Influence of Guanidine Crotonate on the Rheological Properties of Polyacrylonitrile Fiber Spinning Solution in Sodium Thiocyanate System

ABSTRACT The preparation of high‐quality carbon fiber precursor filaments requires not only excellent properties of the polyacrylonitrile (PAN) polymer itself but also insight into the molecular behavior of the polymer solution. Studying PAN and its spinning dope is of great significance. In this study, the P(AN‐co‐GCA) copolymer and its spinning solution were prepared by using the novel comonomer guanidine crotonate (GCA). The structure, thermal behavior, and rheological properties of P(AN‐co‐GCA) were investigated by Fourier‐transform infrared spectroscopy (FT‐IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and rotational method. The results of the TGA and contact angle tests show that the incorporation of GCA leads to an 82% increase in the mass residue rate of the P(AN‐co‐GCA) copolymer and enhances its hydrophilicity by at least 16.7%. The optimal mass fraction of sodium thiocyanate (NaSCN) aqueous solution is approximately determined to be 51 wt%. The introduction of GCA reduces the zero‐shear viscosity of the PAN polymer solution by more than 40.6% and the structural viscosity index by more than 15.8%, which contributes to the improvement of the spinnability of the polymer solution. This provides a reference for further optimizing the polymer solution in the NaSCN aqueous solution system.