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为制备适于干 -喷湿纺用PAN(polyacrylonitrile)纺丝溶液 ,选用了较高粘均相对分子质量的PAN ,通过测定纺丝溶液的回转粘度 ,对其流变性能进行了较为详尽的研究。研究结果表明 :粘均相对分子质量为近 2 0万的PAN溶液为切力变稀型流体 ,具非牛顿性。在40~ 80℃的温度范围内 ,浓度为 18%~ 2 0 %的纺丝溶液的临界切变速率为 10 0 9~ 10 1 7。提高纺丝溶液的浓度可使溶液的粘流活化能 (Eη)及结构粘度指数 (Δη)增大、非牛顿指数 (n)减小 ;溶液温度升高则会导致n的增大和Δη的减小 相似文献
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主要探讨了纳米负离子在聚丙烯腈溶液中的分散问题,并讨论了纳米粉体对聚丙烯腈相对分子质量、溶液流变特性的影响。结果表明:添加顺序对纳米级负氧离子粉体在聚丙烯腈干法纺丝原液中的分散有很大影响,在溶胀前加入纳米负离子粉体的分散效果最佳;随着粉体含量的增加,分散效果降低,粉体含量<3%时分散性较好;负离子粉体的加入使得原液的黏度有所降低,黏流活化能有所增加;但在较高剪切速率下,黏度随温度的变化不明显,且黏流活化能也接近常规PAN原液。 相似文献
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The restriction of the zone of stationary jet flow of LC sulfuric-acid solutions of PPTA and the conditions of stable spinning
of fibres with small air gaps using spinnerets with small-diameter channels is explained with the well-known theory of resonance
in drawing for viscoelastic, non-Newtonian media in continuation of the effect of shear flow in the channels on longitudinal
flow in the jets. In spinning fibres from 19.5% LC sulfuric acid solutions of PPTA and copolyamide, drawing of the jet in
the spinning bath supplements drawing of the jet in the air gap. The former is slight and is a function of the stress created
in deformation of the LC solution in the air gap, area of the jet cross-section on the surface of the spinning bath, and type
of polymer. The conditions of extreme spinning regimes with breaks in PPTA and polyamide monofilaments in the spinning bath
medium in the absence of resonance in drawing of the jet in an air gap are presented.
Terlon Co., Mytishchi. Translated fromKhimicheskie Volokna, No. 1, pp. 12–16, January–February, 1999. 相似文献
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S. J. Shilton 《应用聚合物科学杂志》1997,65(7):1359-1362
A methodology is presented to establish the flow profile induced in a spinneret during the spinning of hollow fiber membranes. The flow equations are derived for a power law fluid passing through a concentric annulus. The pressure drop, the velocity profile, the shear stress profile, and the shear rate profile induced during spinning can then be determined. This type of rheological knowledge is useful if membrane structure and properties are to be related to the flow conditions experienced in the spinneret. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1359–1362, 1997 相似文献
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The effect of aluminium stearate on the rheological behavior of ultra-high molecular weight polyethylene (UHMWPE) semidilute solutions with paraffin oil as the solvent has been investigated. Adding aluminium stearate to paraffin oil can prevent the spinning solution from adhering to the pipe or screw, greatly improving the flow behavior of UHMWPE solutions. The geometric sizes of spinnerette hole, such as length–diameter ratio L/D and entrance angle of a capillary, also affect the flow behavior of the spinning solution. The calculated first normal stress difference σ11 ? σ22 and the Bagley-end correction e from experimental data show that the elastic effect on spinning solutions in flow is quite large, although the shear rate is below 20 s?1. 相似文献
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Investigation of shear effects on styrene free radical polymerization using a narrow channel reactor
