基于PTT黏弹本构模型的聚合物气辅微共挤成型研究

Research on polymer gas-assisted microcoextrusion moldingbased on PTT viscoelastic constitutive model

基于PTT黏弹本构模型,构建了描述棒材包覆双层微共挤黏弹流动行为的三维数值模型,采用Elastic Viscous Split Stress、Evolution等方法实现了有限元数值计算,通过分析传统/气辅微共挤的挤出胀大和熔体的速度、剪切速率和压力分布,探究了聚合物气辅微共挤的成型机理。结果表明,气辅微共挤成型过程中,由于气垫膜层的存在及其润滑作用,可有效消除熔体的二次流动且不存在明显剪切速率和口模压降,使熔体沿挤出方向速度分布均匀。

The three-dimensional numerical model describing the viscoelastic flow behavior in the micro channel was founded based on PTT constitutive model.The numerical calculation was realized by using the finite element methods.The polymer gas-assisted micro coextrusion molding mechanism was explored by analyzing the melts’die swell,velocity,shear rate and pressure distribution in traditional/gas assisted micro coextrusion.The research results show that,in gas-assisted micro coextrusion process,the melts’secondary flow,shear rate and die pressure drop can be effectively eliminated due to the lubrication of gas film between the melt surface and die wall.And the melts’velocity distribution along the extrusion direction can be steady.