中文摘要：

应用共转导数型本构方程研究了液晶高分子纺丝挤出过程的拉伸黏度，应用计算机符号运算软件Maple得出解析表达式，拉伸黏度与拉伸率之间关系（随剪切速率变化）表明存在分岔现象，得出拉伸黏度显著高于相应的剪切黏度，解释了液晶高分子熔体挤出时不发生挤出胀大的物理机制。

英文摘要：

Using the constitutive equaiton of co-rotational derivative type for LC polymer melt, the extrusion process of LC polymer melt is investigated. The extrusion process near the die exit of the fiber spinning is represented by a viscometric-extensional flow. Using the computational symbolic manipulation software Maple, analytical expressions of the elongational viscosity are derived. The relationship between elongational viscosity and extension rate under varying shear rate shows bifurcation behaviour and considerable increase of elongational viscosity, when the orientational motion of the director vector is considered. The contraction of extrudate is caused by the high elongational viscosity for LC polymer melt, which is a rheological explanation of anti-die swell of LC polymer melt in extrusion process.