Erosion and breakup of polymer drops under simple shear inhigh viscosity ratio systems

摘要

The deformation and breakup of a sinlge polycarbonate (PC) drop in a polyethylene (PE) matrix were studied at high temperatures under simple shear flow using a specially designed transparent Couette device. Twomain breakup modes were observed:(a) erosion from the surface of the drop in the form of thin ribbons and streams ofdroplets and (b) drop elongation and drop breakup along the axis perpendicular tothe velocity direction. This is the first time drop breakup mechanism (a),"erosion," has been visualized in polymer systems. The breakup occurs even when the viscosity ratio (eta_r) is greater than 3.5,although it has beenreporte dthat breakup is impossible at these high viscosity ratios in Newtonian systems. The breakup of a polymer drop ina polymer matrix cannot be described by Capillary number and viscosity ratio onlyit is also controlled by shear rate,temperature,elasticity and other polymer blending parameters. A pseudo first order decay model was used to described the erosion pheomenon and it fits the experimentla data well.