European consultant ProGraphite has started research on producing expandable graphite using materials from the Woxna graphite mine, which Canadian firm Leading Edge Materials owns in Sweden.

Leading Edge has previously produced expandable and expanded graphite products using Woxna graphite as a feedstock.

Expandable graphite is a potential value-add product for larger flake natural graphite from Woxna that will not go to the lithium-ion battery anode markets. Leading Edge says demand for expandable graphite for fire resistant building products and textiles are substantial and fast growing, while emerging markets exist as a precursor for graphene manufacturing.

The company explains that expandable graphite is manufactured by treating crystalline graphite with mild non-toxic chemicals that position between individual graphite flakes. When exposed to heat, the chemical converts from a solid or liquid to a gas phase causing an accordion-like expansion of the graphite, which becomes 200 times to 400 times its previous volume. 

When used as a fire retardant in building materials, the expandable graphite is incorporated to form a surface barrier layer in the event of a fire. 

“Expandable graphite provides potential high-value applications for graphite with larger flakes and at a lower purity than that required for battery anode materials.  We are now working with a highly experienced European research group to ensure optimal materials can be produced for building product and graphene supply chains. This work runs in parallel with our ongoing work for battery anode materials and provides potential for a deeper product network,” Leading Edge interim CEO Mark Saxon states.

Samples of graphite from the Woxna mine have been delivered to ProGraphite laboratory for characterisation and testing. Graphite for graphene and expandable graphite is typically of a coarser flake size (greater than about 100 micron) than that required for lithium-ion battery anode manufacture (typically 30 micron to 100 micron). A range of test conditions and intercalation chemicals are being applied to develop products suitable for various end markets.