Abstract:

In order to investigate the influence of degumming to silk dissolution and fibroin properties, silk degummed by Na2CO3 and urea was dissolved in CaCl2-CH3CH2OH-H2O ternary system, respectively. The degumming rate, structure of degummed silk, dissolution process and rheological property, film-forming and microsphere properties of fibroin were tested by color spectroscopy, fourier transform infrared spectrometer, X-ray diffraction, gel electrogphoresis, scanning electron microscope.  Results show that some fibroin will be dissolved in Na2CO3 degumming, resulting in a higher degumming rate, while the whiteness of silk degummed by Na2CO3 is lower, compared with urea degumming. In addition, Na2CO3 degumming had a great influence on the crystallinity of silk, and the heavy chain molecular unit of silk fibroin was damaged seriously in Na2CO3 degumming, facilitating the penetration of Ca2+ ion to fibroin to cause the degummed silk fiber easier to be dissolved. However, the molecular weight of silk fibroin is lower, and the structural viscosity of fibroin liquid is smaller, the mechanical properties and transmittance of silk fibroin membrane are reduced by Na2CO3 degumming process, and the particle size of blank microspheres from Na2CO3 degumming is smaller and the particle size distribution is more concentrated, compared with urea degumming.

Key words: silk, silk fibroin, degumming process, protein membrane, blank microsphere