Effect of oscillatory shear on polystyrene cell morphology

In the present study, a novel microcellular processing experimental setup is developed. With this setup, an oscillatory shear flow is superimposed perpendicular to a steady shear flow during microcellular processing. The effects of processing conditions such as processing pressure, shear rate, and vibration frequency on polystyrene (PS) cell morphology are investigated. The cell morphology is analyzed with a scanning electron microscope (SEM). The results show that the cell density increases and cell size decreases with the increase of processing pressure, shear rate, and vibration frequency. The effects of steady and oscillatory shear on PS cell morphology are further studied with lower melt flow index PS processed with a larger gap thickness. The results show that the final cell structure processed under simple steady shear flow shows an elongated oval shape, while those processed under combined shear flow show nearly spherical cell shape.