【摘要】 以PP和PS两种聚合物为实验材料,使用截面为矩形、层比为1的双层共挤口模,实验研究了聚合物共挤成型过程中的挤出胀大现象.采用Phan-ThienandTanner(PTT)本构方程,建立了复合共挤口模内外熔体流动的三维黏弹数值模型,有限元模拟了共挤出的胀大过程,计算分析了熔体在口模内外的速度场及剪切速率分布.研究表明,在入口体积流量相同的情况下,两熔体挤出口模后,存在由黏度较低的PP向黏度较高的PS一侧偏转的现象,型材截面呈不对称畸变.数值模拟结果与实验结果较吻合,两种聚合物熔体的速度分布决定了共挤出胀大过程中熔体的偏转流动行为,口模出口处的剪切速率分布基本决定了挤出胀大后型材的截面形状.更多还原

【Abstract】 The extrudate swell in polymer bicomponent coextrusion process had been investigated via experiment and numerical simulation.For the study,PP and PS were extruded side by side through a double-layer(layer ratio=1) rectangular coextrusion channel.The three-dimensional flow of the viscoelastic melts inside and outside the die was modeled with Phan-Thien and Tanner constitutive equation,and then a finite element simulation on the co-exturdate swell was performed.The velocity and shear rate distribution were calculated and analyzed.The study showed that,as their inlet volume flow rates were kept same,there was a deflexion from PP to PS(with higher viscosity) outside the die,and the cross-section of the profile presented an asymmetrical distortion.The simulated results were in accordance with the experimental results. Velocity distribution of the polymer melts determines the deflexion,and the cross-section shape depends on the shear rate distribution at coextrusion die exit.更多还原