title: Physical properties and dyeability of silk fibers degummed with citric acid.
abstract: Silk fibers from Bombyx mori silkworm was degummed with different concentration of citric acid, and the physical properties and fine structure were investigated to elucidate the effects of citric acid treatment. The silk sericin removal percentage was almost 100% after degumming with 30% citric acid which resulted in a total weight loss of 25.4% in the silk fibers. The surface morphology of silk fiber degummed with citric acid was very smooth and fine, showed perfect degumming like traditional soap-alkali method. The tensile strength of silk fiber was increased after degumming with citric acid (507MPa), where as the traditional soap-alkali method causes to decrease the strength about half of the control silk fiber (250MPa). The molecular conformation estimated by Fourier transform infrared spectroscopy and the crystalline structure evaluated from X-ray diffraction curve stayed unchanged regardless of the degumming with citric acid and soap. The dye uptake percentage of silk fiber degummed with citric acid decreased slightly, about 4.2%. On the other hand, the dye uptake percentage of silk degummed with soap was higher which indicates the disordering of the molecular orientation of the laterally ordered structure, accompanied with the partial hydrolysis of silk fibroin molecules by the alkali action of soap. The thermal properties were greatly enhanced by soap and citric acid degumming agents. Dynamic mechanical thermal analysis showed silk degummed with citric acid is more stable in higher temperature than that of soap. With heating at above 300 degrees C, the silk degummed with citric acid shows an increase in storage modulus and an onset of tan delta peaks at 325 degrees C and the melt flow of the sample was inhibited. The degumming of silk fibers with citric acid is safe and the results obtained are quite promising as a basis for possible future industrial application.
authors.affiliation: Department of Biosystems Engineering, University of Manitoba, Winnipeg, Manitoba, Canada R3T 5V6.
authors.forename: Majibur Rahman
authors.initials: MR
authors.lastname: Khan
authors.forename: Masuhiro
authors.initials: M
authors.lastname: Tsukada
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Gotoh
authors.forename: Hideaki
authors.initials: H
authors.lastname: Morikawa
authors.forename: Giuliano
authors.initials: G
authors.lastname: Freddi
authors.forename: Hideki
authors.initials: H
authors.lastname: Shiozaki
mesh_terms: D002152:Calorimetry, Differential Scanning; D019343:Citric Acid / Q000494:pharmacology*; D004396:Coloring Agents / Q000737:chemistry*; D055119:Elastic Modulus / Q000187:drug effects; D047030:Sericins / Q000302:isolation & purification; D047011:Silk / Q000737:chemistry* / Q000648:ultrastructure; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties / Q000187:drug effects; D013696:Temperature; D013718:Tensile Strength / Q000187:drug effects; D014961:X-Ray Diffraction
chemical_list: D004396:Coloring Agents; D047030:Sericins; D047011:Silk; D019343:Citric Acid