Expandable Graphite (Expandable Graphite Flake) CAS 7782-42-5

Introduction to Expandable Graphite Flake

Expandable Graphite Flake is manufactured via chemical intercalation of natural crystalline flake graphite. Oxidizing intercalants, typically sulfuric acid-based complexes, are inserted between graphene layers. When heated above activation temperature, the intercalant vaporizes and separates graphite layers along the c-axis, turning dense flakes into porous, low-density graphite worm structures.

The material offers strong thermal stability, chemical inertness and intumescent char-forming performance. Expansion onset temperature, expansion volume and flake mesh size can be tuned to match specific processing conditions and end-use requirements. The exfoliated structure retains high electrical and thermal conductivity across the interconnected carbon network.

Chemical & Physical Properties of Expandable Graphite

Applications of Expandable Graphite

Building Fire Safety Systems
Deployed in intumescent firestop seals, door gaskets, cable transit blocks and pipe penetration systems. The material expands rapidly on fire exposure to fill gaps and voids, restricting flame spread, smoke migration and toxic gas transfer between building compartments.

Flame-Retardant Polymers & Coatings
Integrated into polyurethane foams, polyolefin compounds and epoxy resin systems. It works as a char-forming synergist with phosphorus-based flame retardants, creating a rigid carbon layer that shields base polymer from radiant heat and limits oxygen supply to the combustion zone.

Refractory & Metallurgical Materials
Used as a functional carbon additive in magnesia-carbon bricks, ladle linings and continuous casting mold powders. Volumetric expansion during sintering compensates for thermal shrinkage of refractory matrices, improving structural integrity and thermal shock resistance of high-temperature linings.

Flexible Graphite & EMI Components
Processed through continuous furnace expansion to produce exfoliated graphite, which is calendered into thin flexible graphite sheets. These sheets serve as high-temperature gaskets, thermal interface materials and EMI shielding components for power, electronics and aerospace applications.

Storage & Safety Precautions for Expandable Graphite

• Store in original sealed woven bags or jumbo bags in a cool, dry warehouse below 30 °C. Protect from direct sunlight, high humidity and strong oxidizing agents. Moisture ingress degrades intercalant performance and reduces final expansion volume. Shelf life reaches 24 months under proper conditions.
• Wear N95 dust masks and safety goggles during bulk handling and dry blending operations. Fine graphite dust may cause mechanical irritation to eyes and respiratory tracts. Install local exhaust ventilation in processing areas to keep airborne dust within occupational exposure limits.
• Transport in waterproofed dry cargo containers. The material is classified as non-dangerous under IATA/IMDG/ADR regulations. Verify expansion volume and fixed carbon content upon receipt via standard 900 °C crucible test.

Expandable Graphite FAQ

Q: How does Expandable Graphite work as a polymer flame retardant?

A: Heat expands graphite via intercalant vaporization. It forms an insulating carbon char layer that blocks heat and oxygen, suppressing flame spread without toxic fumes.

Q: Can Expandable Graphite onset match polymer processing temperatures?

A: Yes. By adjusting intercalation chemistry, grades activate from 150 °C for polyolefins to over 300 °C for engineering resins, preventing premature expansion during processing.

Q: What reduces Expandable Graphite expansion during storage?

A: Moisture absorption or warm ambient exposure causes intercalant off-gassing. Store in sealed moisture-proof bags below 30 °C. Test in a pre-heated 900 °C furnace for accurate expansion results.