The effect of the chemical structure of spinnable pitches on their rheological properties and spinnability and the properties of carbon fibers produced from them

• L-SP with lower polymerization degree and longer alkyl side chains exhibits viscous-dominant rheology, promoting uniform stretching and maximizing carbon fiber properties. • H-SP with larger PAHs and higher branching shows balanced viscous-elastic behavior, leading to die swelling and surface irregularities despite better physical properties. • Both pitches yield carbon fibers with similar tensile strength and modulus, indicating that rheological properties critically influence fiber quality. • Optimal spinnable pitch should have high aromatic carbon content, small PAH size, and low C=O/O-C=O content to ensure viscosity-dominated flow and reduce defects.