Studies On The Structure And Properties Of Silk Treated With Ultra-low Temperature

Silk is a senior textile row material, with a soft and elegant luster, thin and soft,smooth texture, and has good strength, as natural protein fiber, the antistatic property,pilling resistance, moisture absorption, drape and skin affinity and other aspects arebetter than other fibers, by the vast number of consumers favor, It is considered as thebody of people is “the second skin”. But the fiber has poor light fastness, dyeing willappear gray injuries, and the utilization of reactive dye is not higher, and so on.At present, the research that to mulberry silk fiber’s heat treatment mainlycentrates on the aspect of high temperature, whereby the changes of structure andpeoperties after heat treatment with the fibers in sunshine, humidity, tension, additivesand other conditions, however, the research about the fibers under the cryogenictreatment is relatively less. This passage discuss the influence on structure andpropertyes with the freezing treatment that under low temperature.This passage is under different temperature conditions for ordinary degummedsilk deal with the freezing treatment, the scheme design of freezing treatment for thefiber moisture regain:5%~80%,the temperature of freezing processing:-10℃~-86℃，frozen processing time:1h~72h,treat the silk fiber with freezing processingexperiments, we can explore the influence of freeze process on fiber from two aspectsthat the structure and properties, specific conclusione as follows:Through the research about the structure of fiber with the freezing treatment, theresults show that, after the low temperature freezing treatment, there is hole andfissure structure phenomenon in fiber’s surface, it’s become significant with theincrease of moisture regain, freezing temperature drop, and the time of freezingextension, and the changes in local phenomenon. The fiber’s average roughness ofsurface Ra value and maximum height difference(P-V) value can be improved morethan5times than untreated fibers after freezing treatment, the surface area has2timesto improve. The characteristic peak to the direction of short wave in648cm-1afterfreezing, and the peak to long wave in1654cm-1of fiber, it shows that random coilsand a-helix structure of silk fibers tend to a more stable change of structure. Thediffraction peak raised in2°and10°of diffraction angle2θ,it shows that thecrystalline structure of fiber turn to a more stable Silk II type crystal structure, andwith the rise of moisture and the extension of freezing time, the fiber’s crystallinityincreased first and then decreased, when the frozen temperature decreases, the fiber’s crystallinity first decreased and then increased. Mulberry silk fiber’s maximum heatdecomposition temperature improve3.8℃than untreated fiber, and the enthalpy ofdecoumposition also improve25J/g,it shows that it is more structured of fiber’sinternal structure, fiber’s thermal stability improvement. Freezing treatment has noeffect on fiber’s density and diameter, it’s show that the fiber macromolecularextrusion deformation around the ice crystals when frozen, the size of “frozen hole” infiber after freezing is greater than the water molecules’s size, but this change do notspread to the whole fiber horizontally.Through the research about the performance of fiber with the freezing treatment,the results show that, fiber breaking strength decreases slightly, and strong damage inthe range of13%,but the elongation at break increased significantly, up to20%.thestrength less about10%than untreated fiber after100hours light, and it changesslowly of whiteness value and yellowness value, fiber light fastness improved.Afterfreezing treatment, fiber’s hygroscopic become strong, and with the moisture regainof fiber is higher, the lower freezing temperature, the longer processing time will be,the higher of the moisture of treated fiber. The dyeing performance of silk fiber willimprovement, using common Tracid brilliant red B dyeing, the rate of dying can beincreased by about10%,and the reactive dye Lanasol blue3G staining, the rate raiseabout27%,the rate of dye fixing increased14%,the total fixation rate increased35%,the rate of utilization improved greatly.