How is Carbon Fiber Made?

 

Carbon Fiber is a fibrous carbon material. It is a new type of material with greater strength than steel, lower density than aluminum, more corrosion-resistant than stainless steel, more high-temperature resistant than heat-resistant steel, and conductive like copper, and has many valuable electrical, thermal and mechanical properties.

 

Aircraft made of composite materials made of carbon fiber and plastic are not only light, but also consume less power, have high thrust and low noise; using carbon fiber to make computer disks can increase the computer’s storage capacity and computing speed; using carbon fiber reinforced plastic to make satellites and rockets and other spacecraft has high mechanical strength and small mass, which can save a lot of fuel.

 

At present, people cannot directly use carbon or graphite to extract carbon fiber. They can only use some carbon-containing organic fibers (such as nylon, acrylic, rayon, etc.) as raw materials, combine organic fibers with plastic resins, place them in a rare gas atmosphere, and heat carbonize them under a certain pressure. Carbon fiber is a fibrous carbon material with a carbon content of more than 90% in its chemical composition.

 

Since carbon cannot be melted at high temperatures (sublimates above 3800K) and is insoluble in various solvents, it is not possible to use carbon to make carbon fibers. Carbon fibers can be made by solid-phase carbonization of high-molecular organic fibers or gas-phase pyrolysis of low-molecular hydrocarbons. Most of the carbon fibers produced and sold in the world are made by solid-phase carbonization of polyacrylonitrile fibers.

 

The Steps of its Production are

 

A Pre-oxidation: heating in air, maintaining at 200-300 degrees for tens to hundreds of minutes. The purpose of pre-oxidation is to convert the linear molecular chain of polyacrylonitrile into a heat-resistant ladder structure so that it will not melt or burn during high-temperature carbonization and maintain the fiber state.

 

B Carbonization: heating to 1200-1600 degrees in an inert atmosphere, maintaining for several minutes to tens of minutes, can produce product carbon fibers; the inert gas used can be high-purity nitrogen, argon or helium, but generally high-purity nitrogen is used.

 

C Graphitization: Then heat to 2000-3000 degrees in an inert atmosphere (generally high-purity argon) for several seconds to tens of seconds; the carbon fiber generated in this way is also called graphite fiber. Carbon fiber has excellent fineness (one of the ways to express fineness is the number of grams of 9000 meters of fiber), generally only about 19 grams; the tensile force is as high as 300KG/MM2; it also has a series of excellent properties such as high temperature resistance, corrosion resistance, electrical conductivity, heat transfer, and small expansion coefficient.

 

At present, there are almost no other materials that have as many excellent properties as carbon fiber. At present, carbon fiber is mainly made into carbon fiber reinforced plastic for application. This reinforced plastic is superior to steel and fiberglass, and has a wide range of uses, such as manufacturing important materials such as rockets and spacecrafts; manufacturing jet engines; manufacturing corrosion-resistant chemical equipment, etc. Badminton: Most badminton rackets are now made of carbon fiber.

 

Carbon Fiber Inorganic polymer fiber with a carbon content of more than 90%. Among them, the carbon content of more than 99% is called graphite fiber. Carbon fiber has high axial strength and modulus, no creep, good fatigue resistance, specific heat and conductivity between non-metal and metal, small thermal expansion coefficient, good corrosion resistance, low fiber density, and good X-ray transmittance.

 

However, its impact resistance is poor, it is easy to be damaged, it oxidizes under the action of strong acid, and metal carbonization, carburization and electrochemical corrosion will occur when it is compounded with metal. Therefore, carbon fiber must be surface treated before use. Carbon fiber can be made of polyacrylonitrile fiber, asphalt fiber, viscose fiber or phenolic fiber by carbonization; it can be divided into filament, short fiber and short fiber according to the state; it can be divided into general type and high performance type according to mechanical properties.

 

The strength of general carbon fiber is 1000 MPa and the modulus is about 100 GPa. High-performance carbon fiber is divided into high-strength type (strength 2000 MPa, modulus 250 GPa) and high model (modulus above 300 GPa). The strength greater than 4000MPa is also called ultra-high strength type; the modulus greater than 450GPa is called ultra-high model.

 

With the development of aerospace and aviation industries, high-strength and high-elongation carbon fibers have also appeared, with an elongation greater than 2%. The largest amount is polyacrylonitrile-based carbon fiber. Carbon fiber can be processed into fabrics, felts, mats, belts, paper and other materials. In addition to being used as thermal insulation materials, carbon fiber is generally not used alone. It is mostly added as a reinforcing material to resins, metals, ceramics, concrete and other materials to form composite materials.

 

Carbon Fiber reinforced composite materials can be used as aircraft structural materials, electromagnetic shielding and static removal materials, artificial ligaments and other body substitute materials, as well as for the manufacture of rocket shells, motor boats, industrial robots, automobile leaf springs and drive shafts. Carbon fiber is a fiber with a carbon content of more than 90% made from polyacrylonitrile fiber, asphalt fiber or viscose fiber through oxidation, carbonization and other processes.