Expandable graphite and expanded graphite

Expandable graphite crystal is a typical carbon material with a layered structure. Other heterogeneous particles such as atoms, molecules, ions, and even radicals are inserted into the interlayer of crystalline graphite by physical or chemical methods to generate a new layered compound called graphite interlayer compound, which can expand graphite. Expandable graphite and expanded graphite are not the same, do the sealing strip to choose expanded graphite.

Expandable graphite is natural flake graphite(or artificial graphite with a high degree of graphitization), interlayer compound treated by an acidic oxidant (sulfuric acid, nitric acid, and hydrogen peroxide, potassium permanganate), also known as graphite oxide. The immersion of the oxidizer also causes small expansion behavior of the original graphite, and the interval between layers increases from 3.35A to 6-11A. The important characteristic of graphite oxide is that it has strange expansibility and can be expanded at high temperature, so it is expandable graphite;

Due to the adsorption properties of organic and biological macromolecules, expandable graphite has a wide application prospect in biomedical materials.

Fireproof sealing strip because of the expansibility of expandable graphite and its high-temperature resistance, expandable graphite becomes an excellent sealing material and is widely used in fireproof sealing strips. There are two main forms: the first is the inflatable graphite material and rubber material, inorganic flame retardant, accelerator, vulcanizing agent, reinforcing agent, filler mixing, vulcanization, molding, made of various specifications of expansion sealing rubber strip is mainly used for fire doors, fireproof glass Windows and other occasions.

This expansion sealing strip can block smoke flow from beginning to end at room temperature and fire. The other is glass fiber tape as the carrier, will be able to expand graphite with some adhesive bonding on the carrier, this adhesive formed at high temperature of the carbonization provided by the sheer force can effectively prevent graphite sliding. It is mainly used for fire doors, but it can not effectively block the flow of cold smoke at room temperature or low temperature, so it must be used with room temperature sealant.

Different from graphite, graphite oxide in external forces, such as ultrasonic under the action of water or alkali water can form better stability of graphite oxide colloidal or suspension, at the same time by the electrostatic repulsion of interlayer charge, graphite oxide layer-layer stripping. Expanded graphite is graphite oxide at a high temperature of 960-980℃, the rapid gasification and decomposition of compounds between the graphite layers, resulting in a certain amount of thrust, destroy the molecular force between the graphite layers, so that the C-C bond between the graphite lattice fracture, the layer expands rapidly along the C-axis direction, the layer spacing increases 50-500 times, from the compact scaly graphite, It becomes fibrous flock-like vermicular graphite;

Expanded graphite mainly produces graphite paper, processing all kinds of graphite gasket sealing materials, also known as flexible graphite, has the advantages of high-temperature resistance, high-pressure resistance, good sealing and corrosion resistance of a variety of media, is a new advanced sealing material. The thermal conductivity of expanded graphite is high, and flexible graphite can be used as thermal conductive material and conductive material. Therefore, can not be used to make fire door sealing strips.

The surface of expanded graphite has a certain charge. Using its charged properties, Bai Wuxianzhi synthesized a pmMA-graphite composite using an H2SO3 aqueous solution as an initiator. In addition, by using this polymerization method, the influence of a series of factors such as mixing time and mixing temperature on electrical conductivity can be avoided.