取向对聚左旋乳酸/聚右旋乳酸复合物纤维结晶性能的影响

Effect of Orientation on the Crystallization Behavior of Poly( L-lactic acid) /Poly( D-lactic acid) Fibers

通过熔融纺丝的方法制备了PLLA/PDLA复合物初生纤维,在60℃拉伸获得高取向的牵伸纤维.采用X-ray散射为主要表征手段,结合差示扫描量热(DSC)、扫描电子显微镜(SEM)以及傅里叶变换红外光谱(FTIR)等技术,系统研究了不同初始结构的PLLA/PDLA复合物纤维在不同温度下的结晶行为,重点阐明了取向对PLA复合物纤维结晶结构的影响.结果表明,取向促进复合物纤维中立构晶的形成;将纤维升温至200℃停留3 min后,再进行降温,降温过程中,高度取向的牵伸纤维只有立构晶形成,而初生纤维则在150℃左右出现α晶,表明纤维中取向的立构晶会抑制α晶的形成.综合实验结果发现,通过低温牵伸初生纤维,然后高温(α晶熔点以上)退火,可制备出高取向且具有高立构晶含量的PLLA/PDLA复合物纤维.

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