不同口模直径下聚合物熔体流变特性试验研究

Experimental study of rheological characteristics of polymer melts under various die diameters

采用双料筒毛细管流变仪,研究了口模直径从1.5 mm减小到0.5 mm时聚苯乙烯(PS)、聚甲基丙烯酸甲酯(PMMA)、聚丙烯(PP)和高密度聚乙烯(HDPE)4种聚合物熔体的流变特性,并讨论了在口模直径为0.5 mm条件下温度对熔体剪切粘度、温度和剪切速率对熔体非牛顿指数的影响.试验结果表明,在剪切速率102～104s-1,4种聚合物熔体的剪切粘度均随剪切速率的提高而减小.PS和PMMA熔体的剪切粘度随着口模直径的减小而增大,PP和HDPE熔体的剪切粘度随着口模直径的减小而减小.随着剪切速率的提高,不同口模直径下熔体剪切粘度的差异逐渐缩小.在口模直径为0.5 mm的条件下,4种聚合物熔体的剪切粘度对温度的依赖性符合Arrhenius方程;熔体的非牛顿指数随着温度的升高而增大,随着剪切速率的提高而减小.

The rheological characteristics of four polymer melts polystyrene （PS）, poly （methyl methacrylate） （PMMA）, polypropylene （PP） and high density polyethylene （HDPE） were investigated using a double capillary rheometer under the die diameter from 1.5 mm to 0.5 mm. The effects of temperature on shear viscosity and the effects of temperature and shear rate on non-Newton exponent of melts were discussed when the die diameter was 0.5 mm. The results show that the shear viscosity of four polymer melts decreases with the increase of shear rate at 10^2-10^4 s^-1. The shear viscosity of PS and PMMA increase8 with the decrease of die diameter, but that of PP and HDPE decreases with the decrease of die diameter, and small differences of shear viscosity under various die diameters are observed with the increase of shear rate. When the die diameter is 0.5 mm,Arrhenius equation is found to be suitable to describe the relations between shear viscosity and temperature for four polymer melts. The non-Newton exponent of four polymer melts increases with the increase of temperature and decreases with the increase of shear rate.