What happens during the pyrolysis of polyacrylonitrile?

The Transformation of Polyacrylonitrile

When creating high-performance carbon fibers, the journey starts with a specialized polymer known as polyacrylonitrile, or PAN for short. Transforming this raw material requires a precise, multi-step thermal process.

The first major phase is stabilization, often called oxidation. During this stage, the PAN fibers are systematically stretched while being exposed to temperatures ranging between 200 °C and 300 °C. This critical heat treatment fundamentally changes the material's chemical structure, converting what was once a thermoplastic polymer into a heat-resistant, non-plastic cyclic or ladder-like compound. This ensures the fiber maintains its shape and integrity under extreme heat.

Following successful oxidation, the fibers move into the carbonization phase. Here, they are heated to approximately 1000 °C inside a carefully controlled, inert environment—typically filled with nitrogen gas to prevent unwanted burning or reactions. This intense heat drives away non-carbon elements like hydrogen, nitrogen, and oxygen, leaving behind a tightly bound, exceptionally strong structure composed almost entirely of carbon.