| In this paper, the process of coagulation in PAN wet-spinning was investigated in detail. Firstly, the reactivity ratios of comonomer were calculated. The composition and sequence distribution of copolymers were conjectured statistically. Secondly, the diffusion coefficients of solvent and nonsolvent were measured. Effects of coagulating conditions on diffusion coefficients and coagulating power were studied. And the concentration profiles of solvent in a moving filament during coagulation process were simulated. Thirdly, the thermodynamics of copolymer solutions were studied. The phase separation processes of spinning solvent were simulated by phase diagram. Lastly, effects of coagulating conditions on structure and properties of PAN nascent fibers were studied by electron probe microanalysis (EPMA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). And the formation mechanism of defects in PAN fibers was discussed.Values of monomers (AN with IA, MAA and AA) reactivity ratios were calculated by Q-e value. It can be found that the reactivity of carboxylic acid comonomers are higher than AN. Composition and sequence distribution of copolymers of AN with IA, MAA and AA as comonomers were simulated by Monte Carlo method. The results of simulation are consistent with the academic conclusion and as foreseen by the experimental data.Effects of coagulating conditions on diffusion coefficients in PAN wet-spinning were investigated. The diffusion coefficients of the solvent DMSO and coagulate H2O shows a trend of decrease with an increase of AN/IA copolymer concentration in the dope. With the bath temperature increase, the diffusion coefficients of DMSO and H2O increase continuously. As the jet stretch ratio increase, the diffusion coefficient of DMSO increases gradually, and the diffusion coefficient of H2O drops firstly and then increase. The diffusion coefficients of DMSO and H2O both show trends of great increase when the...
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