Investigating the jet stretch in the wet spinning of PAN fiber

Abstract

The jet stretch of wet-spun PAN fiber and its effects on the cross-section shape and properties of fibers were investigated for the PAN-DMSO-H 2 O system. Evidently, the spinning parameters, such as dope temperature, bath concentration, and bath temperature, influenced the jet stretch. Also, under uniform conditions, the postdrawing ratio changed as well as that of jet stretch. When coagulation temperature was 358C simultaneously with bath concentration of 70%, jet stretch impacted obviously the cross-section shapes of PAN fiber, but had little effect when the temperature was below 108C or above 708C. As the jet stretch ratio increased, the crystallinity, crystal size, sonic orientation, and mechanical properties of the as-spun fiber changed rapidly to a major value for jet stretch ratio of 0.9 where the cross section of as-spun fiber was circular. With further increasing of jet stretch ratio, the properties changed slightly but the fiber shape was not circular. The results indicated that appropriate jet stretch, under milder formation conditions in wet-spinning, could result in the higher postdrawing ratio and circular profile of PAN fiber, which were helpful to produce round PAN precursor with minor titer and perfect properties for carbon fiber.

Properties of PAN Fibers Solution Spun into a Chilled Coagulation Bath at High Solvent Compositions

“…The draw down ratio is defined as the ratio of the tow velocities, exiting-to-entering the zone of interest. The spin draw (sampling point I), or draw applied during coagulation, calculated from the apparent entering and exiting velocities, was less than 1, which has been observed by others [12][13][14][15][16][17]. The tow velocity entering coagulation was calculated using the known, constant volumetric flow rate of the dope, and the dimension of the spinneret, and was used, uncorrected for viscoelastic die swell of the extruded jets, for the velocity calculation.…”

Investigation the jet stretch in PAN fiber dry‐jet wet spinning for PAN‐DMSO‐H2O system

“…These differ from the results in wet spinning process of our previous work. 10 In wet spinning, below bath concentration of 30 wt %, the maximum jet stretch and postdrawing ratio decrease with increasing bath concentration, but increase as bath concentration increases upto 70 wt %. Furthermore, the influence of bath concentration in wet spinning is more conspicuous.…”

“…In our previous study, 10 we investigated experimental process and results of jet stretch in wet spinning. It was found that jet stretch ratio had key effect on postdrawing process, and a too great increasing of the jet stretch decreased the properties of as-spun fiber and PAN fiber, also decreasing postdrawing ratio.…”

“…But in both spinning processes the postdrawing ratio is not very high and is influenced by jet stretch. 10 Like postdrawing process, the jet stretch step is very important in altering fiber structure and enhancing fiber properties. In wet spinning, the extruded dope is brought into coagulation bath such that the exchange between the solvent and nonsolvent takes place until the polymer precipitates.…”

Effect of Bath Concentration on Coagulation Kinetics at the Early Stage during Wet Spinning of PAN Copolymer Nascent Fibers

“…[3][4][5][6][7][8][9][10][11][12] The influence of coagulation conditions on the coagulation process during the wet spinning of PAN nascent fibers have also been reported. [13][14][15][16] However, the mechanisms of the coagulation during wet spinning are not yet well understood.…”