Dyeing properties of silk produced by silkworms reared on artificial and mulberry leaf diets

The dyeing properties were investigated for silk proteins produced by silkworms reared entirely on an artificial diet (A) and a mulberry leaf diet (M). The dyeing experiments were carried out with CI acid orange 7 at pH 3.9 and 60°C. The sericin contents of the A and the M raw silk samples were determined to be 26.0% and 23.7%, respectively. The equilibrium dye uptake and the dyeing rate of the A silk fibroin were almost the same as those of the M silk fibroin. The equilibrium dye uptake on each silk sericin was 3–4 times higher than that of the silk fibroin. On the other hand, the equilibrium dye uptake of the A silk sericin was higher than that of the M silk sericin, but the dyeing rate of the former was slower than that of the latter.     

Grafting of vinyl monomers onto silk using redox systems. Yellowing of silk

The aim of this study is to investigate the influence of temperature, initiator concentration, and vinyl monomer on silk yellowing during grafting. A series of silk fabrics was treated at four different temperatures (70, 75, 80, and 88°C), with different concentrations of initiator in the range 1–4% owf, with and without methacrylamide (MAA) or 2-hydroxyethyl methacrylate (HEMA). By treating silk with ammonium persulphate (APS), in the absence of a monomer, the degree of silk yellowing increased linearly with increasing both initiator concentration and treatment temperature, indicating that the initiator plays a specific role in enhancing silk yellowing through macroradical formation. The graft copolymerization of MAA (with APS as the initiator) caused only slight changes in the intensity of silk yellowing compared to blank-treated fabrics. On the other hand, the use of HEMA resulted in a deeper yellowing of silk fabrics, especially in the 70–80°C temperature range, due to its higher reactivity and to the tendency to form a homopolymer, leaving unreacted macroradicals on silk fibroin backbone. Compared to APS, other initiators, such as 2,2′-azobis(isobutyronitrile) (AIBN) and 2–2′-azobis-(2-amidino propane) dihydrochloride (ADC), caused a significantly lower degree of silk yellowing when tested in the absebce of a monomer. The yellowness of silk fabrics tended to increase by grafting with HEMA, while decreased by grafting with MAA. The use of variable amounts of monomer (25–150% owf) did not influence the degree of yellowing with ADC as the initiator. The results reported in this study show that the extent of yellowing induced on silk fabrics by grafting MAA and HEMA with APS as the initiator can be limited by a suitable selection of the processing parameters (initiator concentration, temperature). Moreover, the use of both AIBN and ADC appears promising, owing to their negligible effect on silk yellowing. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 239–246, 1998     

Silk grafting with methacrylic monomers: Process optimization and comparison

The process of silk weighting with methacrylamide (MAA) initiated by ammonium persulfate was studied to optimize the operating conditions to obtain high yields of grafted monomer. The influence of MAA concentration, liquor ratio, concentration of initiator, contact and heating time, acidification, and swelling agents were considered, and optimum operating conditions were outlined. Moreover, various monomethacrylates and dimethacrylates were grafted onto silk as alternative to methacrylamide. Most of these showed graft yields higher than MAA in the same operating conditions and some were found suitable for silk weighting since the weighted fibers show soft hand and good dyeing behavior. DSC and TGA analyses of grafted silk enabled to evaluate the influence of various monomers on the thermal behavior of the weighted fibers. Moreover, on the basis of DSC data, a correlation between the calculated enthalpy of grafted polyMAA and monomer content was studied. The molecular structure of silk grafted with methacrylic monomers was finally characterized by FTIR analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4039–4046, 2007     

Flow analysis of aqueous solution of silk fibroin in the spinneret of Bombyx mori silkworm by combination of viscosity measurement and finite element method calculation

Bombyx mori silk fibers possess outstanding mechanical properties in spite of being spun at room temperature and from the aqueous solution. Therefore, the mechanism of the structural transition has been studied with great attention, but still not be well understood. In this study the flow simulation of the silk fibroin aqueous solution using finite element method was performed on the basis of both the relationship between the viscosity and shear rate of the silk fibroin solution prepared from the silk gland, and the detailed structure of the spinneret including silk press part of the silkworm obtained from the optical micrographs. The viscosity of the silk fibroin solution decreased with power-law till the shear rate, about 1.5 s⁻¹ with increasing shear rate. Then the viscosity increased reversely which is speculated due to the fiber formation as a result of aggregation of the molecules. In the flow simulation analysis, the initiation site of the fiber formation was calculated by regulating the extrusion pressure. The fiber formation occurs in 550 μm from the spigot at 1 MPa and in 600 μm from the spigot at 50 MPa. The extrusion pressure in the range from 1 MPa to 50 MPa induces the fiber formation in the stiff plates (550-600 μm from the spigot), that is, the silk press part in the spinneret.     

