How carbon fiber is made

Carbon fiber is a plastic thread baked until everything but the carbon has been driven out of it.

stations: 6
things upstream: 8
raw sources: 4
steps from the ground: 4

The short version

Carbon fiber is made from a plastic precursor, usually polyacrylonitrile. The plastic is spun into filament yarns that are stretched to align the chains, then heated in stages so that all non-carbon atoms are driven off. What is left is a thread of nearly pure carbon, about 5 to 7 micrometers thick, which is coated and wound on spools.

Make the acrylic precursor

Propylene and ammonia are converted to acrylonitrile, which is polymerized into polyacrylonitrile, or PAN. This plastic is the raw material for most carbon fiber.

Goes in
Propylene Ammonia
Spin it into filament

PAN solution is pushed through spinnerets into a coagulating bath, forming bundles of filaments. Stretching the yarn aligns the polymer chains, which gives the finished fiber its strength.
Stabilize it in air

Filaments pass slowly through ovens full of hot air. The chains rearrange into a heat-proof form, and the fiber turns from white to black.

Goes in
Air
Carbonize it without oxygen

In a furnace filled with inert gas, the fiber is heated until nitrogen, hydrogen and oxygen atoms leave. Only tightly bonded sheets of carbon atoms remain.
Treat and size the surface

The fiber is lightly oxidized so resin can grip it, then coated in a thin protective sizing. This helps the fiber bond with epoxy later.
Wind it onto spools

Thousands of filaments are bundled into a tow and wound onto spools. Weavers and composite makers buy it as tow or as woven cloth.

End of the lineCarbon fiber Next it goes into wind turbine, camera drone, satellite and 7 more.

Worth repeating

The Airbus A350 XWB is 53% carbon fiber reinforced polymer by weight, including wing spars and fuselage parts.
Carbon fiber can be made from polyacrylonitrile, rayon or petroleum pitch.