How Is Flexible Graphite Made?
Graphite gasket material is well known by industries for use in various applications. Though it is considered a non-metallic material, it is electrically and thermally conductive as a metal alloy. Flexible graphite is 95% to 99% carbon and is made from exfoliated compressed graphite particles. Since it is inert to many harsh chemicals and is heat resistant up to several thousand degrees, it is used in applications and industries like oil and gas, food processing, automotive and aerospace as seals and gaskets for use in flanges, pumps, and heat exchangers as examples. If you’re in the industry or business of manufacturing raw materials or various composites, you do understand what it takes and the science that is applied. For the rest of us, it is good to get a sense of why materials may take extended lead time in production or know the challenging factors facing suppliers. The method of producing flexible graphite involves more than just compression of particles and manufactures do have deviations to their process from others. The following is a general overview of the manufacturing process:
- Purification and Flaking: Natural graphite ore is purified to remove impurities. A mechanical process creates thin flakes which increases the surface area,
- Chemical Treatment: The now purified flakes are treated with a strong oxidizing agent, typically an acidic solution. This process creates intercalation compounds. Intercalation refers to the process of inserting atoms, molecules, or ions (called guests) between the layers (called host layers) of a layered material. This creates a layered sandwich material by introducing functional groups that increase the space between the graphite layers.
- Expansion: Through a heating process the graphite undergoes a rapid expansion. This rapid temperature increase forces the layers apart, significantly increasing the volume of the material.
- Shaping and Compacting: Methods such as pressing allow the expanded structure of flakes to interlock. The graphite flakes when compressed form the desired final shape, such as sheets, rolls, or gaskets.
Note:
- Some manufacturers may utilize various particle sizes of expanded graphite during compaction to achieve specific properties in the final product.
- The exact details of the process can be proprietary and vary depending on the manufacturer.
Once in hand with precision components manufacturers, custom graphite gaskets and seals are made by several methods including laser cutting, die-cutting, digital knife cutting, CNC machining and waterjet cutting. Graphite gasket material is processed by these manufacturing techniques and supports an array of applications as mentioned above and for heat management for HVAC systems, for electrical conductivity in high temperature environments like heating electrodes in vacuum furnaces and for insulation of furnaces, kilns, and industrial ovens.
Graphite gaskets, seals and rings and other components are not typically off-the-shelf products that can be manufactured easily. Modern material was developed around the 1960’s which took raw form of mineral ore and by a chemical and mechanical processing turn into flexible graphite we have come to know. With technological advancements in processing, this versatile material has kept pace to support the needs of industrial growth and looks to be a part of industry for many years to come.
What Are the Applications of Flexible Graphite?
Graphite is the solid form of carbon and as a solid it is used as a lubricant, in pencils, and for electrodes and other applications. What graphite is better known for are industrial applications as a first line of defense as a gasket and seal. It keeps the lines of systems intact by holding back scorching temperatures, corrosive chemicals and relentless pressure. It provides this stability in the form of flexible graphite. This unique structured material is produced using natural flake graphite that is immersed into a chromic acid bath. It is followed by concentrated sulfuric or nucleic acid. This forces the crystal lattice planes apart and expands the graphite, creating a greater surface area. Its impact goes beyond mere sealing; it’s the unsung conductor in the symphony of industrial progress, ensuring the smooth operation of countless machines and processes for numerous industries. Known for its machineability and holding tight tolerances it also has exceptional thermal conductivity, heat resistance, and chemical resistance, flexible graphite is often used in:
- Fugitive emissions applications: Preventing gases and vapors from escaping from pipelines, storage tanks and other equipment.
- Nuclear seals: For use in sealing systems used in nuclear energy and research.
- Power generation: In addition to using flexible graphite for flanges, valves, and heat exchangers, the power generating industry uses it on steam traps and condensate lines to prevent steam from escaping.
- Thermal pads: Conducting heat away from heat-generating components. Conformability fills gaps and gives good thermal contact.
- Oil and gas and chemical plants: Used primarily to provide seals for flanges, valves, and pumps.
- Oven seals: Improving heat management for door gaskets, oven panels and expansion joints.
- Semiconductors: Used various stages of semiconductor manufacturing to manage heat as susceptors by creating uniform heat distribution. For heater elements used in processing and for heat sinks.
- Pipe flange gaskets: For high pressure, high temperature, and corrosive environments. Flexible graphite gasket materials are the preferred choice.
- Valve stem seals: Flexible graphite gaskets are used in valve stems for their low friction, low maintenance, chemical compatibility and for temperature resistance.
- Aerospace engine and propulsion seals: Prevents high pressure gases and fluids from leaking exhaust seals and turbomachinery seals. Reliability, safety, low weight and performance are all critical factors that the industry relies upon by using flexible graphite gaskets.
Graphite gasket material is used in many applications for its ability to provide safeguards for various flow systems and containers by preventing gases and heat from escaping. Its resilient characteristics have been proven over many years of use, the superior performance in thermal management and chemical resistance. Without these capabilities, private industry and the public would not be safe during manufacturing and processing of the systems that we rely on for energy, petroleum products, consumer products and aerospace integrity, to name a few. Custom graphite gaskets manufactured to high quality standards by methods such as laser cutting, CNC machining, waterjet cutting, and die-cutting provide precision components out of this remarkable material for both volume manufacturing and R&D/protype support. With new technologies and the ever-growing needs for more industry, Flexible graphite will be a key element in future industrial applications.