Effect of degumming ratio on wet spinning and post drawing performance of regenerated silk

Regenerated silk fiber has attracted considerable attention because of its good blood compatibility and cytocompatibility, and the advantages of regenerated fiber, such as control of structure and properties. In this study, wet spun regenerated silk fibers were fabricated by controlling degumming ratio and silk concentration. Rheometry, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to examine wet spinning and post drawing performance of silk. Dope solution viscosity was found to be a key factor determining the continuous fiber formation of silk and 0.07 Pa·s was essential for continuous fiber formation. Maximum draw ratio of the as-spun silk fiber was strongly affected by two factors: (1) crystallinity index from FTIR spectroscopy and (2) degumming ratio of silk. XRD of the wet spun silk fibers was not changed by the degumming ratio, silk concentration, and draw ratio. However, the crystallinity indices from FTIR were changed by these factors. Drawing-induced short-range crystallites of the silk were proposed based on FTIR and XRD. These results also show that XRD and FTIR can be used to characterize the micro-structure of silk complementarily because of their different detection characteristics: XRD and FTIR spectroscopy are sensitive to the detection of long- and short-range ordered crystallites of silk, respectively.