Also known as "intumescent flake graphite," expandable graphite is a synthesized intercalation compound of graphite that expands or exfoliates when heated. This material is manufactured by treating flake graphite with various intercalation reagents that migrate between the graphene layers in a graphite crystal and remain as stable species.
If exposed to a rapid increase in temperature, these intercalation compounds decompose into gaseous products, which results in high inter-graphene layer pressure. This pressure develops enough force to push apart graphite basal planes in the "c" axis direction. The result is an increase in the volume of the graphite of up to 300 times, a lowering of bulk density, and approximately a 10-fold increase in surface area.
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