Abstract
We report the use of the DBU-CO2 switchable solvent system for the direct electrospinning of cellulose. Two cellulose types were investigated, i.e. microcrystalline cellulose (MCC) and cellulose pulp (CP). The morphologies of the obtained cellulose fibers were studied using scanning electron microscopy and optical microscopy. Results obtained showed that only particles with mean diameter about 1.2 μm could be obtained when MCC was used, even at high concentration (10 wt%). In the case of CP, an optimized concentration of 4 wt% resulted in standing fibers with a mean diameter of about 500nm. In order to improve the spinnability of the cellulose, different concentrations and ratios of PVA in combination with cellulose were investigated. The combination of cellulose (both MCC and CP) resulted in the formation of a unique fiber morphology, characterized by a homogeneous bead-like structure. An in-depth study of the fiber structure was carried out using Raman spectroscopy and showed that both cellulose and PVA were present in the formed beads. Finally, the challenge observed remained a complete removal of the solvents, which are not volatile enough, as well as explore a coagulation collection process for the fiber recovery in order to recover and re-use the employed solvent.Graphic abstract
Highlights
Bio-based raw material sources have gained global interest as a potential replacement for their fossilbased counterparts
In this report and based on our previous experiences working with the CO2-switchable solvent system for various cellulose valorization, we investigated the potential of this solvent system in the direct electrospinning of cellulose
Among the various factors playing a key role in the electrospinning process, the polymer molecular weight and the respective viscosity of the electrospinning solution are considered as the most critical ones
Summary
Bio-based raw material sources have gained global interest as a potential replacement for their fossilbased counterparts. Special solvents able to break this intra-inter hydrogen bonds are required to solubilize cellulose Examples such as N,N-dimethylacetamide-lithium chloride (DMAcLiCl), (McCormick and Dawsey 1990) N-methylmorpholine N-oxide (NMMO), (Fink et al 2001) dimethyl sulfoxide-tetramethyl ammonium fluoride (DMSOTBAF), (Heinze et al 2000) or trifloroacetic acid (TFA) (Hasegawa et al 1992). These solvents suffer from limitations including difficult recovery and/or toxicity and are not considered sustainable. DMAc-LiCl as well as NMMO/H2O was employed by Kim et al (2005, 2006) for direct electrospinning of cellulose to obtain sub-micron fibers with diameters ranging from 150 to 750 nm
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