Study On Rheological Behaviors And Technology Of Wet-spinning Formation Of PAN/RTILs Concentrated Solutions

In the area of fiber materials, the wet-spinning technology of polyacrylonitrile (PAN) has been fully developed. The produced fiber not only has been used in clothes, but also in aviation, especially used as the precursor of carbon fibrer. But both in the process of wet or dry spinning, large amount of deleterious solvents, which are unfriendly to the environment, have been used. They could not meet the requirments of social development. Room temperature ionic loquids (RTILs) is a kind of new developing green solvent, having the advantagement of nonvolatility, good stability, wide liquid range and so on. RTILs have been used extensively in electronic chemistry, chemical reaction, and so on. In this paper, RTILs and PAN have been combined to study the rheological behaviors and the technology of wet-spinning formation of PAN/RTILs concentrated solutions, in order to discuss the technology of using RTILs as solvents in the production of PAN fiber.Two RTILs, BMIM-BF4 and BMIM-C1 have been chosen to dissolvePAN. The result of dissolution shows that BMIM-C1 could dissolve PAN at a lower temperature much more quickly and the solubility of PAN in BMIM-C1 is larger. It is interpreted that hydrogen-bond between PAN and BMIM-C1 could be the reason. However, BMIM-BF4 has worse solubility to PAN.Rotational rheometer has been used to study the rheological behaviors of PAN/RTILs concentrated solutions. The result shows that PAN/RTILs concentrated solutions are belong to pseudoplastic fluids. The non-Newtonian index of PAN/RTILs concentrated solutions decreases with increasing shear rates. In the BMIM-BF4, the viscosity of the solution decreases with decreasing molecular weight, increasing temperature and decreasing concentration. While the PAN/BMIM-C1 concentrated solutions exhibit special rheological behaviors, at high shear rates, the viscosity is much higher at high temperature, low concentration and low molecular weight. The reason is attributed to the high shear rates destroyed the hydrogen-bond between PAN and BMIM-C1.The wet-spinning formation of PAN/RTILs concentrated solutions has been performed on self-constructed spinning equipment. The factors that effect the properties of PAN fiber have been studied. The result shows that the properties of PAN fiber increase with increasing concentration of PAN in the solution. In this paper, the PAN fiber could posses the best properties when the conditions like these: theconcentration of spinning solution is 16wt%, the temperature of spinning solution is 70 °C, H2O is used as coagulating bath, the temperature of coagulating bath is 30°C. Compared to PAN/BMIM-C1 concentrated solutions, the spinnability of PAN/BMIM-BF4 concentrated solution is much worse.Zeng YuxingSupervised by: Zhang Yumei...