Study on the matrix-fibril morphologies of polypropylene/polystyrene blends under non-isothermal uniaxial elongational flow

Abstract

Polypropylene/polystyrene blends with different viscosity ratios, p, ranging from 1.6×10−2 to 10.8, were prepared by using textile-grade isotactic polypropylene (iPP) and five kinds of atactic polystyrene (aPS), named PS1, PS2, PS3, PS31 and PS46 with different molecular weight, and then melt-spun into composite fibers with matrix-fibril morphology at different take-up velocities, v L , ranging from 125 to 1000 m/min. The effects of p on the diameters and quantities of dispersed droplets in extrudate fibers, and the effects of p and v L on the size and quantities of fibrils in take-up fibers were discussed, respectively. Based on a quantitatively characterization for the coalescence and deformation of droplets during melt spinning, a theoretical analysis based on Newtonian fluids simplification and the deformation theory was presented to predict the deformation and breakup of droplets during melt spinning. It is found that there is a good fit between theoretical and observed experimental results at most discussed take-up velocities. Furthermore, the uncertainties of Newtonian fluids simplification and a hypothesis of local energy dissipation from migration and coalescence were noted to explain the deviations between predicted and experimental data.