Study On The Modification Of Silk Protein Materials By Carbon Nanotubes

As a kind of protein fiber, silk is the only natural filament fiber that can be mass produced. Since the ancient times, because of the gorgeous appearance and soft texture, pure silk has been called "fiber queen". Silk has advantages of being nice and healthy to skin, while the antistatic property is poor. So, the improvement of the conductive properties of silk fiber and the antistatic properties of pure silk is very essential, and also can enlarge its application. In addition, the method which can efficiently strengthen regenerated fibroin fiber is needed to investigated because of the lower strength. Carbon nanotubes (CNTs), because of unique structure and excellent properties, such as mechanical properties, electrical properties, have a broad application prospect and are becoming the international research hot spots in the field of new materials. Therefore, considered the excellent properties, CNTs were taken to improve the conductive properties of silk fiber, the antistatic properties of pure silk, and the mechanical properties of regenerated fibroin fiber in this study. Finally, silk/CNTs conductive fiber, antistatic pure silk fabrics and enhanced CNTs/silk fibroin composite fiber were obtained.(1) The acid-oxidation-modification of CNTs using mixed vitriol/nitric acid solution. CNTs was characterized by infrared spectrum, X-ray diffraction (XRD), thermogravimetric (TG) analysis. The dispersity and dispersion stability of CNTs was also explored. The results show that concentrated acid is effective on the modification of CNTs. The acid oxidation treatment keeps the main structure of CNTs with new carboxyl and hydroxyl groups. After concentrated acid oxidation treatment, CNTs present good dispersion and thermal stability.(2) The modification of silk fiber by concentrated acid oxidative CNTs. Silk/CNTs conductive fiber was produced and the best preparation process was studied. The conductive fiber was characterized by SEM, infrared spectrum, X-ray diffraction (XRD), thermogravimetric (TG) analysis and its washing resistance, electrical properties, and mechanical properties were discussed. The results show that the best preparation process is:CNTs mass fraction0.08%, pH3.0, time1.5h, temperature70℃, bath ratio1:200. The volume resistivity of silk/CNTs conductive fiber in optimum process conditions decreases10magnitudes, while the conductive properties is greatly improved. Silk/CNTs fiber is found to have rough surface with evenly distributed CNTs, and greatly reduced crystallinity, slightly declined strength and elongation, slightly increased thermal stability, while prefect washing resistance. Anyway, silk/CNTs fiber meets the clothing requirements.(3) The antistatic finishing of pure silk by concentrated acid oxidative CNTs. The best finishing process conditions was discussed. The modified pure silk was characterized by SEM, infrared spectrum, X-ray diffraction (XRD), thermogravimetric (TG) analysis and its antistatic properties, washing resistance, crease-resist properties, and mechanical properties were analyzed. The results show that the best finishing process is:CNTs mass fraction0.04%, pH3.0, time1.5h, temperature80℃, bath ratio1:400. The antistatic properties of modified pure silk in optimum process conditions is greatly improved. Modified pure silk’s is rough with uniformly distributed CNTs on the surface. The crystallinity is compared to be declined without any new crystal structure, and thermal stability improved slightly. It shows good washing resistance and its crease-resist properties is improved to some extent. The breaking strength and elongation at break decreases slightly, but still keeps good overall.(4) The preparation of CNTs/silk fibroin composite fiber. The effects of temperature, storage time and the mass fraction of CNTs on rheological properties of spinning solution were discussed to get the best preparation process. The CNTs/silk fibroin composite fiber was characterized by SEM, infrared spectrum, X-ray diffraction (XRD), thermogravimetric (TG) analysis and its mechanical properties were investigated. The results show that the best preparation process is:silk protein concentration35%, temperature40℃, CNTs mass fraction1.0%and the longest storage time less than7days. The strength and elongation at break of CNTs/silk fibroin composite fiber in the best preparation process respectively increases by28.2%and22.4%than pure regenerated fibroin fiber, which indicates that CNTs could effectively enhance the mechanical properties of regenerated fibroin fiber. CNTs/silk fibroin composite fibers appear in grey with micro porous surface. It still owns the main crystal shape characteristics of fibroin and the thermal stability is effectively improved.