Expandable graphite
Expandable Graphite
High-carbon, acid-intercalated natural flake graphite that exfoliates into a low-density worm structure on heating. Supplied by mesh grade and expansion rate for fire-retardant, sealing and metallurgical duty — from single bags to full truckloads.
Carbon up to 93%+
Expansion to 250 cc/g
50–270 mesh
25 kg bags · jumbo bags
What is expandable graphite?
Expandable graphite is a natural flake graphite that has been treated with an intercalant — most commonly a sulphuric-acid system — so that reactive molecules sit between the graphene layers of the crystal. The flake keeps its metallic sheen and stays chemically inert at room temperature, but the intercalant is a dormant blowing agent locked inside the lattice.
When the flake meets a rapid rise in temperature, the intercalant vaporises and forces the graphene planes apart along the c-axis. Each particle unzips into a concertina-shaped “worm” and the bulk volume grows dozens to hundreds of times, typically 100–400×. That single behaviour — a solid that turns into an insulating, non-combustible foam on demand — is what makes the material valuable across fire protection, sealing and high-temperature processing.
Because the base material is natural crystalline graphite, the expanded product still carries graphite’s core strengths: thermal and electrical conductivity, chemical resistance across most acids and alkalis, self-lubrication and stability well above 3000 °C in the absence of oxygen.
At a glance
- Silvery flake before heating; black vermicular worm after
- Onset of expansion from ~190–220 °C
- Halogen-free, low-smoke fire-retardant additive
- Odourless black powder, non-toxic in normal handling
- Not classified as hazardous for transport (IMO/IMDG)
- Grades by mesh size, carbon content and expansion rate
Standard mesh grades
Our core expandable-graphite range is specified by particle-mesh size. All four grades share a high-purity carbon base and a controlled onset temperature, so you select on flake size and expansion volume to suit your process.
| Property | 50 Mesh | 80 Mesh | 100 Mesh | 140 Mesh |
|---|---|---|---|---|
| Particle size (65% on) | 50 mesh | 80 mesh | 100 mesh | 140 mesh |
| Initial expansion temp. | 220 °C | 220 °C | 220 °C | 220 °C |
| Expansion volume @600 °C | 200 cm³/g | 200 cm³/g | 200 cm³/g | 200 cm³/g |
| Purity (carbon) | ≥93% | ≥93% | ≥93% | ≥93% |
Typical values from Rockleigh Industries lab analysis. Coarser mesh (50) gives larger worms and higher exfoliation; finer mesh (140) gives a denser, more uniform expansion — preferred for thin intumescent coatings.
Grades by carbon content & expansion rate
Where a project is driven by chemistry rather than flake size, we also stock and produce graded lots verified by batch TDS. The table below lists representative tested values across the working range.
| Grade / lot | Fixed carbon | Ash | Moisture | Expansion rate | Grain size | pH |
|---|---|---|---|---|---|---|
| High-carbon 92 | 92.37% | 7.63% | 0.60% | 250 ml/g | +100 mesh (82%) | 5.67 |
| High-carbon 91 | 91.23% | 5.9% | 0.50% | 230 ml/g | +100 mesh (70%) | 6.1 |
| Fine 30-270N | 90.36% | 9.64% | 0.87% | 38–49 cm³/g | 270 mesh (92%) | 5.4 |
| Standard 3538 | 83.86% | 16.14% | 0.95% | 56 cm³/g | −200 mesh (76%) | 6.6 |
| Economy 83 | 83.33% | 13.85% | 0.80% | 58 (@750 °C) | −200 mesh (74%) | 6.8 |
Batch-specific figures are confirmed on the Technical Data Sheet shipped with every order. Custom carbon, mesh, sulphur and expansion targets available on request.
Applications
Packaging & supply
Standard packing is 25 kg paper bags (or 50 lb bags) palletised inside 1 MT jumbo bags; custom packing is available to order. Material is shipped from stock where possible or produced to specification. Store in the original, unopened package in a clean, cool, dry place — the product may cake if left open to moisture.
Technical documents
Download the datasheets for full tested values by grade. Each TDS is issued per production batch.
PDFTDS — Carbon 92% / ER 250High-carbon high-expansion grade
PDFTDS — Carbon 91% / ER 230High-carbon grade
PDFTDS — Grade 30-270N (fine)270-mesh fine grade
PDFTDS — Grade 3538Standard −200 mesh grade
PDFTDS — Carbon 83% / ER 58Economy grade
SDSSafety Data SheetCAS 7782-42-5 · handling & transport
Frequently asked questions
What temperature does expandable graphite start to expand at?
Onset depends on the intercalation system. Our standard mesh grades begin expanding around 220 °C, while high-carbon lots can start as low as 190–200 °C. Full worm formation develops as the temperature climbs toward 600 °C and above.
How much does it expand?
Bulk volume typically grows 100–400 times. Measured expansion volume runs from roughly 38 cm³/g on fine grades up to 250 cm³/g on high-expansion high-carbon lots.
Is it hazardous to ship or handle?
No. Expandable graphite is an odourless black powder that is not considered toxic in normal handling and is not classified as hazardous for transport under IMO/IMDG. Minimise dust and store dry. See the SDS for full detail.
Which grade should I choose?
Fire-retardant coatings usually favour finer mesh (100–140) for a smooth film; sealing and gasket foil favour higher carbon and larger expansion; metallurgical cover uses coarser, lower-cost grades. Send us your target expansion rate, carbon and mesh and we will match a grade.
What are the minimum order quantities?
We supply from single 25 kg bags for trials through to full jumbo-bag pallet loads and truckload volumes. Contact us for current stock and lead time.
Request a quote or a sample
Tell us your grade, mesh and volume — we will confirm price, availability and lead time, and send the matching batch TDS.
From Stock or Special Order - Any grade / Any Packaging.
If you are unable to locate a Chemical or Mineral you need, our sales department can custom source any needed materials for you directly.
