Studies on polyacrylonitrile/cellulose nanocrystals composite precursor and carbon fibers

In this study, PAN fibers containing up to 40 wt% CNC were spun by gel-spinning technology. The structure, morphology, and mechical properties of PAN/CNC precursor and their carbon fibers have been studied. The results show that the H2O/dimethyl formamide (DMF) co-solvent disperses individual CNCs more effectively than pure H2O or pure DMF, especially at high CNC concentrations. The addition of CNCs improves the tensile modulus of PAN fibers at a low draw ratio. The fully drawn PAN/CNC fibers containing even the 40 wt% CNCs exhibit the same strain to failure as the fully drawn PAN fibers. The high orientation of CNCs in PAN fibers was observed by Raman spectroscopy, in which the 1095 cm−1 Raman band of CNCs shows a two-fold symmetry under vertical/vertical (VV) mode and a four-fold symmetry under vertical/horizontal (VH) mode. With the addition of 40 wt% CNC, the activation energy of cyclization and crosslinking reactions of PAN is reduced by 17.5 and 19%, respectively. The carbon fibers made from PAN containing 20 wt% CNCs show the tensile strength of 2.3 GPa and the tensile modulus of 252 GPa, which are comparable to the PAN based carbon fiber properties (tensile strength of 1.9 GPa and tensile modulus of 251 GPa) processed under the same conditions.