Polycondensation‐Derived High‐Molecular Weight Lignin as Nonblended Precursor for Carbon Fibers

Abstract A new concept for the controlled chain‐extension of lignin has been developed. A mixture of trioxane as formaldehyde source, resorcinol as chain extender, and lignin allows to prepare high molecular weight precursor fibers by melt‐spinning, which can be spun on a semitechnical scale. Chain extension with resorcinol bridged by methylene groups is achieved during the stabilization process of the precursor fiber. After carbonization, carbon fibers (CFs) with an average diameter of 18 µm show an average tensile strength of 0.78 GPa and a Young's modulus of 106 GPa. A maximum tensile strength of 2.44 GPa and a Young's modulus of 294 GPa are reached with fibers 9.7 µm in diameter.