模头胀拉塑料管材取向成型的机理

Mechanism of Die-Drawing by Stretching the Inside-Pressurized Pipes

提出了胀拉模头拉伸取向方法 .从流变特点看 ,这个双向拉伸过程类似于拉吹过程 .对高密度聚乙烯 ( HDPE)管材试样的变形特点及其微观机理分析发现 ,未拉伸的管坯沿着拉伸方向依次经过以下变形区域 :压力和拉伸力协同作用区 (即与壁面接触的双向拉伸区 )、颈缩区和“均匀”拉伸区 .在样品受热恢复试验分析的基础上 ,提出了在熔点附近大幅度快速拉伸时 。

This paper proposed a novel way of die drawing orientation——stretching the inside pressurized pipes, in which the rheological properties and the microscopic motions are similar with those in stretch blow molding. The characteristics of the deformations and micro mechanisms in the production of oriented HDPE pipes were analyzed. The parison moves towards the die passing the following zones: the region of co function by pressure and pull, i.e. the biorientation with the forced deformation in contacting the wall; the necking down region and the ‘uniform’ drawing region. This kind of analysis is distinct from the conventional techniques——the assumption of pure viscous flow or pure elastic deformation. The analyses of the thermal properties and the deformation imply that the molding state is in viscoselastic plasticity when the process is rapidly under way with the large stretch ratio near the melting point of the polymer, which is the advance in research of the molding pipes and hollow articles.