【摘要】 采用Phan-Thien-Tanner(PTT)本构方程描述聚合物熔体共挤分层流动的黏弹行为,建立了C形双层气辅共挤非等温流动理论模型,并数值实现,研究了熔体入口体积流率对挤出胀大率和第二法向应力差的影响,同时分析了熔体挤出胀大率与第二法向应力差之间的规律性联系。研究结果表明,当两熔体流率不相等时,单层熔体挤出胀大率随着自身流率的增大而增大,随着另一熔体流率的增大而减小,甚至出现负值;当两熔体流率相等时,单层熔体挤出胀大率不随流率的变化而变化;熔体整体挤出胀大率则不随流率的变化而变化,始终接近零值;熔体的挤出胀大率与第二法向应力差有关,且正比于第二法向应力差的绝对值。更多还原

【Abstract】 A 3D non-isothermal viscoelastic numerical model was found for a two-layer gas-assisted coextrusion through the C-profiled channel with PTT model describing the viscoelastic flow behavior of molten polymer and the simulation was carried out. The influence of melt inlet volumetric flow rate on die swell and secondary normal stress difference was researched and the relation between dying swell and secondary normal stress difference was investigated. The study results show that the melt swell ratio increases with its flow rate increasing and decreases with other melt flow rate increasing when two melts’ flow rate is not equal. The melt flow rate has little influence on melt swell ratio when two melts’ flow rate is equal. But the whole die swell ratio is always close to zero,whether the flow rate of the two melts is equal or not. In addition,the die swell ratio is proportional to the second normal stress difference in a gas-assisted coextrusion process.更多还原