In cable manufacturing, the choice of flame retardant is crucial, directly impacting a cable's fire resistance, service life, and wide range of applications. The following will provide a comprehensive comparison of the advantages and disadvantages of four commonly used cable flame retardants: antimony-based flame retardants, aluminum hydroxide flame retardants (ATH), magnesium hydroxide flame retardants, and high-heat-resistant boehmite flame retardants (ALOOH).
1. Antimony-Based Flame Retardants
Advantages
Antimony trioxide alone is not effective as a flame retardant. However, when combined with appropriate halogen compounds, it exhibits exceptional flame retardancy. During combustion, this complex system undergoes a series of complex chemical reactions, producing flame-retardant substances that effectively suppress the spread of flames.
For example, in cable applications requiring extremely high fire protection, such as high-rise buildings and large data centers, combining antimony-based flame retardants with halogen compounds can significantly improve the cable's flame retardancy, providing a strong guarantee for fire safety.
Disadvantages
Antimony-based flame retardants pose significant environmental and health risks. Antimony is a heavy metal and is somewhat toxic. More seriously, it belongs to the same family as arsenic, and crude products often contain arsenic and other heavy metal impurities. Arsenic trioxide, better known as arsenic, is extremely toxic. With increasing global attention to environmental protection and human health, and the growing adoption of green manufacturing concepts, antimony-based flame retardants, due to their toxicity, fail to meet the requirements of green fillers and green flame retardants, and their application is gradually being limited.
2. Aluminum Hydroxide Flame Retardant (ATH)
Advantages
The greatest advantage of aluminum hydroxide flame retardant is its low price and excellent flame retardancy. It acts by absorbing heat and releasing water vapor during combustion, effectively reducing the temperature in the combustion zone and suppressing the spread of flames. For cost-sensitive cable products where flame retardancy is not a top priority, aluminum hydroxide flame retardant is an economical and affordable option.
Disadvantages
Poor heat resistance is one of the main drawbacks of aluminum hydroxide flame retardant. It begins to dehydrate at 200°C and is completely dehydrated between 330°C and 350°C. The resin curing process primarily occurs within the dehydration temperature range of aluminum hydroxide. This dehydration produces a large amount of gas during the curing process, causing internal foaming and surface unevenness in the finished synthetic resin product. This also significantly reduces dielectric properties, leading to a decrease in yield.
Under high-temperature conditions, when aluminum hydroxide is used in materials such as silicone, it can cause problems such as fogging, whitening and blistering, and a decrease in dielectric properties. Furthermore, aluminum hydroxide has a relatively high electrical conductivity (EC) of approximately 60-100 μS/cm, and is susceptible to moisture absorption. These characteristics hinder its use in cables with high performance requirements.
3. Magnesium Hydroxide Flame Retardant
Advantages
Magnesium hydroxide flame retardant is non-toxic and has a relatively high decomposition temperature of 430°C. It can be an option in cable applications with stringent environmental requirements and certain heat resistance requirements. For example, the use of magnesium hydroxide flame retardants in some indoor low-voltage cables can ensure certain flame retardant properties while reducing environmental pollution.
Disadvantages
Magnesium hydroxide flame retardants have poor chemical stability and are not acid-resistant. Even weak acids such as acetic acid can dissolve them, significantly limiting their application to low-end products. Furthermore, they are susceptible to moisture absorption, have poor dispersibility, and exhibit suboptimal dielectric properties. During cable manufacturing, moisture absorption can lead to internal moisture buildup, impacting the cable's electrical performance and service life. Poor dispersibility can lead to uneven distribution of the flame retardant within the cable material, reducing its flame retardant effectiveness. Poor dielectric properties can also affect the cable's signal transmission quality.
4. High-Heat-Resistant Boehmite Flame Retardant (Boehmite, ALOOH)
Advantages
High-heat-resistant boehmite flame retardants offer numerous advantages. Its 1% dehydration temperature can reach over 350°C, reaching its peak dehydration rate at 500°C. This effectively addresses the issues of aluminum hydroxide, which can cause product defects and reduced dielectric properties due to low dehydration temperatures. Its electrical conductivity (EC) is less than 50μS/cm, and its strong dielectric properties ensure excellent electrical performance in cables even at high temperatures.
High-heat-resistant boehmite flame retardant also exhibits strong acid and alkali resistance, maintaining stable performance in a variety of harsh environmental conditions. Furthermore, it exhibits thermal conductivity, making it suitable for cable products requiring high heat resistance, electrical performance, and thermal conductivity, such as new energy vehicle cables and aerospace cables.
Disadvantages: The flame retardancy of high-heat-resistant boehmite flame retardant is slightly lower than that of aluminum hydroxide, requiring a higher dosage to achieve the same flame retardancy. This, in turn, increases production costs. However, given its many excellent properties, including high heat resistance, acid and alkali resistance, and thermal conductivity, as well as its ability to be made into high-heat-resistant functional materials to enhance product value, these disadvantages are relatively forgivable given its comprehensive advantages.