發(fā)布時間：2018-05-28 20:50

  本文選題：醫(yī)用級TPU + 微擠出　； 參考：《南昌航空大學》2017年碩士論文

【摘要】：隨著近年來微電子系統(tǒng)(MEMS)的發(fā)展,工業(yè)產品的微型化、精密化、輕量化趨勢日漸明顯,傳統(tǒng)成型技術也對微成型方向提出了新的要求。聚合物材料因密度小、高比剛度和比強度、優(yōu)良的生物相容性等特性,從而逐漸成為微小工業(yè)產品的主要成型材料,特別是在醫(yī)用器材成型方面,例如醫(yī)療微管的成型過程就是微擠出的重要應用之一。但是產品微型化也帶來了來自因尺度變化而帶來的問題,在微細流道中聚合物熔體的流變行為發(fā)生許多改變,許多傳統(tǒng)尺度成型過程中上不需要考慮的因素如壁面滑移現(xiàn)象、表面張力等微尺度效應在微擠出成型中的作用不容忽視。而氣輔擠出作為一種滑移擠出技術,能有效解決微擠出過程中微尺度效應帶來的相關問題。為此,本文針對醫(yī)用級熱塑性聚氨酯的氣輔微擠出過程,做出如下研究:首先,對醫(yī)用級熱塑性聚氨酯的穩(wěn)態(tài)流變性能和動態(tài)流變性能進行了測試,得到的穩(wěn)態(tài)流變數(shù)據(jù)被用于擬合得到非等溫冪率方程本構方程,得到的動態(tài)流變數(shù)據(jù)被用于擬合得到PTT黏彈性本構方程,得到的方程能分別從純黏性模型和粘彈性模型角度描述熔融態(tài)的醫(yī)用級熱塑性聚氨酯在擠出過程中的流變行為,為氣輔微擠出的數(shù)值模擬分析過程提供了模型依據(jù)。以直徑1mm的圓形截面擠出物為研究對象,根據(jù)氣輔擠出機頭設計理論和經驗,設計了氣輔微擠出機頭結構并確定了相關參數(shù),結合表面張力模型和壁面滑移理論,建立了2D軸對稱模型用數(shù)值模擬方法對氣輔微擠出過程進行了模擬,對比了氣輔微擠出和無氣輔微擠出的成型過程,并分析了成型工藝條件(成型溫度、熔體流量、氣體壓力、氣輔流道直徑)對流動過程和成型結果的影響。最后,加工并安裝了設計出的氣輔微擠出機頭,并進行了氣輔微擠出和無氣輔微擠出的對比實驗,并逐項實驗了成型溫度、螺桿轉速、輔助氣體進氣壓力、氣輔流道直徑對氣輔微擠出過程的影響。實驗結果表明氣輔滑移被引入了微擠出過程之后,能有效減少機頭內的壓力降,并對擠出物表面質量有一定程度的改善;成型溫度、螺桿轉速、輔助氣體進氣壓力、氣輔流道直徑等成型工藝條件都對成型過程有較大影響;氣輔微擠出的工藝條件正交實驗表明,氣輔微擠出適宜的工藝條件區(qū)間較為狹窄,實現(xiàn)穩(wěn)定的氣輔微擠出過程較為困難,容易產生竹節(jié)型擠出物。
[Abstract]:With the development of microelectronic system (MEMS) in recent years, the trend of miniaturization, precision and lightweight of industrial products is becoming more and more obvious. Because of its small density, high specific stiffness, specific strength and excellent biocompatibility, polymer materials have gradually become the main molding materials of micro industrial products, especially in the field of medical equipment molding. For example, the molding process of medical microtubules is one of the important applications of microextrusion. However, the miniaturization of the product also brings problems caused by the change of scale. The rheological behavior of polymer melts in the microchannel has changed a lot, and many factors, such as wall slippage, are not considered in the traditional scale molding process. The effect of surface tension and other micro-scale effects on micro-extrusion can not be ignored. As a slip extrusion technique, gas-assisted extrusion can effectively solve the related problems caused by micro-scale effect in micro-extrusion process. Therefore, in this paper, the gas-assisted micro-extrusion process of medical thermoplastic polyurethane was studied as follows: firstly, the steady and dynamic rheological properties of medical thermoplastic polyurethane were tested. The obtained steady state rheological data were used to fit the constitutive equation of the nonisothermal power rate equation, and the obtained dynamic rheological data were used to fit the PTT viscoelastic constitutive equation. The obtained equations can describe the rheological behavior of medical thermoplastic polyurethane in melt state from the point of view of pure viscosity model and viscoelastic model respectively, and provide the model basis for the numerical simulation and analysis of gas-assisted micro-extrusion process. Based on the design theory and experience of gas-assisted extruder head, the structure of gas-assisted micro-extruder head is designed and the relevant parameters are determined. The surface tension model and wall slip theory are combined with the surface tension model. A 2D axisymmetric model was established to simulate the gas-assisted micro-extrusion process by numerical simulation. The molding processes of gas-assisted micro-extrusion and non-gas-assisted micro-extrusion were compared, and the molding process conditions (molding temperature, melt flow rate, gas pressure) were analyzed. The influence of the diameter of the gas-assisted flow channel on the flow process and molding results. Finally, the designed gas-assisted micro-extruder head was machined and installed, and the contrast experiments between gas-assisted micro-extrusion and non-gas-assisted micro-extrusion were carried out, and the molding temperature, screw speed and auxiliary gas inlet pressure were tested one by one. Influence of Gas-assisted Channel diameter on Gas-assisted Micro-extrusion process. The experimental results show that the gas-assisted slippage can effectively reduce the pressure drop in the die head and improve the surface quality of the extruder to some extent after the gas-assisted slip is introduced into the micro-extrusion process, and the molding temperature, screw speed, auxiliary gas inlet pressure, The orthogonal experiments show that the suitable technological conditions of gas-assisted micro-extrusion are relatively narrow, and the process conditions of gas-assisted micro-extrusion have great influence on the forming process, and the orthogonal experiments show that the suitable technological conditions of gas-assisted micro-extrusion are relatively narrow. It is difficult to realize stable gas-assisted micro-extrusion process and easy to produce bamboo-shaped extrusion.
【學位授予單位】：南昌航空大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ320.663

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本文編號：1948141