Study On The Structure Regulation Of As-Spun Fiber In Dry-Jet Wet Spinning For PAN/DMSO Solution

In this thesis, the rheological behavior of PAN/DMSO solution wasstudied, firstly using rheological characterization method, the sheared andextensional rheological behavior of PAN/DMSO solution has beenstudied in detail, according to Tanner extrusion swell of viscoelastic fluidequation, the extrusion swell numerical simulation of spinning solutionhas been successfully implemented; using dry-jet wet spinning processfor preparation of PAN as-spun fibers, the surface and cross-section shapeand aggregation structure of PAN as-spun fibers were tested by means ofoptical microscope, SEM, AFM, and XRD, to studied the influence ofshear and stretch of PAN/DMSO solution; contrast the dry-jet wetspinning process with wet spinning process, elaborated the air layer indry-jet wet spinning coagulation process. The results show that:1. The viscosity of PAN solution increased exponentially withincreasing of concentration, while decreased linearly with the increasingof temperature; the viscosity decreased gradually with increasing shearrate with a turning point at high concentrations. 2. According to Tanner extrusion swell of viscoelastic fluid equation,numerical simulation of extrusion swell ratio was performed usingrheological data for PAN/DMSO solution.3. There is a viscoelastic transition point with increasing of shearrate for PAN/DMSO solution, which is decreased exponentially withincreasing of concentration, and increased linearly with the increase oftemperature.4. There is little effect of spinneret shear rate on the cross section ofas-spun fiber in dry-jet wet spinning of PAN/DMSO solution, however itis benefit to form a circular cross section by properly drawing in thespinning.5. The surface roughness of the as-spun fiber is affected by the shearrate and draw ratio. As the polymer solution entered to coagulation bath, asoft skin is formed, while the elastic recovery of polymer chain causedstress in the inner part of fiber, which gives rise to the roughness in thefiber surface. The surface roughness of the fiber decreases with increasingshear rate, and reached to a low point, then increased with increasingshear rate. With the increasing of draw ratio, the surface roughnessincreases gradually.6. No significantly effect of shear rate and draw ratio is found on thecrystallinity and grain size for the as-spun fiber. Higher orientation of thepolymer chain in the as-spun fiber is found at higher shear rate and draw ratio during the dry-jet wet spinning.