Experimental and Simulation of Inhomogeneity of Bubble Wall in Foaming of Polystyrene Blends
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 CO2.The shape parameter,δθ/δmax,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 factor y present 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.
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