Poly(L-lactic acid)/poly(D-lactic acid) (PLLA/PDLA) as-spun fibers were prepared by melt spinning and drawn fibers were obtained by stretching the as-spun fibers at 60℃.The crystallization behavior of PLLA/PDLA fibers with different initial structure was investigated systematically with the combination of X-ray scattering

differential scanning calorimetry (DSC)

scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR).The key point was to clarify the effect of orientation on the crystallization transition of PLA fibers.The results indicated that orientation can induce the formation of the sc-crystals and increase the crystallinity of the PLLA/PDLA fibers.Furthermore

there was only the formation of sc-crystals during cooling process in the drawn fibers

while the -crystals appeared at 150℃ in the as-spun fibers.2D WAXS and FTIR results showed that the oriented sc-crystals hindered the formation of -crystals.Based on the above results

the highly-oriented PLLA/PDLA fibers containing pure sc-crystals with high crystallinity can be obtained by drawing the as-spun fibers at low temperatures and then annealing at a temperature above the melting point of -crystals.