In the realm of high-temperature applications, flexible graphite has emerged as a versatile and reliable material, offering exceptional thermal conductivity, chemical resistance, and sealing properties. In this technical blog, we delve into flexible graphite's unique characteristics and diverse applications in challenging high-temperature environments.
Understanding Flexible Graphite
Flexible graphite is a form of carbon derived from natural graphite flakes that have been expanded and processed into a highly flexible and resilient material. Through an intercalation process, graphite flakes are treated with chemical agents, which expands the flakes before they are compressed into sheets or rolls. This process gives it unique properties that are quite different from those of its original form.
Having the capability to handle a pH range of 0 to 14, flexible graphite provides exceptional chemical resistance. However, what truly distinguishes flexible graphite is its remarkable temperature range. Flexible graphite can withstand temperatures ranging from -400°F to 850°F in an oxygen environment. For steam applications, the temperature range increases to 1,200°F. In environments without oxygen, flexible graphite can withstand temperatures ranging from an astonishing -400°F to 5,400°F.
Key Properties of Flexible Graphite
- High-Thermal Conductivity: Flexible graphite exhibits outstanding thermal conductivity, allowing for efficient heat transfer and distribution in high-temperature environments. This property makes it an ideal choice for thermal management applications, including heat exchangers, gaskets, and insulation.
- Chemical Inertness: Flexible graphite is chemically inert and resistant to most corrosive chemicals, acids, and solvents. This resistance enables its use in harsh chemical processing environments, where conventional materials may degrade or fail.
- Low Permeability: Flexible graphite possesses low gas and liquid permeability, making it an effective sealing material for high-pressure and high-temperature applications. Its ability to maintain a tight seal under extreme conditions enhances equipment reliability and prevents leakage in critical systems.
- Mechanical Flexibility: Despite its high thermal conductivity and chemical resistance, flexible graphite remains flexible and conformable, allowing it to adapt to irregular surfaces and intricate geometries. This flexibility ensures optimal contact and sealing performance in various sealing applications.
- Resiliency and Recovery: Flexible graphite is a unique gasket material that maintains its characteristics across a wide range of temperatures. Unlike polymer-based or polymer-filled gasket materials, it does not soften at elevated temperatures or harden at low temperatures. This stability allows it to withstand millions of compression cycles while maintaining a recovery rate of 10-15%, regardless of temperature fluctuations. This combination of durability and resilience makes flexible graphite an excellent choice for seals that are subjected to thermal or mechanical cycling.
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Applications of Flexible Graphite in High-Temperature Environments
- Die-formed rings, Braided Packing, Gaskets, and Seals: Flexible graphite gaskets, seals, and die-formed rings are widely used in industrial applications, including petrochemical, power, automotive, and aerospace industries, where they provide reliable sealing solutions for flanges, valves, pumps, and heat exchangers operating at elevated temperatures and pressures by dissipates frictional heat away from the shaft, enabling high shaft speeds and reducing leakage.
- Heat Exchangers: Flexible graphite heat exchangers offer efficient heat transfer and corrosion resistance in chemical processing, power generation, and HVAC systems. Their ability to withstand high temperatures and thermal cycling makes them well-suited for demanding thermal management applications.
- Insulation: Flexible graphite materials and insulation products are employed in furnaces, kilns, expansion joints, mixers, agitators, and industrial ovens to minimize heat loss, improve energy efficiency, and maintain temperature uniformity. Their thermal stability and insulating properties contribute to enhanced process performance and reduced operating costs.
- Thermal Management and Electrical Components: Flexible graphite is used as a heat spreader and thermal interface material in electronic devices, such as power modules, LEDs, and battery packs, where efficient heat dissipation is critical for device reliability and longevity. Compared to conventional heating elements, like Cal rods and metal foil heaters, today's revolutionary thermal management solutions utilize innovative PTC (Positive Temperature Coefficient), NTC (Negative Temperature Coefficient), and thermal energy storage (TES) technology.
- Nuclear Applications: Flexible graphite is the go-to sealing material for nuclear applications. Its appeal lies in its exceptional resistance to high temperatures, chemical inertness, long-term durability, and fire resistance. However, its most critical advantage is its ability to withstand the effects of radiation without significant degradation, maintaining its sealing capabilities and mechanical properties. Additionally, flexible graphite has low outgassing characteristics, which reduces the risk of contamination in sensitive nuclear environments. This is crucial because many other sealing materials, including fluoropolymers, tend to degrade, outgas, create reactive byproducts, and pose fire and toxicity risks when exposed to radiation. These factors make flexible graphite an exceptionally reliable choice for nuclear designs.
Conclusion
The utilization of flexible graphite presents an exceptional material solution for high-temperature applications due to its distinct blend of thermal conductivity, chemical resistance, fire resistance, and sealing performance. The versatility and reliability of this technology make it an essential tool in multiple industries. It plays a critical role in maintaining equipment reliability, improving process efficiency, and ensuring safety even under extreme operating conditions. Flexible graphite is a leading material in high-temperature applications, thanks to its ability to meet the increasing demand for high-performance materials driven by technological advancements.
Wrap-Up
To learn more about flexible graphite and how this versatile material can solve your most critical challenge, contact the team at CDI to learn more. Contact the application engineers and materials scientists here to see how we can support your high-temperature challenges with flexible graphite.
EGC, which had for years procured flexible graphite materials from alternative suppliers, understood that stricter control was required to guarantee the product's consistency in density, thickness, and purity. 1985 saw the introduction of an EGC-created brand that would significantly transform the material's grading. To learn more about EGC's coveted brand of Thermafoil® Flexible Graphite, contact a CDI or EGC representative today. Visit EGC