Carbon fiber products are widely distributed in our lives. Carbon fiber is a good material for making many daily necessities. So, what is carbon fiber, what are the characteristics of carbon fiber, and what are the advantages of carbon fiber compared with other ordinary materials. In fact, there are many types of carbon fiber. So, what are the classifications of carbon fiber, and what are the advantages and characteristics of different classifications? Now I will introduce them to you one by one, hoping to help everyone understand carbon fiber.
What is carbon fiber?
Carbon fiber (CF) is a high-strength, high-modulus fiber with a carbon content of more than 95% New fiber materials with high fiber content. It is a microcrystalline graphite material obtained by stacking organic fibers such as flake graphite microcrystals along the axial direction of the fiber and undergoing carbonization and graphitization treatments. Carbon fiber is "flexible on the outside and rigid on the inside". It is lighter than metallic aluminum, but stronger than steel. It is corrosion-resistant and has high modulus. It is an important material in national defense and civilian applications. It not only has the inherent characteristics of carbon materials, but also has the soft processability of textile fibers. It is a new generation of reinforcing fiber.
Carbon fiber has many excellent properties. Carbon fiber has high axial strength and modulus, low density, high specific performance, no creep, ultra-high temperature resistance in non-oxidizing environment, good fatigue resistance, specific heat and The electrical conductivity is between non-metals and metals, the thermal expansion coefficient is small and anisotropic, the corrosion resistance is good, and the X-ray transmittance is good. Good electrical and thermal conductivity, good electromagnetic shielding, etc.
Compared with traditional glass fiber, the Young's modulus of carbon fiber is more than 3 times; compared with Kevlar fiber, the Young's modulus is about 2 times, and it is resistant to organic solvents and acids. , does not dissolve or swell in alkali, and has outstanding corrosion resistance.
What are the classifications of carbon fiber?
According to the source of raw materials, carbon fiber can be divided into polyacrylonitrile-based carbon fiber, tube pitch-based carbon fiber made of 1K carbon fiber, viscose-based carbon fiber, phenolic-based carbon fiber, Vapor-phase grown carbon fiber; according to performance, it can be divided into general type, high strength type, medium mold high strength type, high mold and ultra high mold carbon fiber; according to the state, it can be divided into filament, short fiber and chopped fiber.
According to mechanical properties, it is divided into general type and high performance type. The strength of general-purpose 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 250GPa) and high model (modulus 300GPa or above). Those with a strength greater than 4000 MPa are also called ultra-high strength models; those with a modulus greater than 450 GPa are called ultra-high models.
With the development of the aerospace and aviation industry, high-strength and high-elongation carbon fibers have also appeared, with an elongation greater than 2. The largest amount of polyacrylonitrile PAN-based carbon fiber is used.
More than 90% of the carbon fibers on the market are mainly PAN-based carbon fibers.
Since the mystery of carbon fiber has not yet been completely unveiled, people cannot directly use carbon or graphite to make it. They can only use some carbon-containing organic fibers (such as nylon yarn, acrylic yarn, rayon, etc.) As raw materials, carbon fibers are produced by combining organic fibers with plastic resins and carbonizing them.
PAN-based carbon fiber
The production process of PAN-based carbon fiber mainly includes two processes: raw fiber production and raw fiber carbonization: first, it is processed through a series of processes such as acrylonitrile polymerization and spinning. The polyacrylonitrile fiber or raw filament, called the "mother", is put into an oxidation furnace for oxidation at 200 to 300°C, and carbonized in a carbonization furnace at a temperature of 1000 to 2000°C. and other processes to make carbon fiber.
Pitch-based carbon fiber
The United States invented the mesophase pitch containing base metal for textile pitch-based carbon fiber. After the raw silk is stabilized and carbonized, the tensile strength of the carbon fiber is 3.5G. Pa, the modulus is 252G Pa; France has developed heat-resistant and highly conductive mesophase pitch-based carbon fiber; Poland has developed a new method of metal-coated carbon fiber. For example, copper-coated pitch-based carbon fiber is made by a mixing method, first using The copper salt is mixed with isotropic coal pitch, centrifugally spun, stabilized in air and treated in high-temperature hydrogen to obtain copper alloy carbon fiber. ?The production capacity of pitch-based carbon fiber in the world is small. The research and development of domestic pitch-based carbon fiber was earlier, but there is a large gap compared with foreign countries in terms of development, production and application. [18-19]
Carbon fiber is divided into aerospace grade and industrial grade according to different product specifications, also known as small tows and large tows. Carbon fibers above 48K are usually called large-tow carbon fibers, including 360K and 480K. Aerospace-grade carbon fiber was mainly 3K at the beginning, and gradually developed into 12K and 24K. It is mainly used in national defense industry and high technology, as well as sports and leisure products, such as aircraft, missiles, rockets, satellites, fishing rods, clubs and rackets, etc. Industrial-grade carbon fiber is used in different civil industries, including: textiles, medicine and health, mechanical and electrical, civil construction, transportation and energy, etc.
Above, the editor introduced to you in detail what carbon fiber is, and compared carbon fiber with ordinary materials, so that everyone can have a clearer understanding of the characteristics of carbon fiber materials and the advantages of carbon fiber. These are There's a big reason why it's widely used. The editor also introduced several different types of carbon fiber and their corresponding characteristics. Carbon fiber products are widely used in our daily lives. Its products are still worth buying by consumers. I hope the editor’s introduction can help. to everyone.