| Summary: | 碩士 === 國立臺北科技大學 === 化學工程研究所 === 95 === In recent years, the textile industry puts more and more investments on the research and design of functional fibers, such as profiled fibers, conjugated fibers and hollow fibers. However, there are some difficulties in the manufacturing of conjugated hollow fibers, possessing two or more kinds of fiber characteristics. In order to increase the successful chance of developing products, we chose two kinds of the die geometry, such as 4-T typed spinneret and sheath/core spinneret, to simulate the flow behavior of conjugated molten polymers co-extruding from the spinneret, and to find the key factors of forming fibers.
First, Nylon, PET, or CO-PET with hydrophilic function is the sheath layer material and a series of hydrophobic PP are respectively arranged as the core material. The rheological data of materials used in the study are measured by the parallel plate rheometer and the capillary rheometer. For the parts of computer simulation, we utilized the numerical approach of finite element method with optimesh-3D re-meshing to solve a free surface problem. The numerical algorithms used in the computations include Newtonian iteration, Picard iteration and EVSS/SU. To study viscosity, shear thinning and elasticity effects on the spinning behavior of the conjugated hollow fiber, four appropriate constitutive equations, for instance, Newtonian fluid, Cross model, Maxwell model and PTT model, are adopted in our simulations.
We find that the gluing is the key factor on forming fiber. Moreover, not only the die swell but also the deflection of molten streams is demonstrated to be the major factors, affecting the gluing process. For the polymer stream deflection, flow rate ratio, viscosity ratio and elasticity ratio are proved to be the controlling factors. From these factors, the operating windows are found to lessen the extent of deflection. In addition, we also confirm that the elasticity can influence the die swellings. Finally, the simulation results are compared with experimental data.
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