SEGMENTAL AND CHAIN ORIENTATIONAL BEHAVIOR OF SPANDEX FIBERS

The internal structure and orientation behavior of two series of spand ex fibers, which were made with different spinning methods and differe nt soft and hard segment types, were studied by FTIR (Fourier Transfor m Infrared Spectroscopy), polarizing light microscopy, and Instron. Th e orientation behavior of hard and soft segments was studied with FTIR and those of polymeric chains with polarizing microscopy while the fi bers were being stretched by the mechanical stretcher. The orientation behavior of dry-spun fibers was observed to be very different from th at of the melt-spun fibers, which may be explained in terms of the int ernal structural difference such as the degree of phase separation and mechanical stability of the hard domains between the two types of fib ers. In general, the dry-spun fibers showed better elastic recovery pr operty than the melt-spun fibers. Since the polymer for the dry-spun f ibers was synthesized with ethylene diamine as a chain extender result ing in the urea groups in the hard segments, it forms more stable hard domain due to the high cohesion energy between the urea groups. The c hange of the birefringence values during the cyclic deformation was st udied with the polarizing light microscopy. The birefringence behavior s of the two dry-spun fibers were similar, whereas there was a noticea ble difference between the two melt-spun fibers. The difference was ex plained in terms of the effect of crosslinking agent in one of the mel t-spun fibers, which can stabilize the hard domain structure against t he external stress. Mechanical hysteresis values measured gave results consistent with those of FTIR and birefringence measurements. (C) 199 7 John Wiley & Sons, Inc.