The Properties Of Cocoon Silk In Guangxi Province

China is the birthplace of mulberry planting and silkworm rearing,and lays at the top of the world in the production,processing and trade of silk,which makes China in the dominant place in the international market.At present,the largest production base of silkworm mulberry at Guangxi province in China.The annual production of cocoons and cocoon silk accounts for 52%and 36%of the total production respectively.Therefore,understanding the structure and properties of cocoon silk of current silkwonn varieties in Guangxi province and funding out the difference between the silkworm varieties in Guangxi province and the silkworm varieties with high quality silk,which has practical significance to improve the breeding of mulberry silkwonn varieties and the quality of cocoon silk in Guangxi province.This paper by guangxi current silkworm varieties,such as "Liangguang NO.2","Guican NO.2","Guican N2","Huakang NO.2" and the national silk quality is excellent"Jingsonghaoyue" as the research object,the cocoon quality and silk,silk structure,thermal properties and mechanical performance of silk and silk detailed research by modern analytical techniques.And the difference and relation between cocoon properties of silkworm under different cocooning environmental humidities(RH 60%,RH 90%)were compared and studied.The aim is to provide some new ideas and methods for the breeding of silkworm varieties and the processing of cocoon silk.The main results of the study are as follows:(1)Cocooning in high humidity can increase dead silkworm rate and death-rate in silkworm cocoons,but the anti-NPV gene can not improve the tolerance of silkworm to high humidity.Moreover,high cocooning humidity can obviously reduce the robustness of silkworms before and after the cocoon battalion.In addition,the humidity in the cocoon-forming environment has no influence on the silk yield and silk volume of silkworm,but it can inhibit the water loss of silkworm pipa and affect other yield indexes.(2)Through the observation of cocoon layer and cocoon silk electron microscope,it is found that the cocoon layer density is higher under the high humidity environment,and the contact points are larger.So the gelatinization between cocoon filaments is enhanced,which leads to the decrease of the release rate of cocoon silk.(3)The proportion of the ?-conformation of the "Jingsonghaoyue" cocoon silk is more than that of other kinds of cocoon silk.In addition,the humidity of the cocoon has influence on the cocoon silk-folding conformation.When the cocooning environmental humidity is high,some cocoon cultivars can be induced to switch from a-helix and ?-turn to ?-sheet.(4)the thermal stability of cocoon silk of silkworm resistant to NPV is generally lower than that of ordinary silkworm,but the humidity of cocoon environment of silkworm has little influence on the thermal stability of cocoon silk.(5)The humidity in cocooning environment has great influence on the mechanical properties of cocoon silk and raw silk,and the cocooning humidity can increase the elongation of the cocoon silk and raw silk,but the influence on the strength and the tensile strength index is not obvious.During the high humidity environment cocooning,it not only improved the rigidity of the raw silk,such as "Guican NO.2","Guican N2","Huakang NO.2" and "Jingsonghaoyue",but also increased the toughness of the filaments,such as"Liangguang NO.2","Guican NO.2","Guican N2","Huakang NO.2" and "Jingsonghaoyue"In addition,the mechanical properties of raw silk of "Guican NO.2" and "Huakang NO.2" were improved completely when the cocoon humidity was 90%,the elongation,tensile strength,stiffness and toughness were improved in different degrees.