多層膜共擠出製程的模內材料變形與流動行為探討

Abstract

多層膜共擠出製程是製作各種高品質的功能性塑膠膜的重要方法。本計畫擬針對多層膜共擠出製程中材料在模具內的變形與流動行為進行探討，以了解層間材料性質差異、成形條件、模具設計等對於多層膜製品品質的影響，並提供做為多層膜的膜層設計、各層材料的選擇與性質調整、模具設計、以及成形條件的決定等的參考依據。計畫分兩年來進行，茲分述如下。 第一年：首先進行由兩種材料構成的三層膜的共擠出實驗，觀察、量測合流後的材料變形流動行為。其次利用有限元素軟體POLYFLOW，並選用Bird-Carreau純黏性非牛頓模型，進行衣架形流路、合流部、以及合流部下游至模唇的三維流動分析。最後進行實驗結果與數值模擬結果的相互比較與檢證，期能了解各層材料的黏度與流速、合流角度、合流部間隙等因子對於合流後的材料變形流動的影響，並掌握材料在模具各階段流路內的變形與流動特性。 第二年：改為使用三種素材以進行材質非對稱的三層膜共擠出實驗，並增加對合流部下游的寬度面進行高速攝影，以觀察層間界面不穩定現象的發生過程。數值模擬的部分，改用White-Metzner黏彈性模型進行三維流動分析，並分別與實驗結果、第一年的純黏性數值模擬結果做比較，以進一步了解材料的黏彈特性對共擠出的變形流動的影響，以及對模內各階段流路使用黏彈性模型模擬的必要性。

The co-extrusion process of multi-layer film is an important approach to functional polymer films of high quality. This project will investigate the mold flow phenomena in the multi-layer co-extrusion process to understand the effects of material property differences between two contiguous layers, process conditions, and mold design, on the quality of produced multi-layer films. The results of this project will be useful for layer design of multi-layer film, mold design, and decision making for co-extrusion conditions. The project will be carried out for two years. In the first year, we will conduct co-extrusion experiments of two-kind-polymer three-layer film. The side view of the flow phenomena at the confluence will be recorded using a high speed camera. We will also perform three-dimensional analysis of the flow inside the coat hanger manifold, the confluence, and the downstream from the confluence to the die lip. This work will employ POLYFLOW, a finite element analysis software, and will select the Bird-Carreau model, a non-Newtonian viscous model, to use in numerical simulation. According to these results, we can figure out the effects of viscosity and velocity of each polymer layer, the converge angle, and confluence clearance on the flow phenomena at the confluence. Moreover, we can know the flow phenomena inside each section of the channel in the mold. In the second year, we will conduct co-extrusion experiments of three-kind-polymer three-layer film instead of two-kind-polymer three-layer film. In addition to the side view of the flow at confluence, the front view (film width plane) of the polymer flow at the downstream from confluence will be photographed using a high speed camera, so we can analyze the process of the unstable polymer interface. We will use the viscoelastic White-Metzner model to conduct three-dimensional numerical simulation of the mold flow. The results of viscoelastic numerical simulation will be compared to the experiment results, and the results of non-Newtonian viscous numerical simulation, respectively, to further understand the effect of the polymer viscoelastic property on the co-extrusion flow. The study will discuss the necessity of using a viscoelastic model in the numerical simulation of polymer flow inside each section of the channel in the mold.