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As a leading Expanded Graphite supplier, we deliver high-quality products across diverse grades to meet evolving needs, empowering global customers with safe, efficient, and compliant chemical solutions.
How to control the expansion multiple when preparing Expanded Graphite?
This material is made of natural flake graphite (carbon content 99%, particle size 50 mesh) as raw material, immersed in a mixture of concentrated sulfuric acid and nitric acid (volume ratio 3:1), solid-liquid ratio 1:5, and reacted at room temperature for 2 hours, like pickled meat, so that acid groups are embedded between graphite layers. Wash with water to a pH value of 5-6, centrifugal dehydration, and dry at 80℃ to obtain expandable graphite. Place it in a muffle furnace and heat it instantly at 300℃ for 30 seconds. The gas between the graphite layers expands to obtain Expanded Graphite. The expansion multiple needs to be controlled at 200-300mL/g, like popcorn with a certain degree of puffiness. If it is too high, it will be fragile, and if it is too low, the flame retardancy will be poor. After expansion, it is screened and 50-200 mesh particles are selected, with ash content <1% and fixed carbon >98%, which are excellent products for sealing and flame retardancy.
What is the application of Expanded Graphite in sealing materials?
This product is added to nitrile rubber at a dosage of 30%, mixed with carbon black and vulcanizer, and rolled into a sealing gasket with a Shore hardness of 70A and a compression rebound rate of >45%, which meets the GB/T 19228.3 standard. At a high temperature of 200°C, the gasket still maintains good elasticity, and the leakage rate is <1×10⁻⁶Pa・m³/s, which is much lower than the 1×10⁻⁴ of asbestos gaskets. It is used for flange sealing and can withstand 1000 hours of immersion in kerosene and engine oil, with a volume change rate of <5%. Therefore, it is widely used in petrochemical pipelines and automobile engine seals. It can prevent medium leakage and has high temperature resistance. It is an environmentally friendly material that replaces asbestos.
What is unique about the flame retardant mechanism of Expanded Graphite?
This material does not burn when exposed to fire, and its volume is stable at high temperatures. Its porous structure absorbs heat like a sponge, making it difficult for the substrate temperature to rise to the ignition point. In polymers, expanded graphite flakes can block oxygen from contacting combustibles, such as building walls to block fires, while inhibiting molten dripping. When compounded with APP for polyethylene, a "graphite-carbon layer" composite barrier is formed during combustion, and the oxygen index is increased to 35%, 8 percentage points higher than when APP is used alone. Its flame retardancy is a physical effect, does not produce toxic gases, and the smoke density level is reduced by 40%, so it is suitable for flame retardant materials in crowded places such as subways and hospitals, taking into account safety and environmental protection.
What is the difference between the performance of Expanded Graphite and ordinary graphite?
Compared with ordinary graphite, Expanded Graphite has a specific surface area 100 times larger, reaching 50m²/g, and has a stronger adsorption capacity. The adsorption of organic vapor can reach 80% of its own weight. In terms of mechanical properties, its compression strength reaches 0.5MPa and the rebound rate is 45%, while ordinary graphite is brittle and inelastic. In terms of flame retardant efficiency, adding 5% can make polypropylene reach UL94 V-1 level, while ordinary graphite requires 15% because the barrier effect of the expanded sheet is more significant. Although the cost is 5 times higher than that of ordinary graphite, its multifunctionality (sealing, flame retardant, adsorption) makes it more cost-effective and suitable for high-end fields.
What are the specifications for processing and storage of Expanded Graphite?
This product is packaged in kraft paper bags, 20kg per bag, lined with PE film to prevent moisture absorption, and covered with woven bags after the bag mouth is tied tightly. Store in a dry warehouse with a relative humidity of less than 60%, avoid mixing with oxidants and strong acids, and stay away from fire sources, because it is easy to raise dust when drying, but it does not self-ignite. Wear a dust mask during processing, install a dust removal system in the workshop, and the dust concentration is less than 8mg/m³. When mixed with rubber, it must be plasticized in an open mill first, and then gradually added. The temperature must be controlled below 80℃ to prevent rubber aging. If the material clumps after long-term storage, it can be loosened by manual kneading without affecting the performance, ensuring it can be used at any time.