- 學位論文
熔噴在立體不織布製作上之應用
Manufacturing of Three-dimensional Non-woven Fabrics by Melt-blown Process
摘要
熔噴技術生產的纖維很細，同時熔噴布比表面積大、空隙小而空隙率大，故其過濾性、屏蔽性、絕熱性和吸油性等應用特性是用其它方法生產的不織布所難以比擬的。 熔噴法不織布的製造技術，是將高分子聚合物通過螺桿擠出機擠壓成熔融態，再由高壓熱空氣拉伸成超細纖維噴塗在立體物件上形成立體不織布。過去的熔噴技術是用來製作二維的不織布，本研究是針對熔噴製作三維立體不織布作數值模擬及實驗印證。由於高速空氣慣性力大、纖維質地輕，故纖維的流動路徑可用空氣流動路徑來表示。本研究採用有限體積法，使用穩態與非穩態紊流模式，搭配多參考座標系模型、滑移網格模型與動網格模型，來探討在立體模具周圍所產生的高速空氣流場。 模擬結果顯示，物體為不規則形狀，導致各切面的邊界層分離效果不同，在鈍形物體後方產生不同的渦流。在熔噴過程中，未包覆在物體上的纖維越過了物體，在物體後方因渦流的產生使得纖維發生纏繞現象，小而影響物體包覆效果，大而影響實驗無法順利進行；為了使實驗順利，必須解決因邊界層分離而產生的渦流，在不能改變物體的條件下，故只能加以外力解決纖維在渦流處產生的纏繞現象，並經由實驗數據印證，希望藉此能有助於產業界對此製程的開發。
並列摘要
Melt-blown fabrics are lightweight with a high surface area, small void and high porosity. Hence they have better filtration, shielding, insulation, oil absorption, etc than nonwoven fabrics by other manufacturing technologies. In meltblowing, molten polymer is extruded through many orifices in spinnerets. The molten polymer is jacketed on both sides by high speed air stream and elongated by the air-drag force to form fibers, which are collected on a drum or other suitable collection surface. In the past, researches use meltblowing technique to analyze manufacturing technique of 2D nonwoven sheet. This thesis numerically and experimetnally investigates manufacturing technique of 3D nonwoven structures, and seek for it’s possible application. Because high inertia force of high speed air and lightweight fiber, the flow path of fibers is the air flow path. Finite volume method is used to simulate steady-state and unsteady-state turbulence models with moving reference frame model, sliding mesh model and dynamic mesh model. The results of simulation show that the irregular objects lead to different boundary layer separation in each cross section of the object, and produce different vortex strength. In the simulation of meltblowing process, it demnostrates that some fibers may flow over the obtuse section and circulate behind it. From observation of experiments it is found that the fibers may get entangled, and interfere the melt-blown process. In order to make the 3-D non-woven structure manufacturing successful, it is believed simulation and experiment data analysis in this study can provide some important technique reference to the 3-D non-woven industry.