左旋聚乳酸纳米纤维膜的热处理研究

Heat-treatment of electrospun poly-L-lactic acid aligned nanofibrous membranes

研究了热牵伸和热定型处理对静电纺丝左旋聚乳酸平行纳米纤维膜力学性能和微观结构的影响。拉伸试验表明,在100℃热空气条件下,沿纤维排列方向上牵伸300%、热定型10 min的纤维膜力学性能最佳,其抗拉强度和模量分别达到103 MPa和1.83 GPa。扫描及透射电子显微镜观察显示,经热牵伸后,纤维的直径随牵伸率的增加而减小,其致密及平行程度相应提高,纤维内部转变为垂直于纤维轴且平行排列的片晶结构。差示扫描量热分析结果表明,纤维膜的结晶度随牵伸率的增加而增大,随热定型时间先增加后减小。广角X射线衍射和小角X射线散射分析可知,纤维膜经热处理后的结晶为α型,其微晶尺寸及晶面间距均随牵伸率的增加而减小,随热定型时间先增加后减小,而纤维内部的针状微缺陷随着牵伸率的增加而变得更加狭长有序,使得纤维膜的力学性能得以提高。

The effects of hot drawing and annealing on the mechanical properties and microstructures of parallel electrospun poly-L-lactic acid nanofibrous membranes（PLLA-ANM） have been systematically investigated by tensile tests,SEM,TEM,DSC,WAXD and SAXS.The maximum values of tensile strength and modulus of PLLA-ANM,103MPa and 1.83GPa respectively,were obtained when the membrane was hot stretched along the fiber axis by 300% at 100℃ and further annealed for 10min.The average fiber diameters of the PLLA-ANM decreased with increasing drawing ratio（DR）,but the fiber orientation was concomitantly improved.The structure of the as-spun membrane changed to the α-type,stacked-laminar crystalline structure after heat treatment.As the DR increased,the DSC crystallinity of the membranes increased,but the crystallite size along the（110/220） planes decreased.Both the DSC crystallinity and crystallite size of the heat-treated membrane initially increased and then decreased with increasing annealing time.In addition,the needle-like microvoids within the fibers became narrower and more ordered.