Electrospun Silk Fibroin/Cellulose Acetate Blend Nanofibres: Structure and Properties

Silk fibroin (SF)/cellulose acetate (CA) blend nanofibres were prepared by electrospinning with 98% formic acid as a spinning solvent, and their structure and thermal properties were investigated by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The electro-spinnability of SF solution was remarkably improved with a small quantity of CA (not more than 10%), and the blend fibres were fine and uniform with the fibre diameters ranging from 50 nm to 300 nm. While adding 10% (by weight) CA into SF, the blends showed excellent spinnability without any beads or droplets in the surface of the electrospun mats under observation in large area, and the average diameter reached 142.1 nm. However, the spinnability of SF/CA deteriorated seriously when the content of CA was more than 30% (by weight), as the electrospun production of SF/CA blends were discontinuous and tacky with beads and dendritic structures. The results from FTIR, XRD and DSC showed that adding a small quantity of CA (not more than 10%) could induce the conformation transition of SF molecules from random coil to β-sheet. Accordingly, the thermal and mechanical properties were improved. Especially, the mechanical properties of the blend mats were greatly improved with the increasing of CA content from 5-10% (by weight). The blend nanofibre mats with 10% (by weight) CA content showed excellent mechanical properties, as the tensile stress and elongation-at-break reached 88.9 cN/mm2 and 12.77%, respectively. Nevertheless, the phase separation was observed between SF and CA in blend nanofibres when the content of CA was more than 30% (by weight).