聚苯乙烯微孔发泡中气泡长大及冷却定型模拟

本文以聚苯乙烯（PS）-超临界CO₂系统为例，提出了一种基于细胞模型，结合动量方程、质量方程、扩散方程及本构方程建立气泡长大及冷却定型问题的数学模型。用MATLAB编制了基于以上数学模型的仿真模拟程序。在模拟过程中，通过引入材料性质与温度、压力、CO₂浓度的关系式，确定了工艺参数和微孔形态之间的量化关系。结果表明，三个工艺参数对PS-CO₂气泡长大的影响：CO₂浓度 > 压力 > 温度。由正交模拟实验可知，不同加工条件下得到的气泡半径最大为49.5 μm，最小为1.27 μm，其中适于微孔发泡的气泡半径则处于10~25 μm之间。另外通过对气泡冷却定型的研究得到，快速冷却可以使气泡密度增加、气泡尺寸减小。

Numerical simulation of bubble growth and solidification in microcellular foamed polystyrene

In this paper, a polystyrene (PS)-supercritical CO₂ system was used herein as a case example to simulate bubble growth behavior and cooling and solidification. The mathematical model based on the cell model was established to solve momentum equation, mass equation and diffusion equation. The software program of system simulation based on the above mathematical model was compiled with MATLAB language. In the process of simulation, the quantitative relationship between process parameters and microcellular morphology was determined by introducing the relationship between the material properties and the temperature, pressure and CO₂ concentration. The results show that CO₂ concentration has the greatest effect on bubble growth, and the effect of temperature is the least for the PS-CO₂ system. According to the simulation of orthogonal, under different processing conditions, the maximum value of bubble radius is 49.5 μm, the minimum value is 1.27 μm, and the suitable bubble radius for microcellular foaming is between 10 μm and 25 μm. In addition, the study of the bubble cooling shows that the increase of cooling rate will increase the bubble density and reduce the bubble size.