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

A new variety of polyamide poly(m-phenyleneisophthalamide)(PMIA) was first prepared in 1962.Because of its excellent thermal and flame resistance properties,the papers and fibers made from it have been widely used in industrial and clothes applications.It plays an irreplaceable role in the field of high temperature resistance fiber.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 PMIA have been combined to study the rheological behaviors and the technology of wet-spinning formation of PMIA/RTILs concentrated solutions, in order to discuss the technology of using RTILs as solvents in the production of PMIA fiber.First,6 RTILs,such as 1-allyl,3-methylimidazolium chloride ([AMIM]Cl),and 1-butyl,3-methylimidazolium chloride([BMIM]Cl),etc were synthesized and characterized by means of FT-IR,NMR and qualitative elementary analysis.Dissolution of PMIA in these RTILs were investigated by means of PLM observation.Experimental results show that RTILs are non-derivatizing solvent,which effect dissolution by disrupting hydrogen-bond between PMIA and[BMIM]Cl and breaking the intramolecular network.Rotational rheometer has been used to study the rheological behaviors of PMIA/RTILs concentrated solutions.The result shows that PMIA/RTILs concentrated solutions are belong to pseudoplastic fluids.And the four different PMIA/RTILs solutions' viscosity are following:ηa([BMIM]Cl)>ηa([EMIM]Br)>ηa([BMIM]BF₄)>ηa([AMIM]Cl).It is interpreted that the difference of these four RTILs could be the reason.PMIA in the concentration range investigated exhibits very different behavior between[Bmim]Cl and DMAc/LiCl solvent.Unlike in DMAc/LiCl solvent,PMIA/[Bmim]Cl solution exhibits maxima in apparent viscosity- concentration plots in the range studied.The complex viscosity-frequency behavior of the PMIA/[Bmim]Cl solutions is similar to that steady-state rheological behavior. The different rheological behavior shows the interaction between macromolecule and IL which leading the supermolecular aggregates in PMIA/[Bmim]Cl solution.The reason of special rheological behavior is attributed to the high shear rates destroyed the hydrogen-bond between PMIA and[BMIM]C1.The wet-spinning formation of PMIA/RTILs concentrated solutions has been performed on self-constructed spinning equipment.The factors that effect the properties of PMIA fiber have been studied.The result shows that the properties of PMIA fiber increase with increasing concentration of PMIA in the solution.In this paper,the PMIA fiber could posses the best properties when the conditions like these:the concentration of spinning solution is 18wt%,the temperature of spinning solution is 90℃,H₂O is used as coagulating bath,the temperature of coagulating bath is 40℃.The structure and properties of PMIA fiber were studied by SEM,TGA etc,the result shows that the thermal properties of PMIA fiber are better than Nomex fiber.Results show that some RTILs are good solvents for PMIA.It is believed that the application of RTILs as solvents of PMIA will solve the pollution problem in PMIA industry and widen the application of PMIA.