HIGH-SPEED MELT-SPINNING OF SHEATH-CORE BICOMPONENT POLYESTER FIBERS - HIGH AND LOW-MOLECULAR-WEIGHT POLY(ETHYLENE-TEREPHTHALATE) SYSTEMS

Sheath-core bicomponent spinning of high molecular weight poly(ethylen e terephthalate) (HMPET, IV = 1.02 dl/g) and low molecular weight PET (LMPET, IV = 0.65 dl/g) is done at a take-up velocity range of 1 to 7 km/min. The structures of the individual components in the as-spun bic omponent fibers are characterized. Orientation and orientation-induced crystallization of the HMPET component are enhanced, while those of t he LMPET component are suppressed in comparison to corresponding singl e component spinning. Numerical simulation with the Newtonian model sh ows that elongational stress in the HMPET component is enhanced and th at of the LMPET decreases during high-speed bicomponent spinning. The difference in elongational viscosity is the main factor influencing th e mutual interaction between HMPET and LMPET, which in turn affect spi nline dynamics, solidification temperature, and structural development in high-speed bicomponent spinning. Simulation with an upper-convecte d Maxwell model shows that considerable stress relaxation can occur in the LMPET component if the HMPET component solidifies before LMPET. A mechanism for structural development is also proposed, based on the s imulation results and structural characterization data.