微尺度效应下的聚合物熔体粘度理论及试验

Theoretical and Experimental Approach of the Viscosity of Polymer Melt under Micro-scale Effect

根据毛细管流变仪测量原理,提出关于微尺度效应对聚合物熔体粘度变化的作用机理。基于Kelvin-Voigt本构方程,建立微尺度粘度模型。研制直径分别为1000μm,500μm,355μm毛细管口模,用PP,PS,HDPE材料进行不同剪切速率下的粘度试验研究。结果表明,同一剪切速率下,熔体粘度随口模直径的减小而降低;随着剪切速率的增加,粘度减小趋势在缩小。将试验相关数据代入微尺度粘度模型进行理论计算,结果表明理论曲线与试验曲线相符合,最大误差小于8%,验证数学模型的合理性,这对微注塑成型和微挤出成型,精确模拟充模流动和指导微模具设计有重要理论参考价值。

The mechanism of micro-scale effect contributing to the change of polymer melt viscosity is proposed on the basis of the measurement principle of capillary rheometer.Based on Kelvin-Voigt constitutive equation,a mathematical model of micro-scale viscosity is built.The micro channel dies of 1 000μm,500 μm and 355 μm diameter are developed and with several polymers,including PP,PS and HDPE,the measurement experiments of polymer melt viscosity are carried out at various shear rate.The results show that the melt viscosity reduces with the decrease of micro-channel size at the same shear rate and that the difference of viscosities in different micro channels reduces with the increase of shear rate.Test data are incorporated into the mathematical model for theoretical calculation.Results show that theoretical curves are consistent with experimental curves and the maximum difference is less than 8%,which verifies the rationality of the mathematical model.This finding provides the theoretical and experimental references for accurate simulation of filling flow and design of micro mold in micro injection molding and micro extrusion.