铸膜液流体力学特性与膜形态结构

HYDRODYNAMIC CHARACTERISTICS OF FILM CASTING TO FORM MEMBRANE AND MEMBRANE MORPHOLOGY

通过对铸膜液的流体力学稳定性分析和计算机模拟,研究了与铸膜液流体力学特性相关的膜形态结构,结果表明流体力学不稳定性会导致膜面周期性地出现凹凸不平、聚集体和孔洞等结构。还探讨了过量分子作用势梯度、重力、粘度和表面张力等因素对这些形态结构的影响及消除这些不良结构的原则,用纹影仪观察了铸膜液的蒸发过程,证实铸膜液蒸发过程中出现流体力学不稳定性所致的不均匀结构和对流结构。用光学显微镜和电子显微镜观测了成膜后的形态结构,验证了理论分析结果。

On the basis of stability analysis of film casting to form membrane, membrane morphology related to hydrodynamic characteristics of the film was studied by computer simulation. It was pointed out that hydrodynamic instability can result in periodic tinevennesses, aggregates and holes on the membrane surface. The effects of excess intermolecular potential energy gradient, gravity, viscosity and surface tension op membrane structure, and the methods to eliminate these structures were discussed. The schlieren observation of the evaporation step of casting solutions was carried out. It was proved that nonhomogeneous and convective structure resulting from hydrodynamic instability would appear in the casting solution during evaporation. Unevennesses, aggregates and holes on the mumbrane surface were observed by optical microscope ana SEM, which corroborated the results of the theoretical analysis.