聚酯熔体在喷丝孔中剪切流动对纺丝动力学的影响

Effect of shear flow of polyester melt in spinneret hole on spinning dynamics

通过建立动力学模型,采用有限元的方法研究了喷丝孔结构对涤纶熔纺动力学的影响;通过改变喷丝孔微孔直径、增加微孔出口倒角,计算得到了喷丝孔内熔体的挤出速度和压力分布,以及纺程段丝条的速度、速度梯度、直径、温度、拉伸应力、取向和结晶分布;进一步讨论了微孔直径和微孔出口倒角对于喷丝孔内熔体的流动行为、压力降、挤出胀大以及纺程段丝条的结构性能的影响。结果表明:改变喷丝孔微孔直径能够有效地调控喷丝孔内熔体的挤出速度和压力降,从而改变挤出胀大比和拉伸应力;微孔出口倒角对喷丝孔内熔体流动影响不大,主要影响纺程段丝条的结构与性能;喷丝孔微孔带有出口倒角时,可以削弱纺丝过程的挤出胀大现象,纺程段丝条的拉伸应力、取向度和结晶度都有不同程度的提高,并且会使发生取向和结晶的位置更加靠近喷丝板。

The effect of the spinneret hole structure on the melt spinning dynamics of polyester fiber was studied through dynam- ic modelling and finite element analysis method. The melt extrusion rate and pressure distribution in the spinneret hole were cal- culated by changing the spinneret microhole diameter and increasing the outlet chamfer angle of the microhole, as were the yarn velocity, velocity gradient, diameter, temperature, tensile stress, orientation and crystalline distribution along the spinning line. The effects of the diameter and outlet chamfer angle of the microhole on the flow behavior, pressure drop and extrusion swell of the polyester melt in the spinneret hole and the structure and properties of the yarn along the spinning line were further discussed. The result showed that the extrusion rate and pressure drop of the polyester melt in spinneret hole could be efficiently adjusted by changing the spinneret hole diameter, cansing the extrusion swell ratio and tensile stress to change; the outlet chamfer of the mi- crohole did not have much effect on the melt flow in the spinneret hole, but affected the structure and properties of the yarn along the spinning line; the extrusion swell phenomenon could be depressed during the spinning process, the tensile stress, orientation degree and the crystallinity of the yarn could be increased in some degree along the spinning line, and the position where the ori- entation and crystallization occurred became closer to the spinneret when the spinneret microhole had the outlet chamfer.