| Raw silk is a natural protein fiber, which is mainly composed of70%~75%fibroin and22%~24%sericin. Sericin that protects the fibroin is a gel protein with excellent moistureabsorption, antibacterial and oxidation resistance. And sericin can also reduce flexibility of rawsilk, while increasing rigidity, thus affecting knitting process. In order to be suitable for knittingprocess, raw silk need to improve its softness.This thesis mainly discusses the methods to improve softness of raw silk and its influencefactors, and provides guidance for producing raw silk with different softness requirements, basedon the principle of sericin protein degeneration, puffing, permeability and dissolution. Firstly,this paper uses two kinds of composite softening agent amino silicone oil SM-17and EKL-400to prepare soft raw silk, and analyses the effect of variety and concentration of softening agenton raw silk properties. Secondly, we choose SM-17, which performs a better softening property,to soak the raw silk. Then testing the performance of the osmosising treated silk and soakingtreated silk to explore the effect of softening methods on the properties of raw silk. Thirdly, weprepare three kinds of raw silk from hot air drying cocoon, frozen fresh cocoon and microwavetreated cocoon with different sericin structure, aiming at the effect of sericin structure on softnessand other properties of raw silk. The results show that:(1) Effects of variety and concentration of softening agent: Compared with conventionalraw silk, cohesion, strength and initial modulus of soft silk were decreased greatly, whilelubrication increased. It is found that varieties of softening agent have little effect on cohesionand lubrication of soft silk. Cohesion of soft silk decreased about27%, while lubricationincreased about7%. However, concentration of softening agent has great influence on tensilestrength and initial modulus. When treated by4.5g/L SM-17, raw silk’s strength decreased about32%, initial modulus decreased about38%, and it performs a better softness.(2) Effects of softening methods: Compared with conventional raw silk, the surface of soaking treated silk is more smooth and compact, the strength and elongation decreased, and theinitial modulus decreased about19%, while lubrication increased about4%. The surfacestructure of osmosising treated silk is looser, the strength decreased, the elongation increased,and the initial modulus decreased about37%, while lubrication increased about9%. Silkproduction process directly affects the distribution of sericin and penetration of soft agent. Softagent in soaking process mainly acts on the sericin outer of raw silk, while in osmosis processmainly acts on the sericin outer of cocoon filament. Both of these two kinds of silk can meet therequirements of knitting, but the raw silk treated by osmosis process performs better on softness.(3) Effects of sericin structure: Hot air drying cocoon breakage rate is35.7%, and itssurface is smooth. Frozen fresh cocoon breakage rate was3.3%. Since the sericin on its surfacepuffed too much, variously splitting and stripping occoured. Compared with hot air dryingcocoon, cohesion is decreased about7%, the mechanical properties increased, and lubricationincreased about17%. Microwave treated cocoon breakage rate is10%, and its surface is morerough. Compared with hot air drying cocoon, cohesion increased about4%, the mechanicalproperties improved significantly, while lubrication decreased about36%. The results showedthat: heat and moisture influence the sericin structure, and puffing degree greatly influences themechanical properties and cohesion of raw silk.Research results show that soft silk which meets the requirements of knitting process can beprepared by choosing cocoon with proper sericin puffing degree and using appropriate softeningagent in cocoon cooking. This process has swift flow, outstanding softening result. More over,the production properties are excellent. |
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