Spinning disc reactor technology has been demonstrated to achieve significant enhancements in the rates of free radical polymerization. It is believed that these enhancements are related to the centrifugal and shear conditions that exist on the disk and it is the objective of this study to elucidate the role of shear in thin films in a plug flow regime. Polymerizing systems have been subjected to shear fields in the range of 0.4 to 2,173 s?1 and comparisons between conversion profiles and polymer product properties have been made. It has been found that shear fields have little or no effect on these systems while the reaction is in the kinetically controlled regime and it is concluded that the observed rate enhancements of free radical polymerization on a spinning disk are not largely attributable to the high rates of shear experienced by the thin film as it traverses the disk. Our studies therefore continue to assess the role of flow divergence and centrifugal extension in the kinetics of polymerization. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94:1365–1369, 2004 相似文献
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The dynamics of melt spinning was examined in the case of a Lethersich liquid taking also into account a phenomenologic way as well the transition zone between shear and elongational flow. The shape of the fluid jet was measured under many spinning conditions; the filament temperature and the fluid viscosity were then calculated. The experimental viscosity temperature relationship was compared with the W. L. F. equation, and the comparison makes it clear that the Newtonian model is not adequate whereas all the experimental evidence is in qualitative accordiance with the proposed model. 相似文献
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采用新型碱复合溶剂NaOH/硫脲/尿素水溶液作为溶剂溶解纤维素,对纤维素溶液的流变性能进行探索,从而为纤维素/NaOH/硫脲/尿素溶液纺丝提供理论依据。研究结果表明,纤维素溶液表现出非牛顿流体的性质,溶液的粘流活化能随纤维素质量分数以及剪切速率的不同而有所差异,纤维素溶液的结构黏度指数随着温度的升高、纤维素质量分数的增大而增大。5~25℃是所测的纤维素溶液纺丝的适宜温度范围,随着温度的升高,凝胶点开始出现,且凝胶点随着温度的升高向高频率的方向移动。随着纤维素质量分数的增大,纤维素溶液凝胶温度降低。 相似文献
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The rheological behavior of polyurethane (PU)/N,N‐dimethylformamide (DMF) spinning solutions with various contents of hyperbranched polyesters was studied using a RS150L‐controlled stress rotational rheometer. The results showed that the viscosity of the spinning solutions could be greatly reduced by adding hyperbranched polyesters even at 0.5 wt% loading. The zero‐shear viscosity of solutions with hyperbranched polyesters was much lower than that of pure PU/DMF solution, which indicated a lower degree of entanglement when solutions were in a static state. The apparent activation energy of viscous flow and the critical shear rate for shear thinning of solutions with hyperbranched polyesters were much lower than that for pure PU/DMF solution, which indicated a weaker entanglement structure formed. In addition, the effect of hyperbranched polyesters on the mechanical properties of Spandex fiber was discussed. Copyright © 2006 Society of Chemical Industry 相似文献
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采用RT-2000毛细管流变仪,研究了海藻酸钠(SAL)/羧甲基壳聚糖(CMCS)纺丝溶液的流变性能。结果表明:SAL/CMCS纺丝溶液是切力变稀型流体,随着剪切速率(γ)的增加,纺丝溶液的表观粘度(η_a)下降;随着纺丝液中CMCS含量的增加,SAL/CMCS纺丝溶液的η_a和结构粘度指数(△η)下降,非牛顿指数(n)增大;随着纺丝液温度的升高,SAL/CMCS纺丝溶液的η_a和△η下降,n增大。纺丝过程中应控制SAL/CMCS纺丝溶液的温度为35℃,纺丝溶液中CMCS质量分数为15%较适宜。 相似文献
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Study on spinnability of polyacrylonitrile solution based on dynamics simulation of dry‐jet wet spinning 下载免费PDF全文
Spinnability of polyacrylonitrile (PAN) solution was studied based on the spinning dynamics simulation and dry‐jet wet spinning experiments. The spinnability phenomenon was observed from the extruding and extending spinning experiments. The suitable conditions of normal extruding and extending of the PAN solution were obtained and the critical spinnability conditions were simulated. The experimental and simulation results showed that pressure drop through the spinneret was similar, while the temperature, velocity, and velocity gradient through the spinneret of PAN solution changed dramatically. It suggests that pressure drop can be chosen as one of the spinnability criterion for solution extruding and filaments forming during dry‐jet wet spinning. Furthermore, the effect of spinneret parameters and spinning conditions on spinnability was simulated. It shows that spinneret entrance angle, outlet channel length and width have impacts on the pressure drop and the die swell ratio, which suggests the spinneret design can be optimized to regulate the spinnability according to the simulation results. It is also found that some bad situations of spinnability such as sticking phenomenon can be avoided by decreasing spinning temperature or increasing mass flow rate to increase the pressure drop at a certain level under the premise of extruding smoothly. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46377. 相似文献
