Effects of coagulating conditions on the crystallinity, orientation and mechanical properties of regenerated cellulose fibers

Fabricating regenerated cellulose fibers using ionic liquids is a novel and green technology. Structural changes of regenerated fibers during forming process affect the macroscopic properties of regenerated fibers. The study of the regenerated fiber forming mechanisms in conditions relevant to fiber spinning processes, especially in the process of dry-wet spinning, is necessary and meaningful. In this work, regenerated cellulose fibers were prepared from wood pulp meal with 1-ethyl-3-methylimidazolium diethylphosphate ([Emim]DEP) under various coagulation bath compositions. The effect of coagulating conditions on the properties of regenerated fibers was investigated, and the internal structures and mechanical properties of regenerated fibers were characterized. The results indicated that regenerated cellulose fibers eventually developed differences in their internal structure and mechanical properties due to the different diffusion rates between spinning solution and coagulation bath. Ethanol significantly reduced the crystallinity and orientation, and elongation increased greatly. In addition, both the crystallinity and orientation of regenerated fibers increased with the decreased of ethanol content in coagulation bath when ethanol content >70 %, while the elongation was reversed. What's more, the scanning electron microscopy results revealed that the regenerated cellulose fibers' surfaces were homogeneous, indicating the regenerated fibers have great potential in the application of textile fabrics.