Manufacturing Process of Carbon Fiber

Manufacturing Process of Carbon Fiber
Anup Kumar Mohanta
Dept. of Textile Engineering
College of Engineering and Technology,
Bhubaneswar, Odisha, India
Email: anup.unlimited.007@gmail.com




CARBON FIBER:
Carbon fibers are manufactured from two pre cursors known as PAN (poly acrylonitrile) and pitch.

FROM PAN:
  • PAN contains highly polar C-N groups that are randomly arranged on either side of the chain.
  • Carbon filaments are wet spun from a solution of PAN and stretched at an elevated temperature during which the polymer chains are aligned in the filament direction. Then the filament are heated at 200 to 300 ­0C for a few hours. 
  • Structure of carbon fiber
    Structure of carbon fiber
  • At this stage the C-N groups located on the same side combine to form a more stable and rigid ladder like structure and some of the CH2 groups are oxidized.
  • In the next stage the PAN filaments are carbonized by heating at a controlled rate between 1000 to 2000 0C in an inert atmosphere.
  • Tension is maintained on the filament to prevent shrinkage and to improve molecular orientation.
  • Subsequently the carbonized filaments are heated above 2000 0C, where their structures becomes more oriented and turns towards a true graphite form with increasing heat treatment temperature.
  • At this stage the graphitized filaments attain a high tensile modulus, but their tensile strength may be relatively low.
  • Tensile strength can be increased by hot stretching above 2000 0C.
FROM PITCH:
  • Pitch is a byproduct of petroleum refining, and is a lower cost raw material than PAN.
  • The carbon atoms in pitch are arranged in low molecular weight aromatic ring patterns.
  • Heating to temperature above 300 0C polymerizes these molecules into long two dimensional sheet like structure.
  • The highly viscose state of pitch at this stage is called mesophase.
  • Pitch filaments are produced by melt spinning the mesophase pitch through a spinneret.
  • The filaments are cooled to freeze the molecular orientation and then heated between 200 to 300 0C in oxygen atmosphere to stabilize them and make them infusible.
  • In the next step the filaments are carbonized at 2000 0C.
  • Rest of process of transferring the structure to graphitic form is similar to that followed for PAN precautions.
Standard Fiber Properties
USES:
Carbon fibers are used in the following fields: Aerospace, sporting goods, automobiles, wind turbine blades, military, medical applications and many more fields.

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