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

Abstract

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 o 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.

Radial crystallization difference of melt‐spun polypropylene fiber along spinning line

“…It can also be seen that Δ X c increased along spinning line and reached the maximum value of 21.14% at the distance of 40 cm from the spinneret, and then Δ X c decreased along the spinning line. The profile of Δ X c versus distance from the spinneret is coincided to the profile of radial temperature gradient versus distance from spinneret which is similar to those in our previous study where the radial temperature gradient has the maximum value at the position of about 40 cm at the take up speed of 500 m min −1 . This confirms that the radial distribution of crystallinity of PP is depended on the radial temperature gradient of fiber during melt spinning.…”

“…Small differences in the structure of a polymer chain aggregation or morphology will result in huge differences in the performance of the products. Normally, the temperature, stress rate, and strain profile are not uniform in most of the melt processing, such as the parabolic shear profile in extrusion die flow and nonisothermal elongation during melt spinning. These processing history differences in very small domain result in the variety of microstructure and macrostructure of fibers.…”

Morphology Development of Polymer Blend Fibers along Spinning Line

“…However, a relatively uniform morphology was obtained in a matched viscosity ratio system (p ≈ 1) [64]. The dynamics of the melt spinning of PP/PS blend fibers showed that the polymer melt jets exit the spinneret at uniform temperatures [53]. As the polymer melt jets were drawn down, the polymer melt jets were cooled, with a temperature gradient in the radial direction of fiber.…”

“…The morphology development of polymer blend fibers during melt spinning is controlled by dynamic factors (e.g., elongational force and strain rate, which are mainly dependent on the take-up action) and thermal conditions (e.g., cooling system, which affects the heat conduction and transfer of polymer blend melts) [22]. Dynamic simulation studies [22,53,54] have shown that the axis velocity and stress of the filament increase gradually along the spinning line and continue until they almost reach the point of solidification, where the polymer blend fiber is converted from the molten to the solid state. This indicates that the second phase undergoes a gradually increased elongational force in the region between the spinneret and the solidification point.…”

Poly(glycolic acid) Nanofibers via Sea‐Island Melt‐Spinning

“…The principle of the sea‐island melt‐spinning has its roots in the morphology evolution of polymer blends in elongational flow . Specifically, the dispersed phase with initial dimension and shape is transformed into submicro‐ or nanofibers ( “island” ) in the matrix ( “sea” ) with the aid of melt or plastic flow .…”