Mechanics of steady flow in coextrusion fiber spinning

The steady flow of isothermal bicomponent coextrusion fiber spinning has been investigated. A model has been chosen in which a Newtonian fluid and a Phan-Thien/Tanner (PTT) fluid were considered to be the core and the skin layer, respectively. This model was adopted to study the effect on spinline velocity of an interaction between two fluids with quite different extensional rheology. The effects of the hoop stress, gravity, inertia, and surface and interfacial tensions were disregarded. Only viscous and viscoelastic forces were considered. A uniaxial extension was also assumed as the radius variation in the axial direction is small. The Newtonian fluid has been considered prone to fluctuate during melt processing while the viscoelastic skin layer has a stabilizing effect. The velocity profile was affected by the choice of two characteristic parameters: extensional and shear-thinning parameters, as well as the viscoelastic skin flow rate ratio. Both shear-thinning and extensional parameters play important roles in melt flow. The results show that as the draw ratio increases, the system is dominated by the extensional parameters, whereas slow drawing is dominated by shearing, in spite of the thin viscoelastic skin.     

Stability of fiber spinning of power-law fluids

A stability analysis of fiber spinning of isothermal power-law fluids has been carried out. The analysis for purely viscous fluids indicates that the critical extension ratio increases with an increase in power-law constant q above 1. For q greater than approximately 1.5, very high values of critical extension ratio are obtained. A stability analysis in the presence of viscous and inertial forces indicates that for q > 1 critical extension ratio can be correlated to a quantity Rq = q ? 1 + 3Re, wherein Re is the Reynolds number. For the values of Rq greather than approximately 0.5, very high values of critical extension ratios are obtained.     

Theoretical aspects of fiber spinning

A new coordinate expansion based on a Taylor series is used to derive the one‐dimensional approximation to unsteady isothermal jet flows. The expansion procedure is carried out for an isothermal, Newtonian jet with no surface tension and air drag, and it can be used to derive a higher order approximation to the flow field. Two new formulations have been derived for the eigenvalue problem for fiber spinning stability for negligible inertia and gravity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 986–993, 2004     

熔体直纺涤纶平行纺管道输送的设计

介绍了熔体直纺涤纶平行纺输送管道设计过程,及熔体流量、熔体管道压力降、熔体管道停留时间、管道壁厚的选择等计算方法及设计要点。     

A study of fiber extrusion in wet spinning. II. Effects of spinning conditions on fiber formation

A study is carried out to investigate the effects of spinning conditions on fiber formation in the wet-spinning process. The spinning conditions studied are free velocity (and hence free diameter), throughput rate, maximum take-up velocity, jet stretch (the ratio of take-up velocity to free velocity), and filament tension. The coagulating bath temperature and concentration are varied, and three spinnerette diameters are used. The spinning dope is an aqueous solution of polyacrylonitrile in sodium thiocyanate. The present study shows that the coagulating bath concentration influences the spinning tension and maximum take-up velocity. Two thread breakage mechanisms are postulated which take into account the rate of coagulation, spinning tension, and thread velocity. An attempt is made to predict the concentration profile of solvent in the moving filament by simultaneously solving the mass and force balance equations, in which the increase in elongational viscosity along the spinning way is assumed to be mainly due to the hardening process.     

熔体静电纺丝的工艺条件对纺丝纤维直径的影响

主要研究纺丝温度、纺丝电压、接收距离等参数对聚丙烯(PP)熔体静电纺丝纤维直径的影响。采用了只变一个参数,其它参数固定的常规实验方法。在实验条件范围内,随着纺丝温度的升高,纤维的平均直径逐渐减小,得到PP的最佳纺丝温度240℃。在固定电压的情况下,得到最佳接收距离7cm。在固定接收距离的情况下,随着电压的增加,电场中的喷射流熔体受到的电场力逐渐增大,得出最佳纺丝电压35kV。     

Stability of isothermal spinning of viscoelastic fluids

The stability of isothermal spinning of viscoelastic fluids which have strain-rate dependent relaxation time has been investigated using the linear stability analysis method. The instability known as draw resonance of the system was found to be dependent upon the material functions of the fluids like fluid relaxation time and the strain-rate dependency of the relaxation time as well as upon the draw-down ratio of the process. Utilizing the fundamental physics of the system characterized by the traveling kinematic waves, we also have developed a simple, approximate method for determining this draw resonance instability; it requires only the steady state velocity solutions of the system, in contrast to the exact stability analysis method which requires solving the transient equations. The stability curves produced by this simple, fast method agree well with those by the exact stability method, proving the utility of the method. The stability of other extensional deformation processes such as film casting and film blowing can also be analyzed using the method developed in this study.     

