Overview
High purity expandable graphite is produced through chemical treatment of natural flake graphite with intercalating agents like sulfuric acid. When heated rapidly, the intercalated compounds decompose, causing the graphite layers to separate and expand dramatically. This unique property makes it invaluable for industrial applications requiring thermal resistance or sealing capabilities. The material typically exceeds 99% carbon purity, with minimal ash content. Its performance depends on factors like particle size distribution and expansion ratio, which can be tailored during manufacturing. Unlike conventional graphite, its expanded form creates a vermicular structure with high surface area and flexibility.
Physical and Chemical Properties
The unexpanded material appears as metallic gray flakes with a layered hexagonal crystal structure. Upon heating above 200-300°C, it expands perpendicular to the basal planes, forming low-density worms with excellent compressibility. Expanded graphite maintains conductivity while becoming highly absorbent to oils and viscous materials. Chemically, it resists corrosion from most acids (except strong oxidizers) and alkalis up to 500°C. The expansion process increases its thermal stability in air compared to untreated graphite, with oxidation resistance up to 450°C. Its thermal conductivity ranges between 5-150 W/m·K depending on compression.
Main Applications
In fire protection, expanded graphite forms intumescent seals and coatings that swell to block flames and heat transfer. It's used in building materials, cable insulation, and aerospace components. The automotive industry employs it for high-temperature gaskets and battery thermal management systems. Other uses include flexible graphite foils for electronics cooling, lubricant additives, and conductive fillers in polymers. Recent developments focus on energy storage, where its porous structure benefits lithium-ion battery anodes and hydrogen storage systems.
Safety and Storage
While generally safe, the fine powder requires dust control measures during handling to prevent respiratory irritation. Storage areas should be well-ventilated and separated from strong oxidizers like chlorates or nitrates, which could react with residual intercalants. Expanded material is non-flammable but may smolder in direct flame contact. Spills should be collected dry—avoid water washing as it could spread particles. Personal protective equipment (PPE) including N95 masks and safety goggles is recommended for bulk processing.
B2B Procurement Guide
Key specifications to evaluate include: expansion volume (typically 100-300 ml/g), sulfur content (<2% for corrosion-sensitive uses), and particle size (50-500µm common). Verify purity through ash content testing (<1% for high-end applications). Suppliers may offer pre-expanded or ready-to-expand forms. Consider logistics: unexpanded graphite ships more economically but requires on-site expansion equipment. Request samples to test compatibility with your processing methods, especially for composite materials.
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