| Electrospinning technique, by which electrostatic forces are employed to control the formation of fibers, is an attractive method that can readily produce fibers with diameters ranging from scores of nanometers to several micrometers from both natural and synthetic polymers. Electrospun regenerated silk fibers are characterized by small diameter and high specific surface area. Besides, with good biocompatibility and degradability, electrospun regenerated silk fiber mat can be used as ideal candidates for tissue-engineered scaffolds, wound dressings and drug delivery systems. Since the structure stability of the electrospun regenerated silk fiber mat is poor, the mat will easily dissolve and shrink when put into water, which limits its potential applications in many aspects.With excellent structural, mechanical, chemical, thermal, optical and electrical properties, the carbon nanotubes (CNTs) have drawn many scientists'attentions since it was discovered. The low degree of crystallinity and poor mechanical properties of the original electrospun nanofiber limit its practical application, so the carbon nanotubes can be used as reinforcement in co-electrospun nanofibers, which can improve the performance of the electrospun nanofibers.In this paper, multi-walled carbon nanotubes (MWNTs) were used as a reinforcement in electrospun silk fibroin/MWNTs fibers and silk fibroin/MWNTs/ polyamide6/66 blended fibers. The structure and performance of these two blended fibers were investigated, as well as the influences of the concentration of MWNTs and alcohol vapor treatment on the structure and performance of the blended nanofibers.The relationship between the concentration of MWNTs and the structure and performance of silk fibroin/MWNTs composite fiber:It is found that, between MWNTs and silk matrix a certain chemical bond was formed, which would improve the reinforcement. With the increase of MWNTs, the internal structure of the composite fiber was improved, but the diameter of fiber decreased. When the concentration of the MWNTs was less than 1%, the fracture strength and initial modulus of composite fiber mat were increased significantly with the increasing concentration of MWNTs. But if the mass fraction of MWNTs is too high, the mechanical property will deteriorate. The breaking elongation had no obvious correlation with the concentration of MWNTs.The relationship between the concentration of MWNTs and the structure and performance of silk fibroin/MWNTs/polyamine 6/66 composite fiber:Nanofibers with diameter under 100nm can be electrospun with the addition of MWNTs into the spinning solution, and the diameter decreased with the increase of MWNTs. Within a certain range of the concentration of MWNTs, both the degree of crystallinity (the concentration of MWNTs≤1.5%) and the mechanical properties(the concentration of MWNTs≤0.9%) were improved with the increase of MWNTs. The thermal stability of the composite fiber was improved steadily.The effects of ethanol vapor treatment on the structure and properties of composite fibers:The results showed that no remarkable morphological and crystal changes occurred during vapor treatment, and the thermal stability was slightly improved. The treatment affected mechanical properties greatly, which mean that the fracture strength and initial modulus of composite fiber mat were highly improved. But there was no brittlement emerged in the nanofiber mat after the treatment.After vapor treatment, the silk fibroin/MWNTs/polyamine 6/66 blended fibers with low concentration of MWNTs exhibited swelling and conglutination, and the fiber with higher concentration presented only radial expansion. The increase in the degree of crystallinity and thermal stability manifested that mechanical properties were improved after treated by ethanol vapor. Therefore the breaking strength, initial modulus and breaking elongation were all raised, indicating that ethanol vapor treatment was an effective way to improve the structure and performance of electrospun nanofibers.
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