Analysis of Multiple Melting of High-Speed Melt Spun Polylactide Fibers Based on Kinetic Modeling

摘要

Multiple melting behavior of high-speed melt-spun polylactide (PLA) fibers was investigated by temperature modulated differential scanning calorimetry (TMDSC) in the heating process with various modulation periods in the calorimeter. In the case of the as-spun PLA fibers taken-up at 1km/min, a melting endothermic peak and a recrystallization exothermic peak appeared at the same peak temperature of 151 degrees C in the reversing and non-reversing heat flows (RHF and NRHF), respectively, whereas at 168 degrees C, an endothermic peak was observed in both the RHF and NRHF. On the other hand, the as-spun PLA fibers taken-up at a high-speed of 6km/min showed the melting in both the RHF and NRHF, but the recrystallization behavior was not obvious in the NRHF at the shorter modulation period conditions. The obtained data were analyzed based on the kinetic modeling of melting proposed by Toda etal. The real and imaginary parts of the complex apparent heat capacity in the melting region showed a strong modulation period dependence for both the low- and high-speed spun fibers. The endothermic heat flow of melting was separated by extrapolating the frequency to zero. For the PLA fibers spun at 1km/min, a set of melting and recrystallization peaks in the RHF and NRHF appeared even for the melting at 168 degrees C. In other words, the simultaneous occurrence of melting and recrystallization was confirmed through this extrapolation. For the 6km/min PLA fibers, the presence of an exothermic heat of recrystallization was clearly confirmed at a peak temperature of 164 degrees C.