As a new functional carbon material, Expanded Graphite (EG) is a loose and porous worm-like material obtained from natural graphite flake by intercalation, washing, drying and high temperature expansion. EG In addition to the excellent properties of natural graphite itself, such as cold and heat resistance, corrosion resistance and self-lubrication, it also has the characteristics of softness, compression resilience, adsorption, ecological environment coordination, biocompatibility and radiation resistance that natural graphite does not have. As early as the early 1860s, Brodie discovered expanded graphite by heating natural graphite with chemical reagents such as sulfuric acid and nitric acid, but its application did not begin until a hundred years later. Since then, many countries have launched the research and development of expanded graphite, and made major scientific breakthroughs.
Expanded graphite at high temperature can instantly expand the volume of 150 to 300 times, from sheet to wormlike, so that the structure is loose, porous and curved, the surface area is enlarged, the surface energy is improved, the adsorption of flake graphite is enhanced, and the wormlike graphite can be self-mosaic, which increases its softness, resilience and plasticity.
Expandable graphite (EG) is a graphite interlayer compound obtained from natural flake graphite by chemical oxidation or electrochemical oxidation. In terms of structure, EG is a nanoscale composite material. When the EG obtained by the oxidation of ordinary H2SO4 is subjected to a high temperature above 200℃, the REDOX reaction occurs between sulfuric acid and graphite carbon atoms, producing a large amount of SO2, CO2 and water vapor, so that EG begins to expand, and reaches its maximum volume at 1 100℃, and its final volume can reach 280 times of the initial. This property allows EG to extinguish the flame by a momentary increase in size in the event of a fire.
The flame retardant mechanism of EG belongs to the flame retardant mechanism of solidification phase, which is flame retardant by delaying or interrupting the generation of combustible substances from solid substances. EG When heated to a certain extent, it will begin to expand, and the expanded graphite will become a vermicular shape with a very low density from the original scale, thus forming a good insulation layer. The expanded graphite sheet is not only the carbon source in the expanded system, but also the insulation layer, which can effectively heat insulation, delay and stop the decomposition of the polymer; At the same time, a large amount of heat is absorbed during the expansion process, which reduces the temperature of the system. In addition, during the expansion process, acid ions in the interlayer are released to promote dehydration and carbonization.
EG as a halogen-free environmental protection flame retardant, its advantages are: non-toxic, does not generate toxic and corrosive gases when heated, and produces little flue gas; The addition amount is small; No dripping; Strong environmental adaptability, no migration phenomenon; Uv stability and light stability are good; The source is sufficient and the manufacturing process is simple. Therefore, EG has been widely used in a variety of flame retardant and fireproof materials, such as fire seals, fire boards, fire retardant and anti-static coatings, fire bags, plastic fire blocking material, fire retardant ring and flame retardant plastics.
Post time: Nov-09-2023