Carbon felts are divided into three series, namely, polyacrylonitrile-based (PAN) carbon felts, rayon-based carbon felts, and pitch-based carbon felts. The two most commonly used are polyacrylonitrile (PAN)-based carbon felts and rayon-based carbon felts. So what is the difference between polyacrylonitrile (PAN)-based carbon felts and rayon-based carbon felts?
Differences in production processes
PAN-based carbon felt processing technology
- Polymerization: The purified material is reacted to prepare spinning liquid. After the polymerization is finished, it will be desingled and defoamed.
- Spinning: After spraying from the spinneret, the filaments will go through the steps of solidifying bath, washing, hot water stretching, up stretching, steam drawing, heat setting, etc., and finally become PAN filaments.
- Needling: PAN raw silk is needled to produce felt.
- Pre-oxidation, carbonization: Make sure the felt become into carbon fiber materials with carbon content morethan 90%. At present, the industrial production operation generally pre-oxidizes the PAN raw fiber through an air oxidation furnace with a temperature gradient of 160℃-300℃, then carbonizes the pre-oxidized fiber at a low temperature of 300-800℃ in high-purity nitrogen, and finally carbonizes it at a high temperature of 1300-1600℃.
Rayon-based carbon felt processing technology
- Carbonization: After drying viscose nonwoven fabrics into the carbonization furnace heated to 300 ℃, carbonization heat from the furnace wire, the temperature first slow and then fast, to exclude volatile non-carbon components in the fiber, the formation of graphite-like microcrystalline structure of the carbonization process of carbonization fiber.
- Activation process: The viscose nonwoven fabricsafter carbonization is in the activation furnace, the heat for activation comes from the electric heating wire in the furnace, and then heated to about 1400 ℃ (furnace temperature) for activation, after activationthey become the phosphorus carbon fiber (activated carbon fiber crude products).
- Through-hole recycling: When the temperature of phosphorus carbon fiber is reduced to below 200℃, boiler steam is used to through-hole the phosphorus carbon fiber.
- Finished products into storage:Natural cooling of the carbon fiber after the through hole, packaged into storage.
Differences in Performance
1 Mechanical properties
PAN-based:
High strength and high modulus: good fiber orientation after carbonization, significantly better tensile strength (1.5-3.5 GPa) and modulus of elasticity (200-400 GPa) than rayon-based.
Abrasion resistance: more suitable for scenarios where mechanical stresses need to be endured.
Rayon-based:
Lower strength (tensile strength around 0.5-1.2 GPa) and lower modulus (40-100 GPa), but better flexibility.
2 Thermal properties
PAN-based:
Excellent high temperature resistance: long term resistance above 2000°C in an inert atmosphere (after graphitization).
Low coefficient of expansion and good dimensional stability.
Viscose-based:
Slightly inferior high-temperature performance: usually used at temperatures below 1500°C, but lower thermal conductivity at low temperatures, suitable for heat-insulating materials.
Low ash content (<0.1%), high purity, suitable for high vacuum or ultra-high temperature purification environment.
3 Electrochemical properties
PAN-based:
Better conductivity (resistivity about 1.5-2.5 μΩ-m), commonly used in fuel cell electrodes, supercapacitors, etc.
Viscose-based:
Higher resistivity (5-10 μΩ-m), but higher porosity (>90%), large specific surface area (500-1500 m²/g), suitable for adsorption or electrolyte wetting.
4 Application Scenarios
PAN-based carbon felts:
Structural reinforcement materials (e.g. C/C composites), high load electrodes, aerospace thermal protection.
Viscose-based carbon felts:
High-temperature insulation layer, vacuum furnace heat field, adsorption material (e.g. activated carbon felt), low-cost battery anode.