Moisture proof scheme for tunnel cables: magnesium hydroxide anti-corrosion modification process
In modern infrastructure construction, tunnel engineering, as a key component of transportation, energy transmission, and other critical areas, has received much attention for its safety and stability. As the core link of power and signal transmission, the operation status of the cable system directly affects the safety performance of the entire project. However, due to the humid and poorly ventilated environment of tunnels, as well as the possibility of groundwater infiltration, cables are prone to insulation aging, short circuits, and even fires caused by long-term exposure to high humidity environments.
How to enhance the moisture and corrosion resistance of tunnel cables has become an important issue in engineering design and construction. In recent years, magnesium hydroxide, as an environmentally friendly inorganic flame retardant, has gradually matured in the modification of cable materials and demonstrated good corrosion resistance and moisture resistance, providing new ideas and technological paths for solving the environmental challenges faced by tunnel cables.
1、 The main environmental challenges faced by tunnel cables
The internal environment of tunnels is complex and varied, especially in mountainous, underwater or urban underground engineering, where cables are often exposed to the following adverse conditions:
High humidity: The air circulation inside the tunnel is restricted, especially during the rainy season or near water sources, where the moisture content in the air is high, which can easily cause condensation on the surface of the cable.
Chemical corrosion: Some tunnels suffer from acidic gases (such as hydrogen sulfide) or salt spray erosion, which accelerates the aging and corrosion of the cable outer sheath.
Mechanical stress: During the cable laying process, it may be subjected to external forces such as compression and bending, which can affect its structural integrity.
Fire risk: In the event of a short circuit or overload, cables may become a medium for the spread of fire sources, causing serious consequences.
Faced with these challenges, traditional cable materials such as PVC and PE are no longer able to meet increasingly stringent protection requirements, and there is an urgent need to improve their comprehensive performance through material modification.
2、 The application advantages of magnesium hydroxide in cable materials
Magnesium hydroxide (Mg (OH) ₂) is a white powdery inorganic compound with excellent thermal stability and flame retardancy. In recent years, with the increasingly strict environmental regulations, magnesium hydroxide has been widely used in the wire and cable industry, especially in the manufacturing of high-performance environmentally friendly cables, due to its low toxicity, halogen-free, smoke suppression and other characteristics.
1. Improved corrosion resistance performance
Magnesium hydroxide has strong alkalinity, which can neutralize acidic substances and effectively inhibit the corrosive effect of acidic gases on the outer sheath of cables. In humid environments, it can also form a dense protective film, reducing the penetration of water molecules into the internal structure of the cable, thereby delaying the material aging process.
2. Excellent flame retardant and smoke suppression effect
When cables encounter high temperatures or flames, magnesium hydroxide begins to decompose at around 340 ℃, releasing a large amount of water vapor and absorbing heat, playing a role in cooling and flame retardancy. At the same time, its decomposition product is magnesium oxide, which does not produce toxic gases and greatly reduces the secondary hazards during fires.
3. Environmental protection and safety
Compared with traditional halogen containing flame retardants, magnesium hydroxide does not contain halogen elements and does not release harmful gases during combustion, which is in line with the current development direction of green building materials and suitable for engineering projects with high environmental protection requirements.
3、 Technical implementation of anti-corrosion modification process for magnesium hydroxide
The application of magnesium hydroxide in the modification of cable materials requires optimization from multiple aspects such as formula design, processing technology, and finished product testing to ensure its stable performance and feasibility for industrial production.
1. Material ratio optimization
Adding an appropriate amount of magnesium hydroxide (usually 60% -80%) to the cable sheath or insulation layer material, combined with other additives such as coupling agents, plasticizers, antioxidants, etc., can significantly improve the material's moisture and heat resistance and mechanical strength. At the same time, the formula ratio should be adjusted according to specific usage scenarios to avoid material brittleness or processing difficulties caused by excessive filling.
2. Surface treatment technology
In order to enhance the adhesion between magnesium hydroxide particles and organic substrates, coupling agents such as silane and titanate esters are often used for surface modification treatment. After treatment, magnesium hydroxide is more easily uniformly dispersed in the polymer system, thereby improving the overall performance of the material.
3. Processing technology control
Magnesium hydroxide belongs to inorganic fillers. During the processing, attention should be paid to controlling the mixing temperature and shear rate to prevent premature decomposition due to high temperature. In addition, it is recommended to use a twin-screw extruder for blending granulation to ensure uniform material mixing and improve the consistency of finished product quality.
With the continuous advancement of infrastructure construction in our country, the number of tunnel projects continues to increase, and the performance requirements for cable systems are also constantly improving. Magnesium hydroxide, as a green and environmentally friendly new material, has broad application prospects in cable modification.