• Textile Coloration and Finishing
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• v.1 no.1
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• pp.1-6
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• 1989

The reaction of silk with a disulfide-containing crosslinking agent, i.e. bis($\beta$-isocyanatoethyl)disulfide(BIED), was studied in an attempt to obtain disulfide-crosslinked silk. The setting properties of disulfide-crosslinked silk fibers were studied. The permanent set values of single fibers were evaluated after the set fibers were relaxed in boiling water. When single fibers were set in boiling water or in boiling alkaline solution, the permanent set values of BIED-treated silk fibers were less than those of untreated silk fibers. When the fibers were treated with 2% thioglycolic acid solution at $60^\circ{C}$ followed by oxidation, settability of BIED-treated silk was better than that of untreated silk. The rearrangement of secondary bonds faciliated by cleavage of crosslinks as well as the rearrangement of crosslinks itself seems to be an important role in the set stability.

• International Journal of Industrial Entomology and Biomaterials
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• v.45 no.2
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• pp.70-77
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• 2022

Wet-spun regenerated silk fibroin (RSF) fibers have been extensively studied owing to their 1) useful properties as biomaterials, including good blood compatibility and cyto-compatibility; 2) the various methods available to control the structural characteristics and morphology of the fiber, and 3) the possibility of fabricating blended fibers and new material-embedded fibers. In this study, silk nanofibrils prepared using a new method were embedded in RSF to fabricate wet-spun silk nanofibril/RSF composite fibers. Up to 2% addition of silk nanofibril, the silk nanofibril/RSF dope solution showed slight shear thinning, and the G' and G" of the dope solution were similar. However, above 3% silk nanofibril content, the viscosity of the dope solution significantly increased. In addition, shear thinning was remarkably evident, and the G' of the dope solution was much higher than the G", indicating a very elastic state. As the silk nanofibril content was increased, the wet-spun silk nanofibril/RSF composite fiber became uneven, with a rough surface, and more beaded fibers were produced. Scanning electron microscopy observations revealed that the beaded fibers were attributed to the inhomogeneous dispersion and presence of agglomerates of the silk nanofibrils. As the silk nanofibril content and RSF concentration increased, the maximum draw ratio decreased, indicating the deterioration of the wet spinnability and post-drawing performance of silk nanofibril/RSF.

• Journal of Sericultural and Entomological Science
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• v.34 no.1
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• pp.49-56
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• 1992

Treatment of vinyl monomers onto silk fiber modifies the properties of the original silk fiber considerably. This field has been the subject of investigation by many workers using chemical and radiation initiation. Many studies on the reaction conditions, polymerization mechanism, physical properties and practical performances of methacrylamide-treated silk fiber have been continued. However, the polymerization mechanism has not been clearly revealed yet and this remains ambiguously whether the grafting is formed on fiber or not. In general, it has been accepted that free radicals were formed and vinyl monomers were polymerized in silk fibroin by graft polymerization mechanism, while active sties were varied by the types of monomer and initiator as well as by the reaction conditions. On the other hand, there is another argument on polymerization mechanism, in which monomers are polymerized and impregnated in the internal side of the fiber by homopolymerization. Though a large number of analytical methods are used to examine the polymerization mechanism of methacrylamide-treated silk fiber, the results on the basis of thermal analysis are merely reported in this paper. In differential scanning calorimetry (DSC) analysis, the thermal decomposition behaviors of the methacrylamie-treated silk fibers were determined and compared to those of the controlled silk fibers. DSC curves obtained from the methacrylamide-treated silk fibers showed double peaks at around 290$^{\circ}C$ (A peak) and 320$^{\circ}C$ (B peak) which are attributed to the thermal decomposition of the methacrylamide polymer and silk fibroin fiber, respectively. The temperature of A and B peak shifted to higher value with the increase of add-on. Also, the moisture regain of the treated silk fibers increased with add-on.

• Journal of Sericultural and Entomological Science
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• v.33 no.2
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• pp.82-86
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• 1991

The treatments of methacrylamide on silk fibers were studied in aqueous solution using potassium persulfate as an initiator, and suitable conditions of reaction were determined for weighing of silk fibers. The results obtained were summarized as follows ; The weight of MAA-treated silk fibers increased with monomer concentration. The adequate concentration of potassium persulfate was found to be 1.7%. Maximum weight increase was shown at initial pH 3.8 of reaction liquor controlled by buffer solution.

• International Journal of Industrial Entomology and Biomaterials
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• v.28 no.1
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• pp.19-24
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• 2014

Silk has always been one of the most favored textile materials. Fully degummed silk fiber (i.e., silk fibers without sericin) shows better luster than raw silk fiber (with sericin); it is also softer. On the other hand, raw silk fiber feels cooler because of the presence of sericin, making it useful as a textile for the summer season. Recently, partially degummed silk has attracted researchers' attention because it provides better luster, feel, and dyeing properties. However, the partial degumming of silk is very difficult because it results in inhomogeneously degummed fiber. In the present study, silk yarns were degummed with surfactant aqueous solutions and the effects of each surfactant on the degumming ratio, crystallinity, and homogeneity of the degummed silk yarn were examined. The degumming ratio and crystallinity index of silk yarn varied depending on the type of surfactant. On the whole, anionic surfactants resulted in higher degumming ratios and better homogeneity than nonionic surfactants.

