【摘要】 在挤出机上安装自行设计的毛细管口模,对PP,HDPE和PS熔体采用挤出物胀大法在较高剪切速率下测量第一法向应力差N₁,发现:由于N₁受胀大比B和剪切应力τ_W的双重影响,因此弹性测试比粘性测试所需的毛细管口模长径比要大;将挤出物胀大法与其他测量N₁的方法进行综合的分析比较,结果表明,挤出物胀大法所测N₁值比较合理,并可满足一般工程计算的要求。更多还原

【Abstract】 The method of extrudate swell is used to determine the first normal stress difference N₁ of polymer melts at high shear rates. It is found that a longer die than that used in viscosity measurements is required for the determination of N₁, since N₁ depends on both the swelling ratio and the shear stress. The N₁ results obtained from the method of extrudate swell are compared with the results obtained by other means. It is concluded that the N₁ results obtained from extrudate swell measurements are as good as anything else, and is certainly good enough for engineering purposes.更多还原