Studies on melt spinning of sea-island fibers. II. Dynamics of melt spinning of polypropylene/polystyrene blend fibers

A two-dimensional (2-D) model for melt spinning of iPP/aPS blend fibers is proposed based on two-phase models on density and crystallinity and log-additive rule on elongational viscosity. A computer program is developed based on a hybrid method of fourth-order Runge-Kutta method and implicit Crank-Nicolson method to solve the model equations to obtain the axial profiles of fiber diameter, velocity, gradient of velocity and crystallinity, and the 2-D profiles of temperature, elongational viscosity and elongational stress. The simulated fiber diameters are compared with the measured diameters to verify the certainness of the simulation. The simulated results show that polymer melt jets solidify at the positions of about 40 cm beneath the spinneret which is verified by on-line measurement of fiber diameter. And the radial gradient of temperature, elongational viscosity and elongational stress reaches to 10 4 to 10 5 °C/m, 10 5 to 10 6 Pa·s/m and 10 5 to 10 6 Pa/m, respectively, at the discussed take-up velocities.