We know that some wires and cables are flame-retardant. As the name suggests, their flame-retardant properties prevent combustion. Flame-retardant cables offer a unique advantage: they can achieve excellent flame-retardant properties through various methods. However, while these flame-retardant properties offer excellent flame-retardant properties, they can also have some undesirable side effects.
The flame-retardant properties of flame-retardant power cables are as follows:
Flame-retardant cables can be achieved through both physical and chemical methods, with chemical methods being the most widely used.
Flame-retardant cables can be made flame-retardant by adding flame retardants to the base polymer. During combustion, the flame-retardant components act in different ways and mechanisms to inhibit the free radicals that propagate chain growth in the polymer combustion reaction. The flame retardant captures free radicals in the gas-phase combustion zone, reducing the flame density and ultimately slowing the combustion reaction until it terminates.
2. Condensed-phase flame retardancy: This prevents the thermal decomposition of polymers and the release of flammable gases in the solid phase. At high temperatures, the flame retardant forms a molten glassy substance or a foamy carbon layer that covers the polymer surface, insulating it from heat and oxygen and preventing the escape of flammable gases.
3. Heat interruption: This removes heat generated by the polymer rather than feeding it back into the polymer, causing it to decompose. At high temperatures, the flame retardant undergoes a strong endothermic reaction, lowering the surface temperature of the combustible material. Heat releases non-combustible gases, which dilute the flammable gases released by the decomposition of the combustible material.
4. Carbonization: This generates char during thermal degradation of the polymer, reducing the production of volatiles. The sticky carbon layer covers the polymer surface, insulating it from flames.
Advantages and Disadvantages of Commonly Used Flame Retardants
1. Antimony-Based Flame Retardants
Advantages: Antimony trioxide cannot be used alone as a flame retardant, but when combined with appropriate halogen compounds, it exhibits particularly effective flame retardant properties.
Disadvantages: Heavy metals, toxic, homologues of arsenic; crude products often contain arsenic and other heavy metals.
II. Aluminum Hydroxide Flame Retardant (ATH)
Advantages: Low price, excellent flame retardancy.
Disadvantages: Poor heat resistance. Dehydration begins at 200°C and is completely dehydrated between 330°C and 350°C. Resin curing occurs mostly within the aluminum hydroxide dehydration temperature range, resulting in foaming in the finished synthetic resin, uneven surfaces, reduced dielectric properties, and low yield. High-temperature application can cause fogging of the silicone, whitening and blistering of the product, and reduced dielectric properties. EC value is approximately 60-100 μS/cm, and it is highly hygroscopic.
III. Magnesium Hydroxide Flame Retardant
Advantages: Magnesium hydroxide flame retardant (decomposes at 430°C) is non-toxic.
Disadvantages: Not acid-resistant; acetic acid can dissolve magnesium hydroxide, making it suitable only for low-end products. It is highly hygroscopic, has poor dispersion, and has poor dielectric properties.
IV. High-Heat-Resistant Boehmite Flame Retardant (Boehmite, ALOOH)
Advantages: 1% dehydration temperature reaches over 350°C, peaking at 500°C. EC <50μS/cm. Strong dielectric properties, addressing the issues of aluminum hydroxide's low dehydration temperature, which can lead to product defects and reduced dielectric properties. Strong acid and alkali resistance.
Disadvantages: Flame retardancy is slightly lower than aluminum hydroxide, requiring more additives to achieve the same flame retardancy. However, it offers high heat resistance, thermal conductivity, and acid and alkali resistance. Its use as a functional material with high heat resistance can enhance product value.
The article concludes with some additional information on flame-retardant power cables, specifically their applications. Flame-retardant power cables are used for the transmission and distribution of electrical energy. They are commonly used in urban underground power grids, power station outbound lines, industrial and mining enterprises, and other applications. Cables account for an increasing proportion of power lines, making it essential to have some knowledge about them.