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《Drying Technology》2013,31(7):1335-1359
Drying behavior of acetate filament in dry spinning is investigated, including the elongational deformation of polymer solution thread in the early stage of drying. Variations of diameter, velocity, temperature, solvent concentration profile in the thread and tension distribution along the threadline in the spinning column, are calculated for spinning conditions encountered commercially by means of the equations of simultaneous momentum, heat and mass transfer between the thread and hot air flow in the spinning column. Concentration and temperature dependencies of the mutual diffusion coefficient from desorption experiment are correlated by the free volume theory. The elongational viscosity is estimated from the shear viscosity data using Krevelen theory. Residual acetone concentratio in the thread and tension at the exit of the spinning column are compared between the calculated results and the experimental data by a commercial apparatus; satisfactory agreement is found. Rapid decreases of temperature and surface concentration of the dope thread after extrusion confine the elongational deformation within several centimeters below the spinnerette. Initial elongational rate and die swell ratio are related to the winding velocity and tension at the exit of the spinning column. The tension is determined mainly by initial viscous force and air drag. 相似文献
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Yuji Sano 《Drying Technology》2001,19(7):1335-1359
Drying behavior of acetate filament in dry spinning is investigated, including the elongational deformation of polymer solution thread in the early stage of drying. Variations of diameter, velocity, temperature, solvent concentration profile in the thread and tension distribution along the threadline in the spinning column, are calculated for spinning conditions encountered commercially by means of the equations of simultaneous momentum, heat and mass transfer between the thread and hot air flow in the spinning column. Concentration and temperature dependencies of the mutual diffusion coefficient from desorption experiment are correlated by the free volume theory. The elongational viscosity is estimated from the shear viscosity data using Krevelen theory. Residual acetone concentratio in the thread and tension at the exit of the spinning column are compared between the calculated results and the experimental data by a commercial apparatus; satisfactory agreement is found. Rapid decreases of temperature and surface concentration of the dope thread after extrusion confine the elongational deformation within several centimeters below the spinnerette. Initial elongational rate and die swell ratio are related to the winding velocity and tension at the exit of the spinning column. The tension is determined mainly by initial viscous force and air drag. 相似文献
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采用原位聚合的方法制备了纯聚酰胺酰亚胺(PAI)及PAI/羧基化多壁碳纳米管(MWCNTs-COOH)复合材料(NCs),并采用热重分析仪和旋转流变仪分别研究了两种材料的热稳定性以及温度和溶液浓度对其溶液流变行为的影响。结果表明,MWCNTs-COOH的加入提高了NCs的热稳定性。纯的PAI溶液对剪切速率、温度不敏感;而NCs溶液对剪切速率较为敏感,发生了剪切变稀现象,但是在较高温度或较高浓度及低剪切速率下仍有稳定的流动性;在测试范围内,两种溶液体系的损耗模量高于储能模量,表明黏性占主导地位,不会发生凝胶现象。浓度,温度,剪切速率对PAI溶液的流动性影响较小,纺丝条件较为温和,但在高温高角频率区易发生复数黏度增大的现象;而在温度75℃或90℃、溶液浓度10%且剪切速率较低时,NCs溶液流动性稳定,适宜纺丝。 相似文献