What is the differences between Brucite and precipitated MDH?

What is the differences between Brucite and precipitated MDH?

We all know that Brucite is the mineral form of magnesium hydroxide, and the chemical formula of Brucite and precipitated magnesium hydroxide(also know as MDH or MH) is the same—Mg(OH)2. However, when used as flame retardant there are some differences between these two materials. And in this passage, I would like to share with you some differences between Brucite and precipitated MDH. Kindly noted that precipitated magnesium hydroxide in this passage was manufactured according to the chemical reaction: MgCl2 + 2NH3 ▪ H2O → Mg(OH)2↓ + 2NH4Cl. 

1. Resources

The main resource of Brucite ore exists in Russia, America, Canada, China. And the Brucite ore in China is mainly located in Shanxi province, Liaoning province, Qinghai province, Sichuan province, Jilin province. 

The precipitated magnesium hydroxide gets its raw material from seawater, so the resource of precipitated MDH is more widespread than Brucite.

2. Purity and whiteness

Speak of the purity of Brucite and precipitated magnesium hydroxide, we have to talk about the production process of these two materials first of all. 

Because the Brucite mineral exists in nature, it contains many impurities such as CaO, SiO2, Fe2O3, etc. To improve the purity of Brucite powder, we need to go through several beneficiation processes first, including handpick and machine pick. And then the ore will go through a jaw crusher, Raymond mill, vertical mill, etc, to produce the different superfine powder. So the purity of Brucite is generally around 88%, 90%, 92%, and the whiteness is around 88%, 90%.

For the production of the precipitated MDH, first, we extract its main raw material directly from the salt lake to prepare the Magnesium Chloride solution, then the solution will go through a purification process to become a highly purified solution. And then add purified Magnesium Chloride solution and ammonium hydroxide into the reactor to react under a specific circumstance, chemical reaction: MgCl2 + 2NH3 ▪ H2O → Mg(OH)2↓ + 2NH4Cl. Finally, we will get rough precipitated magnesium hydroxide. Then go through the mill process to produce the super fine powder. Because the whole process uses a purified solution, so the purity of precipitated MDH is above 99%, and the whiteness is above 100%.

Click the link to check the whiteness difference between Brucite and precipitated magnesium hydroxide https://youtu.be/RBfv8xYrcl8

3. Dispersibility

From the perspective of dispersibility, natural Brucite is easily agglomerate compared with precipitated MDH. But we can decrease agglomeration by appropriate surface modification.

4. Price

Because the production cost of Brucite powder is cheaper due to simple processes, so the price of brucite powder is lower. However, there is a much more complicated process and more investment involved in the production of precipitated MDH, so the price for high purity MDH is higher. 

5. Application

Magnesium hydroxide has flame retardant, smoke suppression, high filling functions. Because magnesium hydroxide is an inorganic flame retardant, it has poor compatibility with polymer, so it can not disperse uniformly in polymer if the loading amount is high. To solve this problem, the manufacturer will do surface modification to magnesium hydroxide. For example, silane treated MDH benefits the fire performance of the EVA, particularly for highly MDH-filled compounds. Fatty-acid treated MDH can enhance compounding processing although it could reduce the physical and mechanical properties, especially with overly treated MDH. And when choosing the surface treatment to maximize the specific mechanical properties and performance, we have to consider the tradeoffs at acceptable levels.

There are no clear boundaries between the specific application of Brucite and precipitated magnesium hydroxide. The best way to decide whether to use Brucite or precipitated MDH in your product is by testing.

Based on my experiences, the application of Brucite powder includes low smoke flame retardant PVC compound (such as XK-1250SA/90, stearic acid coated brucite), Aluminum composite panel, flame retardant TPO waterproof membrane, cable bedding compound, etc…

The application of high purity precipitated magnesium hydroxide includes wire and cable, insulation cable compound, low smoke zero halogen polyolefin compound (such as XK-10000SN/99), etc…

6. Environmental friendly

Both Brucite powder and precipitated magnesium hydroxide are environmentally friendly as inorganic flame retardant. But what about the production process? Is it belong to green production?

The production of Brucite will not produce toxicity during processing. Because the content of SiO2, Al2O3, Na, and K in brucite is very low, and the content of water is very high, and the production of brucite mainly involves physical change. Besides, generally, the manufacturer will equip Dust removal equipment, so the whole process is relatively green.

The precipitated MDH is generated based on MgCl2 + 2NH3 ▪ H2O → Mg(OH)2↓ + 2NH4Cl reaction. The process follows below:

 “Configure the reaction bottom liquid–>heat the bottom liquid–>inject high-concentration magnesium chloride solution and ammonia gas–>stop the injection process after reaching a certain capacity–>filter” Each batch of products needs to repeat the above process continuously. 

We can see that the process uses ammonia as the precipitant. No new impurities are introduced, so the product contains low impurities. It is easy to obtain high-purity magnesium hydroxide. The tail liquid ammonia nitrogen treatment adopts commercial methods to meet environmental protection requirements, and the ammonia gas is recycled without environmental pollution.

We introduced the difference between Brucite and precipitated magnesium hydroxide from the perspective of resources, whiteness, purity, dispersibility, price, application, environmentally friendly, green production. If you have any questions about this passage, please feel free to contact author Elena at [email protected] Thank you for your time.

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