance
Optimized ceramisable silicone with an excellent electrical properties : before sintering, Its volume resistivity is generally not less than 10¹⁵ Ω · cm, guaranteeing good cable insulation performance in normal working conditions. Even if the resistivity decreases with the increase in the sintering temperature, Its volume resistivity can always be maintained above 10⁷ Ω · cm after combustion at 1000 ° C during 30 minutes, thus guaranteeing the capacity of the cable to continue to provide energy or to transmit signals during a fire. The volume resistivity of traditional silicone before and after sintering is not less than 10¹⁵ and 10⁷ω · cm respectively.
Easy to treat
The preparation and production process of ceramic silicone material is similar to that of traditional silicone and can be treated using standard rubber treatment equipment (extruders, vulcanizers, injection molding machines, etc.). This eliminates the need for cable manufacturers to perform upgrades or large -scale equipment changes, thus simplifying the production process of fire -resistant cables and reducing production costs.
Fire -resistant ceramic silicone cable application
The main application of ceramisable silicone is that Average and low voltage cables fire -resistant, which are used to ensure the secure circulation of the current in the event of a fire and ensure the continuous operation of critical equipment. The cable industry has shown great interest in the development and application of this new type of fire -resistant insulating material and estimates that it offers large application prospects.
Ceramisable silicone compounds can be produced on the same equipment as conventional silicones, without requiring additional machines. The material has excellent extrusion and molding properties and can be used to make cables using conventional extrusion and vulcanization equipment, which considerably reduces production costs and improves the efficiency of production.
What's more, Ceramisable silicone can always keep its original elasticity at room temperature and will not become brittle or do not take off like the mica ribbon when cooked, And it can withstand spray and vibration tests, ensuring that cable can maintain good performance in various difficult environments. Since many serious fires in civil buildings in recent years have been linked to cables, There is a high demand for cables in fire -resistant civilian buildings. We expect that the medium and low voltage ceramic silicone cables are experiencing significant development in the future and becoming an important element of the fire -resistant cable market.
Summary and Perspectives
Ceramic silicone cables become a new choice in the cable industry due to their excellent fire resistance, their environmental protection characteristics and their easy treatment. With the continuous advancement of technology and the continuous expansion of the areas of application, Ceramic silicone cables will surely play a more important role in future areas of energy transmission and safety, and will help build a safer and more reliable company.