High Molecular Weight Silk Fibroin Used In Spinning

Silk has a unique performance. However, silkworm rearing requires a lot ofmanpower and time. Its high cost, relative to the industrial production of chemical fiber. Inview of this, it is important with water as a solvent. We simulate silkworm silk dryspinning using a high concentration of regenerated silk fibroin solution as a spinningsolution. However, at present the regenerated fibroin solution spinning is difficult. Solutionviscosity is too low.It is difficult to spun high strength regenerated silk. This may be dueto the silk fibroin was destroyed during regeneration. This article discusses the impact ofdifferent silk fibroin degumming methods and the resulting improved spinning process.In this paper, as a control, the0.05%Na2CO3conventional degumming methods, it isdegumming rate is21.6%. Electron microscope image shows the surface cracks. Althoughthis method can completely remove sericin, fibroin harm is relatively large, more severesurface corrosion. Viscosity of the regenerated silk fibroin solution is relatively low, andZetasizer particle shows size of3.1nm. Gel electrophoresis image shows most of fibroin Hchain molecule, L-chain and P25chains are degraded to smaller molecules fibroin. Whichsilk fibroin solution membrane make of degrades faster. So0.05%Na2CO3degummingmethod of preparation of silk fibroin poor spinnability, only the concentration is big (>20%) to be spun into yarn.This paper improves the degumming method. Degumming is by a lower pH ofNaHCO3.The results showed that degradation of fibroin was relatively small by themethod, but degumming rate is low at18%or less. Picric acid carmine detection showsdyeing silk surface is reddish. SEM images showed the presence of sericin. So NaHCO3degumming methods causes fibroin contains some sericin.On this basis, this article discusses the different pH degumming methods. UsingNaHCO3-Na2CO3buffer system, changes the pH from8.5to11. The results show that withthe increase of pH value. The rate degumming of silk increases, the degree of surfacedamage increases, molecular weight decreases. Particle size and viscosity decreases withincrease of pH value. Among degumming methods at pH8.5and9are incomplete removalof sericin, pH of9.5,10,10.5,11, degumming methods were complete removal of sericin.However, at pH10.5、11fibroin is corrosive relatively high. Therefore relatively ideal method of degumming is NaHCO3-Na2CO3buffer system of pH9.5. Silk surface is smoothafter degumming. Completing removal of sericin, but the molecular weight of the fibroin isrelatively small.Further, we improved degumming methods in this paper. The enzyme degummingstep was added after NaHCO3.degumming. Gel electrophoresis image shows fibroinmolecular weight is bigger by NaHCO3-papain degummed than pH9.5inNaHCO3-Na2CO3buffer solution. Viscosity increases, fibroin particle size is4.7nm.NaHCO3-alkaline protease degummed silk degumming rate is21.51%.The surface showsin yellow after the picric acid carmine staining. The results from scanning electronmicroscope showed that the glue was not attached to the surface,. That is the sericin wasdegummed completely from fiber.Further, the paper is adoption of NaHCO3-papaya enzyme degumming, showed notcontain sericin, and fibroin having relatively high molecular weight. Its degumming ratewas21.37%. After picric carmine dyeing surface is yellow, the presence of small surfacemolecules is hardly. Scanning electron microscopy showed that the surface is not attachedto the wire glue, no cracks appear. So degumming is more completely. Gel electrophoresisimage shows most of fibroin molecular weight is above150KDa, L-chain and P25chainsave relatively complete. Regenerated silk fibroin solution viscosity is relatively large. Thesize of fibroin molecules is into a normal distribution. Particle size is of5.1nm. Silk fibroinfilm by this degumming method shows slow degradation and good biocompatibility.Nano silk fiber was prepared by electrostatic spinning from silk fibroin solution. Theresults showed that fibroin solution obtained from0.05%Na2CO3unglued can not becomefiber when the mass concentration is below10wt%. Silk fibroin solution obtained fromNaHCO3-papaya enzyme degummed can obtained regenerated silk fiber at theconcentration of10wt%. The fiber diameter is about300-700nm, with the averagediameter is500nm.This study provides a basis for future studies in air dry spinning.