After the expandable graphite is instantaneously treated at high temperature, the scale becomes worm-like, and the volume can expand 100-400 times. This expanded graphite still maintains the properties of natural graphite, has good expandability, is loose and porous, and is resistant to temperature under oxygen barrier conditions. Wide range, can be between -200 ~ 3000 ℃, chemical properties are stable under high temperature, high pressure or radiation conditions, in the dynamic and static sealing of petroleum, chemical, electrical, aviation, automobile, ship and instrumentation industries There are a wide range of applications. The following editors of Furuit Graphite will take you to understand the common production methods of expandable graphite:
1. Ultrasonic oxidation method to make expandable graphite.
In the process of preparing expandable graphite, ultrasonic vibration is performed on the anodized electrolyte, and the time of ultrasonic vibration is the same as that of anodization. Since the vibration of the electrolyte by the ultrasonic wave is beneficial to the polarization of the cathode and the anode, the speed of anodic oxidation is accelerated and the oxidation time is shortened;
2. The molten salt method makes expandable graphite.
Mix several inserts with graphite and heat to form expandable graphite;
3. The gas-phase diffusion method is used to make expandable graphite.
The graphite and the intercalated material are respectively brought to the two ends of a vacuum sealed tube, heated at the end of the intercalated material, and the necessary reaction pressure difference is formed by the temperature difference between the two ends, so that the intercalated material enters the flake graphite layer in the state of small molecules, thereby Prepared expandable graphite. The number of layers of expandable graphite produced by this method can be controlled, but its production cost is high;
4. The chemical intercalation method makes expandable graphite.
The initial raw material used for preparation is high carbon flake graphite, and other chemical reagents such as concentrated sulfuric acid (above 98%), hydrogen peroxide (above 28%), potassium permanganate, etc. are all industrial grade reagents. The general steps of preparation are as follows: at an appropriate temperature, the hydrogen peroxide solution, natural flake graphite and concentrated sulfuric acid of different proportions are reacted for a certain period of time under constant stirring with different addition procedures, then washed with water to neutrality, and centrifuged, After dehydration, vacuum drying at 60 °C;
5. Electrochemical production of expandable graphite.
Graphite powder is treated in a strong acid electrolyte to make expandable graphite, hydrolyzed, washed and dried. As the strong acid, sulfuric acid or nitric acid is mainly used. The expandable graphite obtained by this method has a low sulfur content.
Post time: May-27-2022