Rheological Properties Of PAN/DMSO Solution And Its Effect On The Structures Of As-spun Fiber

The thesis studied the effect of spinning solution component on the spinnability(including non-Newton index,activation energy and visco-elastic transition point),explored relationship between extrusion shear rate and morphology(surface and cross-section) & aggregation structure of PAN as-spun fiber & residues of DMSO in the as-spun fibers,and analyzed the process of phase departure of PAN/DMSO solution through rotary rheometer, scanning electron microscopy(SEM),X-ray diffraction(XRD),UV-Vis spectrophotometer and optical microscope etc,using the earlier knowledge about rheological properties of PAN/DMSO solution as a foundation.Rheological properties of PAN/DMSO solution as important factors were the impacts of PAN fiber formation of wet spinning.Corresponded with lower extrusion shear rate and solution component,higher temperature,there had been a higher non-Newtonian index;higher solution component and lower extrusion shear rate corresponded to higher activation energy;lower temperature and higher solution component corresponded to lower visco-elastic transfers(frequency).Extrusion shear rate not only effected macromolecular shape in the spinning hole,but also influenced morphology and aggregation structure of PAN nascent fiber.The results showed that crystallinity of fibers increased with improving the rate of shear in the PAN/DMSO solution,but the crystal size reduced when enhancing the rate of shear.The pictures from scanning electron microscope demonstrated that puckers along the fiber axis could also be produced in the surface of fiber,the depths and regulations of these puckers would be strengthened,while increasing the rate of shear,some holes and skin-core structures were observed in the cross-sections of fibers.The residual DMSO amount in the as-spun fibers increased with improving the rate of shear simultaneously.It could be concluded that the optimal rate of shear should be about 10000s^-1 for gaining an outstanding rheological property of spinning solution;compacted and uniform fibers with homogeneous puckers; little defect;small crystal size and high crystallinity.Studied the effect of time,bath concentration and solution component of PAN/DMSO solution on the process of phase departure in no-shear,the results showed that coagulation layer thickness was directly proportional to the square root of time;as time increased,coagulation layer thickness increased, coagulation rate unchanged;with the bath concentration and solution component increasing,both coagulation layer thickness and coagulation rate were reduced,and the PAN solid phases had less pore and solid structure were compacted and uniform.