医用塑料微管气辅挤出成型的理论与实验研究

Medical Plastic micro-tubes are widely used now days, for the problems caused by the die-swell, melt fracture and extrudate distortion to which often affect the product quality and manufacture efficiency in the production of plastic micro-tubes, the program is devoted to the plastic micro-tube extrusion study with the use of gas-assisted extrusion technology. The numerical simulation will be conducted through the set up of gas-assisted plastic micro-tube extrusion model with the consideration of the integrated affection between the micro scale effects and gas-liquid-gas multilayer flow, and the developing of the accordingly finite element methods; The experimental study will be carried out by building the experimental set-up through developing gas-assisted extrusion die of plastic micro-tube and gas-assisted gas control system; With the results of experiments and numerical simulation, the distribution of various fields and the influence of gas layers and their mutual affection on the extrudates will be analysed, and the relation between the gas flow states, materials rheological properties, process parameters , die structure and the distribution on the fields in and out of die, die swell, melt layer appearances will be revealed. The influencing factors and mechanism of gas-layer stability will be approached. On the above basis the process conditions of extrusion and optimization rules of extrusion die will be presented.

医用塑料微管应用日益广泛，针对生产中存在的挤出胀大、熔体破裂和扭曲变形等影响挤出质量和速度的难题，项目拟将气辅挤出成型技术应用于塑料微管挤出成型而展开研究，通过建立考虑微尺度因素和气-液-气多相分层流动耦合作用的塑料微管气辅挤出成型机理模型及发展相适应的有限元算法，对成型过程进行数值模拟；通过研制塑料微管气辅挤出口模和完善气辅控制系统构建塑料微管气辅挤出实验平台，在此基础上开展实验研究；通过对数值模拟和实验结果的分析，研究塑料微管气辅挤出成型过程中各场量的分布、气垫膜层以及它们相互作用对挤出结果的影响规律，揭示气体流动状态、熔体流变性能、工艺参数、口模构型对塑料微管气辅挤出口模内外各场量、挤出胀大、料层界面形貌的影响规律，探索形成稳定气垫膜层的条件，探明影响气垫膜层稳定性的因素和影响机理，在此基础上提出塑料微管气辅挤出成型的工艺条件和塑料微管气辅挤出口模设计的优化原则。

冠状动脉导管、造影导管和导尿管等医用塑料微管在临床治疗中的应用日益广泛。随着加工技术的改进，精密挤出技术广泛的应用于医用塑料微管的连续加工。然而，在塑料微管挤出过程中易出现挤出胀大、熔体破裂和扭曲变形等现象，限制了加工效率和生产成本。塑料微管挤出成型过程引入气辅技术可使口模内熔体由黏着流动转变为滑移流动，可以减小口模中熔体的剪切应力，从而有效地消除挤出胀大、扭曲变形的问题。因此，为了探明气辅挤出成型技术在医用塑料微管挤出过程的作用机理，优化加工工艺，本项目开展了以下研究：建立了考虑腔内气垫层气体流动的塑料微管气辅挤出模型，对成型过程进行数值模拟，得到了内气垫层气体的流动对微管的挤出成型造成影响规律；建立了考虑熔体可压缩性的内外双气辅挤出模型，研究了熔体可压缩性对熔体流变性能和挤出成型的影响规律。通过数值模拟方法对塑料微管气辅挤出口模进行了优化设计和加工制造，搭建了双气辅挤出医用塑料微管实验平台。通过挤出实验和数值模拟研究，揭示了影响气垫层稳定性的因素和影响机理，探明了气体参数、熔体流变性能、工艺参数、口模结构参数对口模内熔体各场量、挤出胀大、微管尺寸的影响规律。