Expandable Graphite: High-Performance Carbon Material for Flame Retardancy & Sealing

High expansion ratio.
Excellent electrical conductivity.
High carbon content with low impurity

Expandable graphite and worm-like graphite after expansion are placed together.

Description

Expandable graphite, also known as graphite acid, acidized graphite or graphite oxide, is a graphite interlayer compound prepared by using chemical oxidation (chemical method), electrochemical method, microwave method, explosion method and gas phase volatilization method for natural flake graphite treatment. After special treatment, expandable graphite can be instantly expanded into worm-like shape under high temperature.

Different types of insert lead to different intercalation structures, giving it unique physical and chemical properties such as high electrical and thermal conductivity, superconductivity, magnetic permeability, battery performance, catalytic properties, and expansion performance. The application of expandable graphite covers the practical use in high-conductivity materials, battery materials, efficient catalysts, hydrogen storage materials, and improvements in expansible graphite sealing materials.

Features

High expansion ratio. The volume can expand by several hundred to several thousand times at elevated temperatures. The expansion rate varies depending on the original flake size and the chemical reagents employed.
Outstanding electrical conductivity. It retains the electrical conductivity of natural graphite, making it suitable for energy storage and conductive material applications.
Controllable initial expansion temperature. The initial expansion temperature can be adjusted as required, typically ranging from 160 °C to 300 °C, to accommodate various flame retardancy or heat treatment processes.
Environmentally friendly and safe. Free from halogens, heavy metals, and other hazardous substances; it generates low smoke and low toxicity during combustion, in compliance with green flame retardancy standards.
High purity and stable performance. Based on high-purity natural flake graphite as the raw material, it features high carbon content, low impurity, and excellent product quality consistency.
Easy to process. It is suitable for the production of flexible graphite products such as graphite paper, sealing gaskets, and packing materials.

Specifications

According to the sulphur content after expansion, expandable graphite is divided into sulfurous expandable graphite (≥ 0.120%) and low sulfur expandable graphite (< 0.120%). The specific properties of expandable graphite is shown in the table below.

Table 1: Expandable Graphite Technical Indicators
Category	Before Expansion				After Expansion
Category	Moisture	pH Value	Weight of Screen Residue (150 μm, 180 μm, 300 μm）	Expansion Volume (mL/g)	Sulfur Content	Fixed Carbon Content
Sulfurous expansible graphite	< 1.00%	3.00–9.00	≤ 20.00%	50–400	≥ 0.120%	90% –99%
Low sulfur expandable graphite	< 1.00%	3.00–9.00	≤ 20.00%	50–400	< 0.120%	90% –99%
Notes: These properties are typical values and not guaranteed.

Applications

Expandable graphite is widely used in flame retardancy, fire protection, and sealing applications. At elevated temperatures, it rapidly expands to form a thermal insulation barrier, making it an ideal halogen-free flame retardant for use in PU foams, engineering plastics, fireproof sealing components, and fire-resistant building materials. It is also a key raw material for the production of flexible graphite sheets, gaskets, and thermally conductive sealing materials, serving applications in thermal conductivity and sealing.

The role of expandable graphite in flame retardant coatings