Fine structure and physical properties of polyethylene/poly(ethylene terephthalate) bicomponent fibers in high-speed spinning. I. Polyethylene sheath/poly(ethylene terephthalate) core fibers

The high-speed melt spinning of sheath/core type bicomponent fibers was per formed and the change of fiber structure with increasing take-up velocity w as investigated. Two kinds of polyethylene, high density and linear low den sity (HDPE, LLDPE) with melt flow rates (MFR) of 11 and 50, [HDPE(11), LLDP E(50)], and poly(ethylene terephthalate) (PET) were selected and two sets o f sheath/core combinations [HDPE(11)/PET and LLDPE(50)/PET bicomponent fibe rs] were studied. The fiber structure formation and physical property effec ts on the take-up velocities were investigated with birefringence, wide-ang le X-ray diffraction, thermal analysis, tensile tests, and so forth. In the fiber structure formation of PE/PET, the PET component was developed but t he PE components were suppressed in high-speed spinning. The different kind s of PE had little affect on the fine structure formation of bicomponent fi bers. The difference in the mechanical properties of the bicomponent fiber with the MFR was very small. The instability of the interface was shown abo ve a take-up velocity of 4 km/min, where the orientation-induced crystalliz ation of PET started. LLDPE(50)/PET has a larger difference in intrinsic vi scosity and a higher stability of the interface compared to the HDPE(11)/PE T bicomponent fibers. (C) 2000 John Wiley & Sons, Inc.