【作者】 黄伟；

【导师】 吴大鸣；

【作者基本信息】 北京化工大学 ， 机械设计及理论， 2008， 硕士

【摘要】 双腔医用导管是一类特殊的中空异型管材,具有截面尺寸小、内腔形状不规则、壁厚不均匀的特点,对成型设备与工艺要求严格,与传统的管材挤出存在较大差异。本文研制出精确气体流量控制系统并将其引入挤出过程,向双腔注入恒流量气体辅助熔融态PA12挤出成型,是一种新颖的导管成型工艺。为得到较好的导管截面形状,本文从材料的流变特性、机头设计、注气流量的控制以及挤出工艺参数的调节四个方面进行了实验研究,得出的结论对双腔导管的挤出成型有一定的参考作用。导管挤出过程中,熔体粘度的影响显著。本文首先对PA12材料特性进行了毛细管流变测试,分析了粘度与温度、剪切速率之间的关系,为挤出温度的控制提供了重要的参考依据。基于气体辅助成型的机头口模、芯棒、注气孔和对中调节设计,是本文的一大特色。本课题重点研究不同气体流量下的高聚物熔体壁的变形情况,并用挠度对这种变形趋势进行表征。挠度用二次抛物线进行了拟合,较好的反映了实验结果,并探讨了抛物线二次项系数的变化规律,同时还建立了熔体壁厚与注气流量之间的关系。针对双腔医用导管的不规则截面,提出了椭圆度和壁厚均匀度两个截面形状表征参数,并研究了机头温度、螺杆转速、牵引速率和注气流量对两个表征参数的影响,优化了挤出工艺参数。为满足医用要求,最后对医用导管的双腔流速进行了实验测量和理论计算。更多还原

【Abstract】 Double lumen medical catheter is a kind of special hollow profile tube with small cross-section, irregular shape of inner lumen and non-uniform wall thickness, which is strict to extrusion equipments and processing. It differs from traditional tube extrusion processing.In this dissertation, gas flow controller system was designed.In extrusion process, precision gas flow controller system injects constant flow gas to double lumen of PA12 melt to assist molding, which is an innovation point of the dissertation. It is also a new-style extrusion processing of catheters. In order to obtain good cross-section shape of catheter, PA12 rheologic behavior, die design, gas flow and extrusion processing parameters were studied on the basis of experiments. The conclusions will guide extrusion processing of medical catheters.Melt viscosity has significant influence on extrusion of catheters. Firstly, PA12 was tested by capillary rheometer. The relationship among viscosity, temperature and shear rate was established, which provide important reference for temperature control during catheter extrusion. The design of dies, mandrel, gas hole and Centering adjustment based on gas-assisted molding is a big feature.The key study is the deformation of polymer melt wall at different gas flow in this dissertation, which was attributed by deflection curve. The results showed that deflection curve of PA12 melt conformed to second-degree parabola. Moreover, the changing rules of second-degree coefficient were discussed and the relationship between melt wall thickness and gas flow was found. To attribute medical catheter’s cross-section shape, ellipticity and wall thickness uniformity were presented. The factors which influenced shape of catheter cross-section, including die temperature, screw rotational speed, tractive rate and the gas flow were analyzed, which made processing parameters optimized. At last, flow velocity of double lumen was measured experimentally and computed theoretically.更多还原