Magnesium hydroxide: the core breakthrough of flame retardant performance of fireproof aluminum-plastic panels

As a common material for building curtain walls and interior decoration, the polyethylene core layer of aluminum-plastic panels is easy to melt and drip at high temperatures, which accelerates the spread of fire and has long plagued the industry. In recent years, magnesium hydroxide (Mg(OH)2) has become a core material to ｒｅｐｌａｃｅ traditional halogen flame retardants with its unique "physical-chemical" synergistic flame retardant mechanism. This article will analyze its core role from three aspects: mechanism, performance verification and technological breakthrough.

1. Triple flame retardant mechanism: closed-loop protection from heat absorption to isolation

1. Heat absorption and cooling: the cornerstone of physical flame retardancy

When the temperature of the core layer of the aluminum-plastic panel reaches 340℃, magnesium hydroxide decomposes:

Mg(OH)2340∘CMgO+H2O

The reaction absorbs up to 1.316 kJ/g of heat

, significantly reducing the surface temperature of the material and making the temperature of the polyethylene core layer lower than the ignition point (usually 350-400℃). Compared with traditional halogen flame retardants, its heat absorption efficiency is increased by 25%, effectively slowing down the thermal degradation rate of polymers.

2. Gas phase isolation: the key to chemical smoke suppression

The water vapor released by the decomposition of magnesium hydroxide has a dual effect:

· Dilution effect: The volume of water vapor expands by about 1,700 times, diluting the oxygen concentration in the combustion area from 21% to below 15% (below the critical value for maintaining combustion);

· Free radical inhibition: Water molecules combine with active free radicals (such as ·OH, ·H) in the combustion chain reaction to interrupt the flame propagation path. Experiments show that when aluminum-plastic panels containing 30% magnesium hydroxide are burned, the free radical concentration drops by 60%.

3. Solid phase barrier: guarantee of long-term protection

The decomposed magnesium oxide (melting point 2852℃) forms a dense ceramic protective layer on the surface of the material:

· Physical isolation: The thermal conductivity of the magnesium oxide layer is only 0.07 W/(m·K), which blocks more than 80% of heat transfer;

· Catalytic carbonization: Magnesium oxide promotes the pyrolysis of polyethylene to generate a graphitized carbon layer. The thickness of the carbon layer can reach 2-3 mm in the vertical combustion test, which shortens the self-extinguishing time of the aluminum-plastic plate to less than 5 seconds (the national standard requires ≤30 seconds).

2. Performance verification: the leap from laboratory to industrialization

1. Flame retardant efficiency and environmental protection characteristics

The actual measured data of a building materials company shows

:

· Oxygen index: increased from the national standard 30 to 38, reaching the A2 fire protection standard;

· Smoke suppression performance: The smoke density level is reduced from more than 10 of traditional materials to 2, a decrease of 80%;

· Environmental certification: Passed the EU REACH certification, the combustion products are only CO2 and H2O, and no halogen gas is released.

2. Economic efficiency and processing optimization

· Cost control: Although the unit price of magnesium hydroxide is higher than that of aluminum hydroxide, its addition amount can be reduced by 20% (typical formula is 40%-60%), and the overall cost is reduced by 15%;

· Process improvement: Silane coupling agent surface modification technology is used to solve the dispersion problem of magnesium hydroxide in the polyethylene matrix, and the interlayer peeling strength is increased by 35%.

III. Technological breakthrough: from material modification to system innovation

1. Surface modification technology

The high filling amount of magnesium hydroxide (>50%) is prone to deterioration of hygroscopic interface. Optimization through the following schemes:

· Nano-coating: Form a hydrophobic layer on the surface of the particles to reduce moisture adsorption;

· Compounding and synergistic effect: Used in conjunction with hydrophobic flame retardants such as zinc borate, the total addition amount is reduced by 30%, while improving the flame retardant efficiency.

2. Improved processing fluidity

Traditional ultrafine magnesium hydroxide is easy to agglomerate, which affects extrusion molding. The microemulsion method is used to prepare powders with controllable particle size (1-5μm), improve processing performance, optimize processing temperature from 180℃ to 150℃, and reduce energy consumption by 20%.

IV. Future trends: intelligent and multifunctional integration

1. Dynamic flame retardant system

Combined with AI algorithm to monitor the combustion state in real time, the thermal response characteristics of magnesium hydroxide are regulated by doping transition metal oxides (such as Fe2O3) to achieve dynamic matching of decomposition rate with fire intensity

2. Multifunctional composite materials

Magnesium hydroxide is compounded with graphene to give aluminum-plastic panels antistatic and electromagnetic shielding functions while being flame retardant, expanding its application in 5G base stations, data centers and other scenarios.

Magnesium hydroxide not only solves the flammable defects of traditional aluminum-plastic panels through the triple synergistic mechanism of "heat absorption-smoke suppression-isolation", but also promotes the industry to green upgrade with its environmental protection characteristics. With the maturity of technologies such as surface modification and intelligent regulation, this material is expected to fully ｒｅｐｌａｃｅ toxic flame retardants in fields such as construction and transportation, leading fireproof materials into a new era of high performance and sustainable development.