Department of Chemistry, Faculty of Science, Mahidol University , Rama VI Road, Ratchathewi, Bangkok 10400 Thailand.
Langmuir. 2017 Jun 13;33(23):5872-5878. doi: 10.1021/acs.langmuir.7b01138. Epub 2017 May 26.
It has been challenging to separate oil from oil/water emulsions with droplet size less than 1 μm using conventional porous membranes. Membranes with small pores are preferred, but the trade-off is a dramatic reduction of volumetric flux. Here, we prepared membranes from electrospun polycaprolactone (PCL) fibers with high porosity (∼88%). When the membranes were stretched uniaxially at different strain levels, the pores became anisotropic with an aspect ratio (pore length/width) up to 5.3 ± 3.0. To improve their wettability, we added Tween 80, a hydrophilic surfactant, to PCL solutions for electrospinning. The modified PCL membranes showed excellent mechanical properties with a tensile strength at 6.59 ± 1.67 MPa and the elongation at break up to 130 ± 21%, warranting their use as free-standing separators. We narrowed the pore gap while maintaining the high porosity by stretching the membranes. Scanning electron microscopy (SEM) images of the stretched membranes show changes of pore geometry without altering the fiber size and fiber network integrity with strain up to 80%. The anisotropic membrane could exclude oil from oil-in-water emulsion droplets with a diameter as small as 18 nm without reduction of the volumetric flux in comparison with the nonstretched one.
使用传统的多孔膜从粒径小于 1μm 的油/水乳液中分离油一直具有挑战性。较小孔径的膜是首选,但代价是体积通量大幅降低。在这里,我们使用具有高孔隙率(约 88%)的静电纺聚己内酯(PCL)纤维制备了膜。当膜在不同应变水平下单向拉伸时,孔变得各向异性,纵横比(孔长度/宽度)高达 5.3±3.0。为了提高其润湿性,我们在纺丝溶液中添加了吐温 80,一种亲水表面活性剂。改性后的 PCL 膜具有出色的机械性能,拉伸强度为 6.59±1.67MPa,断裂伸长率高达 130±21%,保证了它们作为独立分离器的使用。我们通过拉伸膜来缩小孔径,同时保持高孔隙率。拉伸膜的扫描电子显微镜(SEM)图像显示,在应变高达 80%的情况下,孔几何形状发生了变化,而纤维尺寸和纤维网络完整性没有改变。与未拉伸的膜相比,各向异性膜可以排除直径小至 18nm 的油包水乳状液中的油,而不会降低体积通量。