Why Is The Flame Retardant "Magnesium Hydroxide" So Great?

Why Is the Flame Retardant "Magnesium Hydroxide" So Great?

Flame retardant is a kind of additives that can improve the flame retardancy, self-extinguishing or smoke elimination of flammable or combustible materials. With the continuous expansion of the application fields of polymer materials, the flame retardant technology has also attracted more and more people's attention. Generally speaking, flame retardants can be divided into organic and inorganic categories, in the plastics industry, inorganic flame retardants due to good thermal stability, no volatilization, no precipitation, no corrosive toxic gases and other advantages, in recent years, rapid development. Among the inorganic flame retardants, magnesium hydroxide is a popular inorganic flame retardant developed in recent years because of its multi-functions such as flame retardant, smoke elimination, anti-dripping and filling.

I. Classification of magnesium hydroxide

Magnesium hydroxide can be divided into mechanical grinding method (also known as water magnesite) and chemical synthesis method according to the production method, in which the production capacity of mechanical grinding method is 300,000-500,000 tons, mainly concentrated in the Liaoning area. Chemical synthesis method can be divided into hydrothermal method, precipitation method, magnesium oxide hydration method and so on. Magnesium hydroxide flame retardant is mainly used in all kinds of rubber and plastic fields, of which the largest amount is still the ultrafine magnesium hydroxide prepared by mechanical grinding method.

Ultrafine magnesium hydroxide is a class of inorganic flame retardant made from natural magnesite minerals by ultrafine powder and certain surface treatment. Magnesite produced by magnesite magnesium hydroxide flame retardant, the source of natural minerals, processing the whole process is basically zero emission, it can be said that from the source to the product are in line with the requirements of greening, are non-toxic and harmless, environmentally friendly flame retardant, so known as “green environmental protection flame retardant”, has a huge market application prospects.

II. Introduction of Magnesite

The main component of magnesite is magnesium hydroxide, which is one of the minerals with high magnesium content in nature, the theoretical composition is: MgO 69.12%, H2O 30.88%. Water magnesite belongs to the tripartite crystal system, common flaky aggregates, sometimes into fibrous aggregates, its solution surface is pearl luster, hardness 2.5, specific gravity 2.3~2.6g/cm³.

China is a large country of magnesium resources, magnesium hydroxide flame retardant has unique resource advantages and good market prospects. According to statistics, water magnesite national reserves of about 25 million tons, of which: Fengcheng, Liaoning Province, Kuandian water magnesite deposits reserves of 10 million tons, is currently the world's largest water magnesite mines found; Shaanxi Heimulin (reserves of about 7.8 million tons), Jilin Ji'an (reserves greater than 2 million tons); In addition, Henan Xixia, Qinghai Qilianshan, Sichuan Jianshibao, and other places are also found in the water magnesite deposits.

III. Flame retardant mechanism of magnesium hydroxide flame retardant

Inorganic flame retardants generally play a flame retardant role in the gas phase or condensed phase. For ultrafine magnesium hydroxide flame retardant, its flame retardant mechanism can be summarized as follows:

1. Cooling effect

Magnesium hydroxide will decompose when heated, absorbing a large amount of latent heat, thereby reducing the actual temperature of the polymer surface, slowing down the polymer cracking speed, reducing the generation of combustible materials.

2. Dilution effect

Magnesium hydroxide in the heat of combustion at the same time releases a large amount of water vapor, water vapor is a non-combustible gas, can play a role in diluting combustible gases and the role of the surface of the oxygen, which makes the combustion can not be continued, to play the effect of gas-phase flame retardant. At the same time, magnesium hydroxide flame retardant in the polymer system in the filling amount are larger, to a certain extent, can also dilute the concentration of combustible materials in the solid phase, thus improving the flame retardancy of products.

3. Insulation effect

Magnesium hydroxide decomposition after heat to generate a layer of magnesium oxide dense layer, magnesium oxide is a class of excellent refractory materials, covering the surface of the polymer can improve the polymer resistance to flame, to play the purpose of preventing the combustion of the air isolation. The decomposition of magnesium oxide is also conducive to the polymer surface into carbon, carbon layer is also a class of excellent insulation layer.

4. Smoke suppression effect

Magnesium hydroxide flame retardant effect mainly occurs in the solid degradation area of the outer layer of the solid degradation area and pre-combustion area of the role is very small, which makes the combustible material combustion is not affected, so the smoke produced is relatively small. And magnesium hydroxide outer layer of the smoke released by combustion will also be decomposition of the water vapor produced by the dilution or absorption, so play a better role in smoke elimination.

