How to Prepare Expandable graphite

Expandable graphite is produced by two common preparation methods in the Franli factory: natural flake graphite is used as raw material, firstly oxidized to obtain expandable graphite, and then expanded to obtain expanded graphite; the explosion method that oxidizes and expands at the same time. As a new type of carbon functional material, it has many special properties and can be widely used in electrode materials, petrochemicals, fire-retardant, oil-absorbing materials, environmental protection, medical dressings, military smoke-generating agents and anti-static coatings. It has many advantages such as good chemical stability and high temperature resistance.

Manufacture of Expandable graphite by Oxidation

If want to produce expandable graphite, it can be made through 2 common methods.

(1) Chemical oxidation method: Graphite is oxidized by an oxidant, so that it loses electrons, the edge of graphite can be opened, and the intercalation agent can enter between the graphite layers, thereby forming a graphite interlayer compound. Due to the stable chemical properties of natural flake graphite, only strong oxidants can be used to oxidize natural flake graphite. Commonly used solid oxidants are KMnO4, K2CrO7, NaNO3, KClO4 and (NH4) 2S2, etc., and commonly used liquid oxidants are HClO4, H2O2, HNO3, etc. Since sulfuric acid molecules have the strongest ability as an intercalating agent, sulfuric acid is used as an intercalating agent in the preparation of expandable graphite by traditional methods. The traditional chemical oxidation method is simple in process and stable in quality, but there are problems such as waste of acid solution and high sulfur content in the product.

(2) Electrochemical method: Using the electrical conductivity of graphite, the raw graphite is oxidized between layers under the action of anode current, and acid ions are inserted between the graphite layers to obtain expandable graphite. Taking the organic-inorganic acid solution system as the medium, using the acetic acid-sulfuric acid mixed solution as the electrolyte, the graphite is electrochemically treated in the electrolytic cell to obtain the expandable graphite.

The Franli factory uses perchloric acid-acetic acid mixed acid as electrolyte, and the current density is 0.06 A·cm-2, and the intercalation effect of expandable graphite is good. The electrochemical method does not use an oxidant, and the acid solution can be recycled and reused many times, with little environmental pollution and low cost, but the yield is low, and the requirements for electrode materials are relatively high. Currently, it is limited to laboratory research.

Explosive production of expandable graphite

The preparation of expandable graphite by the explosion method can make the oxidation intercalation and the expansion process to be carried out at the same time. The specific operation is to use Mg(ClO4) 2·nH2O, HClO4 or Zn(NO3) 2·nH2O as the expansion agent to mix with the raw graphite, and the mixture simultaneously With oxides and intercalators, when heated, it will produce “explosive” expansion to obtain expanded graphite. Different bulking agents lead to different properties of the obtained expanded graphite. When HClO4 is used as an expansion agent, only expandable graphite can be prepared by the explosion method. When metal salts such as Mg(ClO4) 2·nH2O or Zn(NO3) 2·nH2O are used as expansion agents, in addition to expanded graphite, metal can also be prepared. The presence of oxides, metal oxides can make expandable graphite surface modification. The explosion method is simple to operate, takes less time, but has low purity, is difficult to control, and is rarely used.

Franli factory adopt some new ways to make preparation of expandable graphite for such reasons such as environmental protection and energy saving. The future development direction is to use fine flake graphite as raw material, saving raw materials or other metal raw materials.