聚苯乙烯共混体系发泡过程中气泡壁不均匀性的实验与模拟

Experimental and Simulation of Inhomogeneity of Bubble Wall in Foaming of Polystyrene Blends

将2种不同相对分子质量的聚苯乙烯(PS)共混,并采用超临界CO_(2)间歇发泡工艺制备其发泡材料。采用高倍扫描电镜实验测量PS共混体系发泡后气泡壁的形状参数,即气泡壁厚度分布δ_(θ)/δ_(max),同时基于气泡壁形状演变模型(BWSE)模拟计算对应样品发泡过程中的δ_(θ)/δ_(max),将模拟结果与实验值进行对比,发现模拟所得δ_(θ)/δ_(max)曲线与实验所测结果具有相同趋势。在多种比例共混的PS体系中,模型预测的气泡壁非均匀因子(γ)与实验值呈现良好的相关性和一致性,表明BWSE模型能用于半定量化分析不同PS在泡孔生长过程中的微观气泡壁形状和泡孔结构。模拟结果揭示了PS流变行为与其发泡材料微观泡孔结构的内在关联:流变性能影响PS的气泡壁不均匀拉伸行为,通过BWSE模型能够基于流变性能数据计算出泡孔壁的变形规律。

The polystyrene(PS)blends with different molecular weight were prepared by melting extrusion.The batch foaming process of the PS blends was carried out with supercritical CO_(2).The shape parameter,δ_(θ)/δ_(max),depicting geometrical inhomogeneity of bubble walls of the PS blends was simulated by the bubble wall shape evolution model(BWSE).The experimental values of shape parameter of the bubble walls were characterized by SEM at high magnifications.Comparing the experimental results and model predictions,it is shown that the two types of curves have the similar decline trend.With the change of PS blending ratio,the experimental values and model predictions of heterogeneity factorγpresent good correlation and consistency.The result indicates that the BWSE model can be applied to semi-quantitatively analyze the microscopic bubble wall shape and bubble structure of different PS during bubble growth,and the simulation results reveal the intrinsic correlation between the rheological behavior of PS melt and microscopic structure of the final PS foams.The correlation is that rheological properties of PS affect the inhomogeneous stretching behavior of the bubble walls,and then the deformation degree of the bubble walls can be calculated based on rheological data through the BWSE model.