湿纺凝固负拉伸对初生纤维结构与性能的影响

研究了凝固负拉伸对聚丙烯腈(PAN)纺丝液的膨胀效应、初生纤维聚集态结构和性能的影响,初步揭示了膨胀效应和凝固取向的产生机理及其对初生纤维结构与性能的影响;指出溶剂与水之间的传质速率差是控制初生纤维结构进而控制其性能的最关键因素,它决定了原液细流表面凝固层的组成及结构,而凝固速率反映了凝固层的生长速度。研究发现:随着凝固负拉伸的降低,PAN纺丝液的挤出胀大比减小,其传质速率差与凝固速率均下降,初生纤维的凝固取向、结晶度和晶粒尺寸均增加,其截面形状趋于圆形,内部结构变得均匀致密、缺陷减少,从而使断裂强度得以提高。

Effect of Jet Stretch Ratio on the Microstructure and Properties of Protofibers by Wet-Spinning

In this paper, the effect of the jet stretch ratio on the extrusion die-swell effect (Barus effect) of polyacrylonitrile spinning dope and the aggregating structure and properties of the protofibers was systematically analyzed. It revealed the formation mechanism of the die-swell effect and spin orientation and its influences on the structure and properties of the protofibers. It showed that the mass transfer difference between solvent and non-solvent is the only key factor controlling the microstructure and composition of the coagulating layer and the coagulation rate reflects the growth rate of the layer. With the decrease of the jet stretch ratio, the extrusion die-swell ratio of polyacrylonitrile spinning dope becomes smaller, the spin orientation degree, the crystallinity degree and the crystal size all increase respectively, and the cross-sectional shapes become circular and the microstructure compact and homogeneous. As a result, the breaking tenacity of the profibers and resultant precursors all increased.