Study On The Preparation And Properties Of Two New Silk Derivatives

In this paper waste cocoon and waste silk (bombyx mori) were chosen as rawmaterial, their surfactant properties were studied on the basis of dissolved silk fibroin bythe means of etherification and salt-soluble. On the one hand, the active hydroxyl (-OH) ofsilk fibroin unit was replaced by sodium carboxymethyl (-CH2COONa) by theetherification reaction of silk fibroin and monochloroacetic acid, thus solublecarboxymethyl silk fibroin was composed. What’s more, the surfactivity propertiesincluding emulsification, emulsion stability, foaming, foam stability, surface tension andHLB value were determined. On the other hand, the silk fibroin was dissolved in calciumchloride solution through the methods of salt-soluble, its surfactivity properties wasdetermined and silk protein acid calcium were prepared.So waste cocoon and waste silkwere used efficiently, and it made the study of the surface-active properties of silk proteinpossible.The following several aspects were mainly researched in this thesis, the resultsfollowed:1. The preparation technology of carboxymethyl silk fibroin with the method ofpreparing carboxymethyl cellulose was established. Waste cocoon and silk were put in0.5%Na2CO3solution to boil and stoving after the impurity select. And then it basifiedwith ethanol aqueous solution. Then it etherified with chloroactic acid and washed thecrude product with ethanol solution. The final product was dried for4hours and finallythe carboxymethyl silk fibroin was obtained. Six factors of influencing on thecarboxymethyl silk fibroin etherification were studied, and the orthogonal test were didafter selecting the four factors which considerably influenced on the reaction. Theoptimum technological conditions were confirmed by the single factors and orthogonalexperiments in the preparation of carboxymethyl silk fibroin. The dosage of NaOH is7.2g,feeding ratio is2.2, the alkalized time is90min, etherified time is90min, alkalizedtemperature is25℃, etherified temperature is70℃.2. The surfactivity performance of carboxymethyl silk fibroin was studied in tia paper;the surface tension(γCMC) is51.37mN/m; The critical micelle concentration (CMC) is1.25g/L, HLB value is10, and it has good hydrophilic. The carboxymethyl silk fibroinsurfactivity performance is poorer on thickening performance, reducing the surfacetension, foaming ability, emulsification compared with carboxymethyl cellulose and sodium caseinate, and cannot completely replace them to become the new greenenvironmental protection products. However, it is necessary to be improved in terms ofperformance as much as possible.3. The new water-soluble silk fibroin preparation processes was established. Wastecocoon and silk were put in0.5%Na2CO3solution to boil and stoving after the impurityselect. The refined silk was put into the boiling l00mL concentration of30%-50%(W/W)CaCl2solution and the soluble time of calcium chloride was control. Then the silk proteinacid calcium was dialyzed for30h, the protein content in solution was detected using thetrace Kjeldahl method and the residues of calcium ions was detected usining EDTA. Thesilk protein acid calcium was obtained by freeze-drying of soluble silk fibroin afterdesalination. The figure of silk fibroin SDS-PAGE gel electrophoresis showed that itcomposed by multi-component and the molecular weight of silk protein acid calciumpresented a continuous distribution in a wider range. With the extension of the saltdissolved time, the molecular weight of silk fibroin decreased. But the trend of increasingmolecular weight was not very obvious along with the growth of salt soluble time. Thedialysis completed when the dialysis time was30h. The protein content of the silk proteinacid calcium solution was3.5%mainly and there was not much change.4. The surfactivity performance of silk protein acid calcium was studied in this paper.The emulsifying properties of silk protein acid calcium are good and have high emulsionstability. Silk protein acid calcium solution has certain foaming ability and the foamingstability is relatively stable. When the HLB value is10, silk protein calcium had betterhydrophilic. The critical micelle concentration is1.25g/L and the surface tension is61.37mN/m.