塑料微管气辅挤出成型机理、影响规律及工艺优化调控研究

Plastic micro-tube has the huge application prospects and high economic values, which has been widely used into some fields, such as medical interventional diagnosis, optical fiber communication, automobile oil circuit, precision instrument, etc. In this project, in order to solve the problems including the extrudate swell, melt fracture, and extrudate distortion existed in the plastic micro-tube traditional extrusion, the gas-assisted technique was applied into the plastic micro-tube extrusion forming. The basic method is given as follows: establishing the double gas layers at the melt/die’s inner wall interface and the melt/mandrel’s outer wall interface to decrease the shear and tensile stresses of melt at the both walls, which leads to overcome the above mentioned three problems of traditional plastic micro-tube extrusion forming. In order to improve the novel technique of plastic micro-tube gas-assisted extrusion forming, the following several key problems of plastic micro-tube gas-assisted extrusion forming should be mainly theoretically and experimentally studied in this project, such as, mechanism innovation of the plastic micro-tube gas-assisted extrusion forming, the mechanism of “melt/gas”interface change, influence and mechanism of micro-scale effects, optimal design of the gas-assisted extrusion die, the influence mechanism and law investigation of melt’s physical property parameters, process parameters, and die’s structures. At the same time, to optimize and regulate the process parameters of gas and melt. Based on the studies of these above mentioned problems, the main aims of this project are to ascertain the mechanisms and influence laws of plastic micro-tube gas-assisted extrusion forming, and to attain the optimal process parameters of gas layers and melt. Finally, to provide the technical guidances for the practical manufacture of plastic micro-tube gas-assisted extrusion forming technology.

塑料微管在医学介入诊疗、光纤通信、汽车油路和精密仪器等领域，具有广阔的应用前景和较高的经济价值。本项目为了解决塑料微管传统挤出中存在的“挤出胀大”、“熔体破裂”和“扭曲变形”等问题，将气辅技术应用于塑料微管挤出中，通过在微管熔体与口模内壁面和芯棒外壁面之间形成内外双层气垫膜层，来减小熔体与壁面之间的剪切和拉伸等应力，从而克服传统塑料微管挤出存在的上述三大问题。为了有助于塑料微管气辅挤出这项新技术的发展，本项目拟对塑料微管气辅挤出中的几个关键性问题进行理论和实验研究，包括：塑料微管气辅挤出成型机理创新、“熔体/气体”界面变化机理、微尺度效应的影响及机理、气辅挤出口模的优化设计，以及熔体物性、工艺参数和口模结构的影响机理和规律，并对工艺参数进行优化调控。通过上述问题的研究，来揭示塑料微管气辅挤出成型机理、影响规律，并找到最优的熔体和气体工艺参数，为塑料微管气辅挤出成型技术走向实际生产提供指导。

塑料微管在医学介入诊疗、光纤通信、汽车油路和精密仪器等领域，具有非常广阔的应用前景和较高的科学和经济价值。在塑料微管挤出过程中，由于熔体在挤出机和口模流道内经历较大的剪切和拉伸，在较大的剪切应力和弹性应力，使得熔体分子产生了较大的弹性储能，在挤出口模出口处，会容易产生挤出胀大、挤出变形和熔体破裂等问题。本项目为了解决塑料微管传统挤出中存在的“挤出胀大”、“熔体破裂”和“扭曲变形”等问题，将气辅技术创造性地应用于塑料微管挤出中，通过精密设计气辅装置和气辅挤出口模，在微管熔体与口模内壁面和芯棒外壁面之间形成稳定的内外双层气垫膜层，来减小熔体与壁面之间的剪切和拉伸等应力，从而克服传统塑料微管挤出存在的上述三大问题。为了有助于塑料微管气辅挤出这项新技术的发展，本项目针对塑料微管气辅挤出中存在的几个关键性问题进行了理论和实验研究，包括：塑料微管气辅挤出成型机理创新，通过构建了“气-液-气”多相流几何模型来通过有限元数值模拟方法探究塑料微管气辅挤出成型机理；在构建的新型模型基础上，深入地探究了“熔体相与内外气体相”耦合作用对彼此的影响，并且针对气液耦合效应对“熔体/气体”界面变化机理进行了深入研究；并且针对若干种微尺度效应（黏度尺度效应、熔体可压缩效应、气体可压缩效应、滑移效应、表面张力效应和黏性耗散效应等）对塑料微管气辅挤出成型的影响及机理进行了研究；并且，利用逆向有限元数值模拟方法结合正向正交实验方法，对塑料微管气辅挤出口模进行了优化设计；并对熔体物性、工艺参数和口模结构的影响机理和规律进行了有限元数值模拟。通过采用有限元数值模拟和实验的研究，深入地揭示了塑料微管气辅挤出成型机理、工艺参数影响及规律，并通过对聚丙烯熔体气辅挤出实验，找到了最优的熔体和气体工艺参数，为塑料微管气辅挤出成型技术走向实际生产提供指导。