Expandable Graphite
Size
0.50mm or 0.106mm, etc
Package
25 kg small bags into ton bags
Origin
China
Features
Preservative/Electrical and thermal conductivity, etc.
Application
Fireproof sealing element, flame retardant, refractory brick, etc.
Expandable graphite crystal is a typical layered carbon material. Other heterogeneous particles such as atoms, molecules, ions, and even atomic clusters are inserted into the interlayer of crystalline graphite by physical or chemical methods to form a new layered compound, which is called graphite interlayer compound, namely expandable graphite.
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Expanded graphite is also called flexible graphite. It is mainly a compound formed by chemical treatment of flake graphite as a raw material. The compound turns into gas at a high temperature of 800-1000 ° C, causing natural flake graphite to expand about 200 times. It can be used under harsh conditions. , There will be no decomposition, deformation or aging.
Expanded graphite has no radiation and no pollution, and it does not contain toxic substances. Unlike other asbestos products, it is harmful to the human body and pollutes the environment. It is resistant to high temperatures and can withstand high temperatures of 1650°C. Under such high temperature conditions, even if chemical equipment melts, it will be safe and sound.
The use of expanded graphite
(1) Expanded graphite has a wide range of applications. It can withstand most chemical media, including radioactive chemical media, in the case of strong oxidizing acids. It has relatively poor adaptability to asbestos products. Not only can it not be used in radioactive media, chemical For towers, heat exchangers, etc., it is required that the connection parts cannot be insulated, but expanded graphite can achieve this effect.
Expanded graphite is easy and quick to use, and its gasket coefficient is only half of that of asbestos products, resulting in a better sealing effect, so the force on the screw does not need to be too large. Expanded graphite has excellent sealing performance, compressibility, good elasticity, and oxidation resistance. Features, strong self-lubricating and plasticity,
(2) Expanded graphite also has the characteristics of good electrical conductivity, high specific gravity, and high density. It can be used to make various types of compressors and other pipes, flange gaskets, etc.
The ways to make expanded graphite
1. Chemical intercalation method: The initial raw material for preparation is Qingdao Huatai natural flake graphite, and other chemical reagents such as concentrated sulfuric acid (above 98%), hydrogen peroxide (above 28%), and potassium permanganate are all used industrial grade reagents .
The general steps of preparation are as follows: at an appropriate temperature, react hydrogen peroxide solutions of different proportions, natural flake graphite and concentrated sulfuric acid with different addition procedures under constant stirring for a certain period of time, then wash with water until neutral, and centrifuge. After dehydration, it was vacuum-dried at 60 °C.
2. Electrochemical method: Treat graphite powder in a strong acid electrolyte to make expandable graphite, hydrolyze, wash and dry. Sulfuric acid or nitric acid is mainly used as strong acid, and the expandable graphite produced by this method has a low sulfur content.
3. Ultrasonic oxidation method: In the process of preparing expandable graphite, ultrasonic vibration is performed on the anodized electrolyte. The time of ultrasonic vibration is the same as the time of anodic oxidation. Because the vibration of the ultrasonic wave on the electrolyte is beneficial to the polarization of the cathode and anode Effect, thereby speeding up the speed of anodic oxidation and shortening the oxidation time.
4. Gas phase diffusion method: Apply graphite and intercalation to both ends of a vacuum-sealed tube, heat at the end of the intercalation, and use the temperature difference between the two ends to form the necessary reaction pressure difference, so that the intercalation enters in the state of small molecules Expandable graphite is produced between the flake graphite layers. The number of layers of expandable graphite produced by this method can be controlled, but its production cost is high.
5. Molten salt method: Mix and heat several inserts with graphite to form expandable graphite. Graphite crystals have a hexagonal network planar layered structure composed of carbon elements. Therefore, under appropriate conditions, acids, alkali metals, A variety of chemical substances such as salts can be inserted between graphite layers and combine with carbon atoms to form a new chemical phase – graphite interlayer compound.
When this interlayer compound is heated to an appropriate temperature, it can decompose rapidly in an instant, producing a large amount of gas, which makes the graphite expand into a worm-like new substance along the axis, that is, expanded graphite. This unexpanded graphite interlayer compound is expandable graphite. graphite.
