气辅技术对聚合物棒材微共挤成型的影响

Influence of Gas-A ssisted Technology on Polymer Micro Co-Extrusion Molding

将气体辅助技术应用于聚合物棒材微共挤成型中,建立了棒材微共挤流动三维数值模型,运用有限元方法进行了模拟研究,对比分析了在聚合物传统和气辅微共挤成型过程中,速度场和剪切速率的分布情况,及由此引起的挤出胀大率的变化,同时,分析了传统和气辅微共挤口模内熔体压降曲线的差异。研究结果表明,在聚合物传统微共挤过程中,仍存在挤出胀大、速度场分布不均、口模压降较大等问题。在气辅微共挤过程中,由于气垫层的润滑作用,口模内熔体压力降接近零值,口模出口端面熔体速度场均匀一致、剪切速率接近零值,即气体辅助技术能够有效消除微共挤过程中的挤出胀大、熔体破裂和变形等问题,能大幅提高微挤出复合制品质量。

The gas-assisted technology was applied in the polymer micro co-extrusion molding. The three-dimensional numerical flow models of polymer micro co-extrusion process were established,and the numerical simulation study was carried out by the finite element method. The die swell rate,velocity distribution,shear rate distribution and melt pressure drop curve in polymer traditional/gas-assisted micro co-extrusion molding in details were discussed. The research results showed that there were still some problems,such as die swell,nonuniform velocity field and large die pressure drop,in the traditional micro coextrusion process. However,there were uniform velocity field and the shear rate was close to zero at the die exit plane for the lubrication effect of the gas layer in the gas-assisted micro co-extrusion molding. And the melt pressure drop approximated to zero within the die. So the gas-assisted technology was greatly conducive to the improvement of micro composite products quality by eliminating the die swell,melt rupture,deformation and so on.