稳态和振荡剪切流动下聚合物共混反应体系演化的格子玻尔兹曼模拟

LATTICE BOLTZMANN SIMULATION OF THE CHEMICALLY REACTIVE MIXTURES UNDER SIMPLE AND OSCILLATORY SHEAR FLOW

采用A/B/S三元共混体系为模型体系,其中S由A和B通过可逆的化学反应生成并充当增容剂.我们采用自由能形式的格子玻尔兹曼模拟方法,考察了在稳态及振荡剪切流动下化学反应速率、剪切速率和振荡频率对体系形态结构演化的影响.模拟给出了增容剂平均密度和空间分布随时间的演化,结果表明增容剂S的生成能有效地降低分散相的尺寸,并且通过控制化学反应速率、剪切速率和振荡频率能够有效地调控增容剂在体系中的分布,从而为控制反应共混体系的形态结构提供帮助.

The block copolymer or graft copolymer formed by the in situ interface chemical reaction can be used as effective compatibilizer in the process of polymer blending materials. The structural evolution of an A/ B/S ternary mixture is investigated in which the A and B components can undergo a reversible chemical reaction to form S which may act as a compatibilizer. The free-energy Lattice Boltzmann simulation method （LBM） was adopted in this study.：!n this theoretical frame work, the chemical reaction terms can be incorporated into the second order parameter drift-diffusion equation via a specific forcing term. Using this method, the effect of chemical reaction rate, shear velocity and oscillatory frequency on the structure evolution was simulated. We results denoted tha provided the space distribution and the time evolution of compatibilizer S. The simulative t the component S can reduce the size of the dispersed phase greatly. Increasing the chemical reaction rate too much can lead the compatibilizer to form independent phase zone and not distribute in the interface. The high shear velocity and low oscillatory frequency got the phase structure to be stretched especially closed to the shear boundary. They are the crucial factors determining the structure evolution of blend mixture under shear flow. Finally, these results provide guidelines for controlling the morphology of this complex mixture.