SYNOPSISHigh-speed bicomponent spinning of poly(ethy1ene terephthalate) (PET) (core) and polypropylene (PP) (sheath) was carried out and the structure development in the individual components, PET and PP, was investigated. The orientation and crystallinity development in the P E T component was enhanced as compared to that of the single-component spinning while the PP component remained in a low orientation state and had a pseudo-hexagonal crystal structure even at high take-up speeds. T o clarify the mutual interaction between the two components in bicomponent spinning, a semiquantitative numerical simulation was performed. The simulation results obtained using the Newtonian fluid model showed that the solidification stress in the P E T component was enhanced while that of the PP component was decreased in comparison with the corresponding single-component spinning. This is due to the difference in the temperature dependence of their elongational viscosity. Simulation with an upper-convected Maxwell model as the constitutive equation suggested that significant stress relaxation of the PP component can occur in the spinline if the PET component solidifies earlier than does PP. Based on the structural characterization results and the simulation results, it was concluded that the difference in the activation energy of the elongational viscosity and solidification temperature between the two polymers are the main factors influencing the mutual interaction in the bicomponent spinning process.
Sheath-core bicomponent spinning of high molecular weight poly(ethy1ene terephthalate) (HMPET, IV = 1.02 dllg) and low molecular weight PET (LMPET, IV = 0.65 dllg) is done at a take-up velocity range of 1 to 7 M r n i n . The structures of the individual components in the as-spun bicomponent fibers are characterized. Orientation and orientation-induced crystallization of the HMPET component are enhanced, while those of the LMPET component are suppressed in comparison to corresponding single component spinning. Numerical simulation with the Newtonian model shows that elongational Stress in the HMPET component is enhanced and that of the LMPET decreases during high-speed bicomponent spinning. The difference in elongational viscosity is the main factor influencing the mutual interaction between HMPET and LMPET, which in turn affect spinline dynamics, solidification temperature, and structural development in high-speed bicomponent spinning. Simulation with an upper-convected Maxwell model shows that considerable stress relaxation can qccur in the LMPET component if the HMPET component solidifies before LMPET. A mechanism for structural development is also proposed, based on the simulation results and structural characterization data.
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