熔体直纺上纺制多功能聚酯纤维的设备改造

介绍了在熔体直纺生产线上,生产在线可控多功能聚酯纤维的生产工艺流程、设备改造,熔体直纺在线添加技术的关键点,采用球窝型动态混合器对添加组分进行均匀混合。改造后生产高附加值的功能纤维,产品品质达到用户要求。     

抗起球腈纶纺丝工艺的优化

采用纺丝工艺调整法生产抗起球腈纶。结果表明:在抗起球腈纶生产工艺基础上,选择孔径相对较小的喷丝板,提高负拉伸比,有利于纤维成形;干燥机丝束堆积密度下调3%,湿球温度上调至77～80℃,采用加压过热蒸汽为热定型介质,热定型温度110～115℃,生产的抗起球腈纶抗起球级数达4.0～4.5。     

Simulations of instability in fiber spinning of polymers

This work determines the critical regimes beyond which the melt fiber spinning for noncrystallizable polymeric liquids becomes unstable. The critical draw ratio of the process is established using linear stability analysis for both isothermal and nonisothermal fiber spinning regimes. In addition, nonlinear isothermal analysis describes the complete range of the stable and unstable conditions for fiber spinning. Unlike previous studies, this research uses quite realistic viscoelastic constitutive equations extensively tested for five polymer liquids, which provides a good comparison of our calculations with available experimental data. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Gel spinning of PVA/SWNT composite fiber

Single wall carbon nanotubes (SWNT), polyvinyl alcohol (PVA), dimethyl sulfoxide (DMSO) and water, homogeneous dispersion has been prepared by stirring and sonication. This dispersion was extruded into fiber via gel spinning. The modulus of the PVA/SWNT (3 wt%) composite fiber was 40% higher than that of the control PVA gel spun fiber. Fiber structure and properties have been studied. The PVA orientation in the control and the composite fibers were comparable while the composite fiber exhibited lower crystallinity.     

Fabrication of segmented cladding fiber by bicomponent spinning

Fabrication of segmented cladding fiber (SCF) by bicomponent spinning was proposed in this article. In the new designed spin pack, we considered the high refractive component of cladding and core as a whole to control the cross section of the fiber. Quenching system in current bicomponent melting spinning system was modified according to the requirement of quenching fiber with a large size. The polymer SCF with required cross section was successfully fabricated using polycarbonate and polymethyl methacrylate. The transmission loss in the wavelength of 500–1000 nm was tested by the cut‐back method. The result showed that the transmission loss of the obtained fiber was comparatively high, being up to 30 dB/m. The output light pattern of the obtained fiber of 60 cm was collected by using a charge‐coupled device camera with laser light of 532 nm as the input. The output light pattern for the far field was a uniform circle and that for the near field was similar to the cross‐section designed. The results showed that the obtained fiber was still a multimode optical fiber because of the comparatively large refractive index difference between the two materials used. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

腈纶纺丝生产线控制系统的改造

介绍了合肥工业大学采用西门子公司的PLC和爱默生公司的矢量控制变频器等硬件,使用了开放现场总线PROFIBUS-DP,成功研制和改造了中石化安庆分公司腈纶纺丝线及备用线的电气控制系统。新设计的腈纶纺丝线电气控制系统整体性能优于原系统,达到了降低能耗、降低故障率,提高产品产量和质量的目的。     

彩色夜光聚丙烯纤维纺丝工艺探讨

以熔体流动指数为每10 min 40g的聚丙烯(PP)为原料,以稀土长余辉蓄光型夜光粉和原液着色颜料为添加剂,采用独特的分散技术,使夜光粉和颜料与PP基体充分混合均匀;以添加夜光粉质量分数5%的PP为皮层,颜料质量分数1%的PP为芯层,通过皮芯复合纺丝,纺制彩色夜光PP纤维,探讨了其纺丝工艺条件。结果表明:当夜光粉粒径小于等于4μm,皮芯质量比40∶60,纺丝温度230℃,拉伸倍数4.0时,纺丝顺利,纤维性能较好;纺制的167 dtex/24 f彩色夜光PP纤维夜光效果达到吸光15 min,持续发光肉眼可见超过10 h,纤维的力学性能达到丙纶拉伸丝一等品标准。     

