Relationship Between Spinning Technology And Structure-Property Of Polyarylsulphonamide Fiber

Polyarylsulphonamide(PSA) fiber is applied as novel high-temperature resistant material in the high-tech fields of national defense and airspace.A series of polyarylsulphonamides were prepared with different monomer ratios by direct polycondensation based on the Schotten-Baumann reaction.The obtained polyarylsulphonamides had previously been chemically characterized by Fourier Transform Infrared Spectroscopy(FTIR). Sequence structures were investigated using Nuclear Magnetic Resonance(¹H-NMR and ¹³C-NMR).Theoretical strength and moduli of PSA fibers were calculated with simulation of the molecular structures by ChemSketch software.Thermo Gravimetric Analysis(TG) were performed to study on the relationships between structure and thermal behaviors.It demonstrates that the presence of relatively more flexible segments of m-phenylene in the polymer backbone do not sacrifice its thermal stability.So a favorable balance between processability and performance of polyaryisulphonamide copolymers can be achieved.The solubility of PSA in the ionic liquid 1-butyl-3-methylimidazolium chloride([Bmim]C1) and stability of molecular weight in different solvents were studied.It is shown that[Bmim]C1 is good solvent for PSA and the solutions are stable.Rheological behaviors were tested on Anto Paar MCR301 and HAAKE RS150L Cone-and-Plate Rheometers.Steady state shear and dynamic shear rheology of PSA/Dimethylacetamide(DMAc) and PSA/[Bmim]C1 solutions with different concentration were studied by measuring the apparent viscosity versus shear rate as well as the complex viscosity and dynamic moduli versus angular frequency at different temperatures.The typical rheological behavior of the polymer solutions were shown in these two different solvent systems.At low shear rate it behaves as Newtonian flow and non-Newtonian behavior is observed at high shear rate.The critical shear-thinning rate decreases with concentration increasing or temperature decreasing.The flow activation energy of PSA/[Bmim]C1 solutions(14%,52.1 kJ/mol) is much higher than that in PSA/DMAc(14%,17.9kJ/mol).Cox-Merz rule is not applicable at high shear rate.And gel point was not observed in PSA/DMAc solutions in our experiment,which suggests the stability.While the gel point of PSA/[Bmim]C1 solutions shift to lower frequency with increasing concentration and decreasing of temperature.It suggests that analogous setting of spinning technological parameters can be employed for PSA/[Bmim]C1 solutions and PSA/DMAc solutions.The evolution of the structure and morphology of PSA fiber during the spinning process were studied with synchrotron small-angle X-ray scattering(SAXS) and wide-angle X-ray diffraction(WAXD) technologies,thermal behaviors development was investigated by Dynamic Mechanical Analysis(DMA) and Thermo Gravimetric Analysis(TG),and mechanical property was also tested by the Strain-Stress(S-S)curves.It is shown that crystallinity and crystalline orientation of the PSA fiber enhanced obviously during the fiber-forming process,especially during hot-stretching and heat-setting procedure,with the increase in crystal plane spacing and crystalline grain sizes.The reduce of glass transition temperature(T_g) and initial decomposition temperature(T_i) after hot-stretching process revealed a probable damage of structure might occurred to the PSA fiber when drawn at high temperature.The tensile properties of PSA as-spun filaments were investigated by the temperature-controlled Stress-strain Tester.The effects of drawing rate,drawing ratio and drawing temperature on the tensile property were investigated by analyzing the characteristics of the tensile curves obtained at different drawing conditions.Development of structure and morphology for PSA as-spun filament during drawing process was studied by synchrotron WAXD techniques.It is shown that the strength increased with the increase of drawing ratio until 2.2 while the corresponding elongation decreased.The tenacity of PSA filament enhanced when drawn at higher tensile rate until 30mm/min and reduced dramatically at tensile rate of 40mm/min.The effect of increasing the drawing temperature on tensile property equals to that of decreasing the drawing rate in the cold-drawing process.Analyzing the WAXD patterns shows that crystalline orientation of PSA as-spun filament improved significantly when drawn up to strain of 220%.The tensile properties is dependent largely on the drawing conditions and the crystal and orientation structure developed with the drawing procedure,which suggests that the mechanical properties can be improved through effective drawing process.