In conclusion, it can be seen, magnesium hydroxide is a class of additive high-efficiency flame retardant, with flame retardant, smoke, anti-drip, filler and other multiple functions, not only can neutralize the acidic corrosive gases produced in the combustion process, but also does not emit hazardous substances, it is a kind of green environmentally friendly flame retardant.

IV. Advantages of magnesium hydroxide flame retardant

Because magnesium hydroxide has good thermal stability, does not produce corrosive gases, does not volatilize, has a long-lasting effect, no toxicity, and is inexpensive. At the same time with aluminum hydroxide than, it thermal decomposition temperature is high, in the flame retardant mechanism, decomposition capacity, heat capacity, carbonization, smoke suppression capacity, hardness, production costs, etc. have obvious advantages. Specifically:

1. The decomposition energy of magnesium hydroxide (1137 kJ/g) is higher than that of aluminum hydroxide (1117 kJ/g), and the heat capacity is also 7% higher, which helps to improve the flame retardant efficiency.

2. The hardness of magnesium hydroxide is lower than that of aluminum hydroxide, and the wear and tear on the equipment during processing is less, which can extend the service life of the equipment.

3. The thermal stability of magnesium hydroxide is better than aluminum hydroxide. Magnesium hydroxide decomposition temperature is higher, about 340 ℃; while the decomposition temperature of aluminum hydroxide is 220 ℃, so magnesium hydroxide can withstand higher processing temperatures, which is conducive to speeding up the extrusion speed, especially for the processing of polymers with higher temperatures.

4. Magnesium hydroxide is a kind of additive and efficient smoke suppressant flame retardant, compared with aluminum hydroxide and other similar inorganic flame retardant, it has better smoke suppression effect.

5. Experimental studies have shown that magnesium hydroxide is better than aluminum hydroxide in promoting the effect of polymer surface carbonization, thus the flame retardant effect is better than aluminum hydroxide.

With the increasing call for environmental protection, the world's flame retardant development field presents a trend of non-halogenation and low smoke, making the main body of magnesium hydroxide inorganic flame retardant consumption is rising rapidly.

V. Comparison of the Advantages and Disadvantages of Aluminum Hydroxide and Magnesium Hydroxide as Flame Retardants

Aluminum hydroxide has some drawbacks as a flame retardant. It usually needs to be added in large quantities (over 60%) for effective fire resistance, which can significantly change the physical properties of the material, such as reducing tensile and bending strength. It can also make processing more difficult by increasing material viscosity and reducing fluidity. Moreover, aluminum hydroxide has a relatively low decomposition temperature of around 220°C, so it may break down early in high - temperature situations, affecting the material's heat resistance and stability.

In comparison, magnesium hydroxide has a higher decomposition temperature of about 340°C, making it better for high - temperature processing. Its heat of decomposition and heat capacity are both superior to aluminum hydroxide's, allowing it to cool polymer surfaces more effectively. It also does a better job of reducing smoke during combustion. However, magnesium hydroxide has a high oil absorption value and doesn't mix well with polar resins, which can weaken the material's mechanical properties. It also tends to absorb moisture and needs to be protected from humidity during storage. Aluminum hydroxide, on the other hand, is less expensive and easier to process, but it's not as effective as magnesium hydroxide in suppressing smoke and heat.

VI. Application of magnesium hydroxide flame retardant

Magnesium hydroxide, as a kind of green and environmentally friendly flame retardant, is widely used in PVC, polyethylene, EPDM rubber and unsaturated polyester, and is a low-smoke halogen-free flame retardant, smoke suppressant and filler for conveyor belts, ventilation ducts, wire and cable sheathing, flame-retardant aluminum-plastic panels, flame-retardant plastic flooring and fire-resistant coatings for coal mines.

1. Wire and cable (PVC)

China is a big country of PVC cable, of which, flame retardant cable accounts for about 60% of the cable products. pvc combustion will decompose, and accompanied by toxic hydrogen chloride and other acidic gases emitted, which may cause major casualties, and magnesium hydroxide flame retardant is used to fill the polyvinyl chloride, which can adsorb the toxic gases. After adding magnesium hydroxide, the oxygen index of the product system rises, while the burning speed and the amount of smoke decreases significantly, giving the product flame retardant, smoke and high temperature resistance and other superior features. In addition, it can also improve the mechanical properties, processing performance and electrical properties of composite materials.

