The problem of burning and dripping of aluminum-plastic panels: the inhibition mechanism of brucite powder

Aluminum plastic panels are widely used in building exterior wall decoration materials due to their advantages of lightweight, beauty, and convenient construction. However, in fire accidents, aluminum-plastic panels have exposed a serious problem - they are prone to producing molten droplets during combustion. These high-temperature droplets not only accelerate the spread of fire, but may also cause secondary harm to people and objects below.

How to effectively suppress the melting and dripping behavior of aluminum-plastic panels during combustion has become one of the key directions in the research and development of fire-resistant building materials in recent years. In this context, brucite powder, as a halogen-free and environmentally friendly flame retardant, has gradually demonstrated its unique advantages in alleviating the burning and dripping of aluminum-plastic panels.

1、 Why is aluminum-plastic panel prone to burning and dripping?

Aluminum plastic panels are usually composed of two layers of aluminum alloy sheets and a middle layer of polyethylene (PE) or modified polypropylene core material. In a fire, the plastic core material softens, melts, or even burns due to heat, causing the entire board structure to lose its support, resulting in deformation, cracking, and even complete detachment.

Even more dangerous is that plastic materials in a molten state will drip downwards under the action of gravity, forming flammable droplets. Once in contact with other combustibles, it is highly likely to trigger a secondary fire and expand the scope of the fire.

This phenomenon is particularly common in high-rise building facade fires, which has prompted relevant standards to continuously improve the requirements for the fire performance of aluminum-plastic panels, especially the assessment of the "combustion drip level" has become increasingly strict.

2、 The limitations of traditional flame retardants

In order to solve the problem of burning and dripping in aluminum-plastic panels, the early common practice was to add flame retardants such as aluminum hydroxide and decabromodiphenyl ether to the core material. However:

Although halogenated flame retardants can improve flame retardant efficiency, they release a large amount of toxic gases and black smoke during combustion, which does not meet modern environmental requirements;

Although aluminum hydroxide is a halogen-free and environmentally friendly material, its decomposition temperature is relatively low (about 200 ° C), which may cause partial dehydration reaction during the processing of aluminum-plastic panels, affecting the subsequent molding process;

More importantly, these traditional flame retardants have limited effectiveness in suppressing melt dripping.

Therefore, finding a new type of flame retardant material that can improve flame retardant performance and effectively suppress combustion dripping has become a technical difficulty that the industry urgently needs to solve.

3、 The unique advantages of brucite powder

The main component of brucite powder is magnesium hydroxide (Mg (OH) ₂), which is a functional filler obtained by crushing and purifying natural minerals. Compared to traditional flame retardants, it exhibits significant advantages in the following aspects:

1. High decomposition temperature and wide applicability

The thermal decomposition temperature of brucite powder is about 340 ° C, much higher than that of aluminum hydroxide, which means it can remain stable during the processing of aluminum-plastic panels and will not affect material properties due to premature dehydration.

2. Strong heat absorption effect, delaying the combustion process

During the heating process, brucite powder gradually releases crystalline water and absorbs a large amount of heat, thereby reducing the surface temperature of the material, slowing down the pyrolysis rate of the organic core material, and prolonging the ignition time.

3. Inhibit melt dripping and form a protective carbon layer

This is one of the key characteristics that distinguishes brucite powder from other flame retardants. When brucite powder decomposes under heat, the generated magnesium oxide (MgO) has good high temperature resistance and alkalinity, and can form a dense porous carbon layer on the surface of the material.

This layer of carbon film can not only isolate oxygen and delay flame propagation, but more importantly, it can wrap the molten plastic to prevent it from detaching from the board and dripping. In this way, even if the internal core material starts to burn, flammable droplets will not easily form, greatly reducing the risk of fire spread.

Experimental verification: Actual effect of brucite powder

Multiple research institutions and production enterprises have verified the application effect of brucite powder in aluminum-plastic panels through combustion testing. For example, in the vertical combustion test, the aluminum-plastic panel sample with an appropriate amount of brucite powder added exhibited the following characteristics:

The flame spread speed significantly decreases; Reduced combustion time; Almost no obvious melting dripping phenomenon is observed; The smoke density has significantly decreased, and the release of toxic gases has decreased. These data indicate that brucite powder not only improves the flame retardant level of aluminum-plastic panels, but more importantly, effectively solves the safety hazard of combustion dripping.

With the continuous improvement of building fire prevention standards, the problem of burning and dripping of aluminum-plastic panels has become a major bottleneck limiting their application. And brucite powder, with its excellent thermal stability, strong heat absorption ability, and unique anti drip mechanism, is gradually becoming an ideal choice to solve this problem.