海岛复合超细纤维的纺丝工艺探讨

采用特性粘数0.70dL/g以上的水溶性聚酯(COPET)为海组分,半消光聚酯(PET)为岛组分进行纺丝,得到海岛复合超细纤维,探讨了纺丝工艺对纤维染色性能的影响。结果表明:应严格控制干燥条件及纺丝组件工艺,干切片含水量小于30μg/g,岛组分与海组分粘度差0.02dL/g,COPET纺丝温度273～286℃,PET纺丝温度289～295℃,冷却吹风速率0.45～0.50m/s,吹风温度18～20℃,卷绕速度3300m/min,可得到染色性能好的海岛复合超细纤维。     

The effect of reprocessing of polypropylene on fiber spinning

Because of the environmental considerations, recycling is becoming a very important factor in any production planning within the fiber industry and textile industrial sectors. One of the determining factors for recycling of fibrous assemblies into fiber is the spinnability of the incoming material. The hypothesis underlying the present work is that by carrying out rheological analysis of the polymer melt it should be possible to predict the state and level of degradation of the polymeric fibrous waste material—hence its spinnability. Our experimental studies show that a melt spinning grade polypropylene could be recycled five times without significant decreases in fiber properties. Afterward, the fiber production failed in the cold-drawing step before melt rupture occurred in the draw-down step. Rheological analysis of the melt in long-term stability experiments showed that unspinnable melts show an abrupt change in loss factor at a certain level of loss and storage modulus. The reasons for this behavior are associated to changes in molecular weight, viscosity, and melt strength. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1859–1867, 1999     

纺丝速度对聚乙交酯纤维结构的影响

采用差示扫描量热法(DSC)、广角X射线衍射(WAXD)、热失重(TGA)和偏光显微镜(PLM)等方法对聚乙交酯(PGA)纤维的结构进行了分析。DSC和WAXD分析表明,低速纺丝高倍后拉伸的纤维结晶结构较为完善,而高速纺丝低倍后拉伸的纤维结晶状态较差。TGA和PLM分析表明,低速纺丝高倍后拉伸纤维的热稳定性能优于高速纺丝低倍后拉伸的纤维。采用低速纺丝高倍后拉伸的工艺路线可以得到具有较好结构的PGA纤维。     

正十字形涤纶短纤维纺丝工艺探讨

讨论了影响正十字形涤纶短纤维充满度及纤维质绩的工艺因素采用喷丝板正十字形孔长宽比为7:1和合理的排列方式,冷却吹风距离70 mm,风速1.2 m/s,风温20℃.纺丝温度275-280℃,纺丝速度900-1 000m/min,拉伸温度55℃,紧张热定型温度120-150℃,松弛热定犁温度70-90℃,生产的2 22 dtex 正十字形涤纶短纤维质量优良,充满度为55%     

Ripening time and fiber formation of chitosan spinning dope

A study was carried out on the wet spinning of chitosan fibers using 2% acetic acid as a solvent, 10% aqueous sodium hydroxide as a nonsolvent, and 4% chitosan solution as a polymer concentration. In this study, we investigated the effect of the ripening time of the spinning dope on the ability of fiber formation (i‐value), structure, thermal, and mechanical properties (such as fineness, tenacity, elongation, work of rupture, etc.) of chitosan fibers. Based on the results, it can be seen that the ripening time of spinning dope (in days), with the same polymer concentration of spinning dope, changes from 1 to 8, and the i‐value of the spinning dope increased with an increasing of the ripening time. At the ripening time of 8 days, tensile strength, elongation, and work of rupture showed minimum value attributed to the excessive degradation of the chitosan polymer chains left from the mixing operation that took place at the same time as the ripening time of the spinning dope, which means that the optimum ripening time of the spinning dope is 1 to 7 days. However, the thermal decomposition temperature and the onset of the exothermic temperature of thermal properties decreased with an increased ripening time. On the other hand, tenacity, elongation, and toughness decreased with increasing ripening time, and these qualities radically decreased with an increasing ripening time of more than a week. This indicates that the dispersion of aggregates and the degradation of chitosan polymer chains left from the mixing operation occurred at the same time during the ripening time of the spinning dope. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2870–2877, 2003