Hexagonal flake magnesium hydroxide: flame retardant upgrade with doubled specific surface area
In recent years, hexagonal magnesium hydroxide has become a hot topic in the research and application of new halogen-free flame retardants due to its unique morphology and significantly enhanced physical and chemical properties. Compared to traditional granular magnesium hydroxide, the hexagonal sheet-like morphology not only improves the thermal stability and decomposition efficiency of the material, but more importantly, its specific surface area is significantly increased, resulting in better flame retardant effect and processing adaptability.
1、 Structural characteristics of hexagonal magnesium hydroxide flakes
Magnesium hydroxide (Mg (OH) ₂) is a typical layered double hydroxide, naturally occurring in the form of brucite. By controlling specific synthesis processes, magnesium hydroxide crystals with regular hexagonal sheet-like structures can be prepared, known as "hexagonal sheet-like magnesium hydroxide".
The formation of this special morphology mainly depends on the difference in growth rate of different crystal planes during the crystal growth process. The hexagonal sheet-like structure has a large aspect ratio, a flat surface, clear edges, and presents a highly ordered layered stacking structure. It is this structure that endows it with a higher specific surface area and more uniform dispersion compared to conventional granular magnesium hydroxide.
2、 The performance leap brought by doubling the specific surface area
Specific surface area is an important parameter for measuring the surface area per unit mass of a material. For flame retardants, this indicator directly affects their interfacial bonding ability with the substrate and their reactivity during combustion.
Hexagonal sheet-like magnesium hydroxide, due to its thin layer structure and regular shape, can provide a larger contact area at the same addition amount. This not only helps to improve its dispersion uniformity in the polymer matrix, reduce agglomeration, but also effectively enhances its dehydration and heat absorption efficiency when heated. Specifically:
Higher dehydration efficiency: The hexagonal sheet-like structure increases the contact area with heat, allowing magnesium hydroxide to release crystal water faster during thermal decomposition, providing stronger cooling and dilution of combustible gases.
Better heat shielding effect: During combustion, the sheet-like structure is more likely to form a dense carbonized layer on the surface of the material, isolating oxygen and heat transfer, and delaying the spread of fire.
Enhanced mechanical properties: Due to the orientation and supporting effect of the sheet-like structure, it can play a role similar to "nano reinforcement" in composite materials, improving the strength and toughness of the material.
These advantages make hexagonal magnesium hydroxide exhibit potential superior to traditional products in terms of flame retardancy, processing performance, and finished product appearance.
3、 Application performance in polymer materials
At present, hexagonal magnesium hydroxide has been widely used in various polymer material systems, including polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), epoxy resin, rubber, etc. Especially in the wire and cable industry, its application effect is particularly prominent.
Taking low smoke halogen-free flame-retardant cable materials as an example, although traditional magnesium hydroxide has good flame-retardant properties, its large particle size and poor dispersion can easily lead to a decrease in mechanical properties of the material, and even problems such as "powder settling" or "precipitation". After adopting hexagonal sheet magnesium hydroxide, due to its higher specific surface area and better interface compatibility, not only does it improve flame retardant efficiency, but it also effectively improves the flexibility and tensile strength of the material.
In addition, in fields such as building insulation materials, electronic and electrical casings, and automotive interior parts that require high safety and environmental protection, hexagonal sheet magnesium hydroxide also demonstrates good adaptability. Its halogen-free, low smoke, and non-toxic characteristics fully comply with the current concept of green manufacturing and sustainable development.
4、 Production process and technical difficulties
It is not easy to achieve large-scale stable production of hexagonal magnesium hydroxide. Its synthesis usually adopts precipitation method, hydrothermal method or solvothermal method, and guides the crystal growth along a specific direction by precise control of parameters such as reaction temperature, pH value, type and concentration of additives.
The key lies in how to control the anisotropic growth of crystals and avoid the generation of irregular particles or spherical structures. At the same time, attention should be paid to maintaining the integrity of the sheet-like structure during the drying and crushing process to prevent performance degradation caused by external forces.
Although some enterprises have achieved industrial production of such products, further optimization and improvement are still needed in terms of batch consistency, cost control, and deep matching with downstream applications.
With the increasingly strict environmental regulations worldwide and the continuous improvement of end users' requirements for product safety, high-performance, halogen-free and environmentally friendly flame retardants are gradually replacing traditional halogenated flame retardants and becoming the mainstream choice in the market.
Hexagonal magnesium hydroxide, with its comprehensive advantages such as large specific surface area, high flame retardant efficiency, good mechanical properties, and green environmental protection, is gradually opening up application space in multiple fields such as high-end cables, new energy vehicles, rail transit, and aerospace.
Meanwhile, with the advancement of nanomaterial technology and surface modification processes, it is expected to further enhance its dispersibility and synergistic flame retardant effect in polymer matrices through functional treatment in the future, expanding its applications in emerging fields such as transparent flame retardant materials and flexible electronic packaging.