2. Pipe & Profile (Polypropylene)

Due to the flammability of polypropylene polymers, highly efficient flame retardants are usually added to the formulation of flame retardant grade polypropylene. At the same time, the processing temperature of polypropylene usually exceeds 200℃, and magnesium hydroxide flame retardant can be fully comparable and is the best choice for processing this type of product. By choosing the appropriate magnesium hydroxide flame retardant, not only can improve the flexural strength and flexural modulus of the product, improve the heat resistance of the product, but also meet the flame retardant requirements.

3. Polyolefin compounds (HFFR)

Polyolefin compounds are gradually replacing PVC-based compounds, and are widely used in areas with stringent requirements for smoke and toxic emissions, especially underground pipelines, public places, insulated wires and cables, and other areas. These materials are processed and produced at high temperatures, up to 300°C. The materials are also used in the production of electrical appliances. As a result, many polyolefin producers rely on magnesium hydroxide as a flame retardant to produce a dense end product. Magnesium hydroxide improves the processability of the product, has excellent mechanical properties and high thermal stability.

4. Cross-linked polyethylene (XLPE)

Cross-linked polyethylene is considered a good material in many insulation and piping fields. The high temperature of this material during processing makes magnesium hydroxide the flame retardant of choice, and magnesium hydroxide improves the thermal stability of the product and enhances the surface gloss and brightness.

5. Rubber

Rubber products, including conveyor belts used in the mining industry and hoses in utilities. Rubber alone is a very flammable substance, so all rubber products must be formulated to include flame retardants, and some neoprene rubbers become even more hazardous due to the large amounts of hydrogen chloride gas that can be released during combustion, making fires even more dangerous. Magnesium hydroxide adsorbs the toxic gases and provides a good smoke suppression effect, giving it excellent flame retardancy.

6. Silicone

Silicone is used in products such as seals, gaskets, and cables for electronics and electrical appliances. However, the high flammability of silicone makes it necessary to add flame retardant components, magnesium hydroxide flame retardant is the most suitable product in this regard.

7. Flooring & Wallboard

Wall panels and floors commonly available in the market today are generally based on PVC or polyethylene substrates. To create a safe home environment, flame retardants are usually added to PVC-based flooring materials. Magnesium hydroxide flame retardant can effectively reduce smoke and absorb acidic gases. The vertical nature of wallboard, which can easily cause vertical combustion, coupled with the base being a polyethylene polymer, makes it even more necessary to use magnesium hydroxide flame retardant to retard the fire. Magnesium hydroxide can improve the gloss and hardness of the products, and improve the heat resistance and flame retardancy of the products.

8. Fireproof coating

Thermal decomposition of magnesium hydroxide dehydration temperature between 420 ~ 520 ℃, the temperature and organic combustion temperature is close to, so can be used as a fire retardant fireproof coating. When filled into the fireproof coating, in the fire or even under the action of continuous flame, magnesium hydroxide will not decompose into gas compounds and burned away, its high stability, can play a long-lasting flame-resistant role, so that the fireproof coating has a highly efficient thermal insulation and fire performance.

9. Copper cladding board

Magnesium hydroxide in the application of copper-clad plate can meet the high heat resistance requirements of the products, giving products excellent electrical insulation properties, and make it better compatibility with the resin, for improving the surface and mechanical properties of the copper-clad plate has obvious effect. Hydroxide flame retardant efficiency, smoke suppression ability, small hardness, small friction on the equipment, help to extend the life of the equipment.

10. Electrical parts (polyamide)

Most insulators, switches, plugs and sockets must meet the most stringent fire protection standards. The addition of magnesium hydroxide in the formulation of polyamide products improves the processing fluidity of the products, excellent appearance, gives them good electrical and physical properties and excellent thermal stability.

11. Other applications

Magnesium hydroxide is often used as additive flame retardant or flame retardant filler in adhesives, and can be applied to the manufacture of magnesium salts, activated magnesium oxide, fine ceramics, thermal insulation materials, sugar refining, flue gas desulfurization agent, oil anticorrosive additives, wastewater neutralizing agent and so on.

In conclusion, magnesium hydroxide flame retardant stands out as a top choice in the field of fire safety due to its multifunctional advantages, including flame retardancy, smoke suppression, anti-drip properties, and filling functions. Its environmentally friendly nature and wide range of applications make it highly suitable for polymers in today’s world where environmental protection is increasingly emphasized. YINSU Flame Retardant Company, specializing in the R&D of eco-friendly flame retardants, offers a variety of products such as superfine coated ADP, superfine high-dispersible MCA, microencapsulated red phosphorus flame retardants, and halogen-free efficient flame retardants. These products are designed to meet diverse market demands, particularly in adhesive, coatings and other applications, providing excellent flame retardant performance while ensuring environmental compliance and material compatibility.