• International Journal of Industrial Entomology and Biomaterials
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• v.26 no.2
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• pp.81-88
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• 2013

Wet-spun silk fibers have attracted the attention of many researchers because of 1) the unique properties of silk as a biomaterial, including good biocompatibility and cyto-compatability and 2) the various methods available to control the structure and properties of the fiber. Cellulose nanofibrils (CNFs) have typically been used as a reinforcing material for natural and synthetic polymers. In this study, CNF-embedded silk fibroin (SF) nanocomposite fibers were prepared for the first time. The effects of CNF content on the rheology of the dope solution and the characteristics of wet-spun CNF/SF composite fibers were also examined. A 5% SF formic acid solution that contained no CNFs showed nearly Newtonian fluid behavior, with slight shear thinning. However, after the addition of 1% CNFs, the viscosity of the dope solution increased significantly, and apparent shear thinning was observed. The maximum draw ratio of the CNF/SF composite fibers decreased as the CNF content increased. Interestingly, the crystallinity index for the silk in the CNF/SF fibers was sequentially reduced as the CNF content was increased. This phenomenon may be due to the fact that the CNFs prevent ${\beta}$-sheet crystallization of the SF by elimination of formic acid from the dope solution during the coagulation process. The CNF/SF composite fibers displayed a relatively smooth surface with stripes, at low magnification (${\times}500$). However, a rugged nanoscale surface was observed at high magnification (${\times}10,000$), and the surface roughness increased with the CNF content.

• Textile Coloration and Finishing
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• v.21 no.1
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• pp.67-72
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• 2009

To investigate the strong and effective sericin fixing agents and conditions, raw silk fibers were treated with the mixtures of urea-formalin, thiourea-formalin and melamine-formalin as sericin fixing agents, respectively. And the treated raw silk fibers were degummed by the degumming liquors of alkaline detergent and sodium carbonate to confirm the hardness of sericin fixation. The weight of raw silk fibers was decreased in the process of sericin fixation treating at 80$^{\circ}C$ for 60min. The effective sericin fixation was obtained by treating at $60{\sim}80^{\circ}C$ for 15min with the mixture of melamine and formalin. The mixture of melamine and formalin showed an outstanding ability of sericin fixation because the three amino groups of melamine were able to cross-link the hydroxy amino acids of sericin such as serine with the assistance of formalin.

• Journal of Sericultural and Entomological Science
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• v.37 no.1
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• pp.39-45
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• 1995

In this study the effects of methacrylamide-treatment on the physical properties and practical performances of silk were investigated for 38% MAA added silk fibers. The main results obtained were as follows; The values of tenacity, tearing strength, elongation, modulus and toughness decreased by the treatments of MAA on silk fibers. The moisture regain was increased by the MAA treatment, which improved the antistatic performance of silk fabrics. The stiffness values of MAA-treated silk fabrics increased and the performances of crease recovery were improved.

• International Journal of Industrial Entomology and Biomaterials
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• v.33 no.2
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• pp.132-137
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• 2016

Although silk textile shows excellent performance when used in clothing over a long period, its limited elongation and elasticity have restricted its extension to other textile and non-textile applications. In the present study, silk textile was produced using silk/polyurethane core-spun yarn and degummed to enhance its elongation and elasticity. The effects of degumming on the structure and mechanical properties of the silk textile were examined. Scanning electron microscopy observation revealed that the silk filaments became finer and more flexible with degumming, resulting in increased tangling of weft yarns and a highly shrunk textile structure in the weft direction. Although the strength of the degummed silk textile was decreased, its elongation greatly increased by 383% (a 16-fold increase) because of the degumming treatment. In particular, the elasticity of the silk textile was greatly improved. The silk textile exhibited ~30% reduction in the elongation after the second extension; however, the elongation almost did not change after 18 additional extension-recovery tests.

• Fibers and Polymers
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• v.7 no.2
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• pp.180-185
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• 2006

A pineapple protease, bromelain, was used to improve the dyeing properties of protein fibers such as wool and silk. The optimal condition for the activity of the pineapple protease was about $60^{\circ}C$ at pH 7. The wool and silk were treated with the protease extracted from a pineapple and the K/S values of the dyed wool and silk were measured using a spectrophotometer in order to compare the dye uptake. The protease treatment enhanced the dyeing properties of protein fibers without severe changes in mechanical properties. The surface appearances of protease-treated fibers were observed by microscopy.