Since graphite is a non-polar materials, alone small polar organic or inorganic acid intercalation difficult, generally must use oxidants. Chemical oxidation is generally immersed in the natural flake graphite intercalation agent and the oxidizing agent solution, under the action of strong oxidizing agents, graphite is oxidized leaving the neutral plane macromolecular mesh graphite layer becomes positively charged plane macromolecules, since the repulsion between the positively charged layer plane macromolecules homosexual positive charge, increase the distance between the graphite layers, intercalation agent inserted between the graphite layers, become expandable graphite.
Expandable graphite prepared discretion chemical oxidation process requires the use of an oxidizing agent. Oxidant chemical oxidation using generally solid oxidant and a liquid oxidant categories. Solid oxidant KMn04, KCI04, NaCl03, (NH4) 2S207 like liquid oxidant H2S04, HNO3, HCIO4, H202 and so on. Generally solid oxidizer violent reaction, dangerous, high prices, product ash content, and pollute the environment. Liquid oxidant H2S04, HNO3 and other deterioration of the operating environment, water pollution, H202 mild reaction, less pollution.
For expandable graphite, the expansion volume and sulfur content are two important indicators of the product, it is generally desirable expansion volume high and low sulfur content. Expandable graphite corrosive effect of sulfur in the application will have equipment, the traditional use of H2S04 expandable graphite intercalation agent and as an oxidizing agent, the sulfur content is often too high (such as 3% to 4%), can not meet the flexible graphite and other important areas of application requirements. So in recent years, low-sulfur and sulfur-free expandable graphite expandable graphite, particularly sulfur-free expandable graphite Expandable Graphite has become an important direction of research and development, researchers have done a lot of work and achieved breakthrough results. Further, conventional expandable graphite generally to swell more than 200 times at a high temperature 900-1000 ℃, in some applications want their expansion in multiples of 200 times or more puffed lower the temperature the better, so the recent low temperature expandable graphite expandable graphite has become the research and development of a new direction.