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聚合物的实际成型加工过程中,熔体在充填过程中不仅要受到热历史的作用,而且要受到剪切应力的作用,所以就不可避免地发生流动诱导结晶及取向现象。本文基于悬浮液理论和分子动力学方法,建立聚合物流动诱导结晶取向的数学模型,研究了剪切作用对结晶聚合物流动诱导结晶取向的影响。模型将结晶体系假设为结晶晶粒分散于无定型基质的悬浮液,通过取向张量计算取向因子,预测剪切过程中的晶相的取向行为。使用谱方法离散求解扩散方程,并计算取向分布函数和取向张量,模拟和分析了简单剪切场下结晶聚合物的流动诱导结晶取向行为。模拟结果表明,剪切强度对聚合物熔体的取向行为有着显著的影响,较高的剪切速率有助于晶区较早的完善取向。
In the actual molding process of polymers, the melt is not only subjected to thermal history but also subjected to shear stress in the filling process, so that the flow-induced crystallization and orientation inevitably occur. Based on the theory of suspension and molecular dynamics, a mathematical model of polymer-induced crystallization orientation was established and the effect of shear on the crystal-orientation of crystalline polymer was also studied. In the model, the crystal system is assumed to be a suspension of crystal grains dispersed in an amorphous matrix. The orientation factor is calculated by the orientation tensor to predict the orientation behavior of the crystal phase during the shearing. Diffusion equations were discretized using the spectral method, and the orientation distribution function and orientation tensor were calculated. The flow-induced crystal orientation behavior of the crystalline polymer under a simple shear field was simulated and analyzed. The simulation results show that the shear strength has a significant effect on the orientation behavior of the polymer melt, and the higher shear rate contributes to the earlier perfect orientation of the crystalline zone.