The surface characterization of mulberry silk grafted with acrylamide by plasma copolymerization

The effects of plasma-induced graft copolymerization and simultaneous plasma-treated graft copolymerization with acrylamide (AAm) on the structure of mulberry silk are investigated. Through scanning electron microscopy, transmission infrared (IR), and attenuated total reflectance-IR and x-ray photoelectron spectroscopy (XPS) studies, changes of the surface morphology, structure, and composition are observed. The results show that plasma-induced graft copolymerization has more influence on the original structure of silk than does simultaneous plasma-treated graft copolymerization. The former brings the AAm branch polymer into the main chain of silk by the initiation of some kind of oxygen and nitrogen groups formed by the plasma, but the latter directly forms the AAm branch or cross-linking polymers with oxygen and nitrogen groups on the silk surface. This is the reason for the high elastic recovery angle of silk fabric modified by the two plasma graft copolymerizations. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1713–1717, 1997     

The light fading mechanism of dyes derived from rhubarb extract

The effect of relative humidity and mordanting on the fading kinetics and colour change of dyes derived from rhubarb extract on wool and silk has been investigated. Wool samples showed negligible change in colour even after 100 h of exposure, whereas silk samples became significantly darker. Relative humidity in the range of 10–45% and mordanting did not appear to affect the rate of fading on both the fibres. However, the rate and extent of change in colour (ΔE) on exposure was different for different mordants. The high resistance of the dye to light fading indicates that the dye is present in a highly aggregated form in silk and wool.     

Improving the photostability of bleached silk without reducing its whiteness

Bleached silk is rapidly yellowed by exposure to the ultraviolet radiation present in sunlight. The conventional application of a water‐soluble hydroxyphenyl benzotriazole ultraviolet absorber (such as UVFast W) to bleached silk reduces its rate of photoyellowing but has a negative impact on the whiteness of the bleached silk, largely cancelling out the improvements in whiteness achieved during bleaching. Therefore, a series of bleaching processes and aftertreatments using UVFast W on silk were investigated, with the measurement of reflection spectrum, whiteness, yellowness, and strength before and after exposure to ultraviolet radiation. The results show that whiteness of silk treated by oxidation–reduction double bleaching can be increased, and the whiteness of double‐bleached silk with 4% UVFast W aftertreatment was even slightly higher than that of the hydrogen‐peroxide‐bleached silk. After ultraviolet irradiation, double‐bleached silk samples with 4% UVFast W treatment resulted in both the highest whiteness and optimum photostability by comparison with unbleached standard silk and hydrogen‐peroxide‐bleached silk samples with and without 4% UVFast W treatment, and its strength difference was superior to the samples, except for standard silk with 4% UVFast W treatment after exposure to UV radiation for 18 h.     

Influence of swelling of noncrystalline regions in silk fibers on modification with methacrylamide

The degrees of swelling of noncrystalline regions of domestic and tussah silk fibers were investigated by measuring the small-angle X-ray scattering intensity of the fibers in wet conditions and analyzing the scattering intensity based on a two-phase model, i.e., crystalline regions and water-swollen noncrystalline regions. The influence of the degree of swelling of noncrystalline regions on the graft treatment of these fibers with methacrylamide was investigated. The changes in the structure caused by the graft treatment were also analyzed using the wide-angle X-ray diffraction measurements. As compared with the tussah silk fibers, the domestic silk fibers showed a larger degree of swelling of the noncrystalline regions, and gained a larger amount of resin by the graft treatment. The crystallites with smaller sizes in the tussah silk fibers were destroyed preferentially by the graft treatment. For the domestic silk fibers, the crystallites were destroyed more seriously and rather homogeneously independent of the crystallite sizes. © 1996 John Wiley & Sons, Inc.     

丝素蛋白微膜对花瓣生理影响分析研究

丝素蛋白的智能性水凝胶对采摘后玫瑰花瓣中过氧化物酶（ POD）,过氧化氢酶（ CAT）和超氧化物歧化酶（ SOD）的活性有着重要的影响。实验表明,涂抹了丝素的玫瑰花中POD、 CAT和SOD酶活性明显优于正常情况下玫瑰花中的酶活性,且其活性降低的趋势低于对照组,可见涂抹丝素对采摘后的玫瑰花具有延长保存时间的作用。本研究主要探究丝素对于玫瑰花的保鲜作用并初步确定对玫瑰花保鲜的最佳丝素浓度。     

Electrospinning and rheology of regenerated Bombyx mori silk fibroin aqueous solutions: The effects of pH and concentration

In this study, we prepared regenerated silk fibroin (RSF) aqueous solution to approach the environmental condition in the gland of silkworm, Bombyx mori. Then electrospinning technique was used to prepare the silk fibers. The results showed that pH and concentration had a remarkable influence on the properties of RSF aqueous solutions. With the increase in concentration and the decrease in pH, the rheological behavior of RSF aqueous solutions exhibited a transition from Newtonion fluid to non-Newtonion fluid. At the same time, lowering the pH could induce gel formation and decrease the electrospinnable concentration of RSF aqueous solutions. With the decrease in pH and concentration, the morphology of the electrospun silk fibers changed from belt-like shape to uniform cylinder. The conformation of the electrospun silk fibers was characterized by RS, WAXD and DSC. It was found that electrospun fibers were predominantly random coil/silk I conformation.     

棉织物丝素/TiO_2生态功能整理

用丝素蛋白整理棉织物,研究丝素蛋白降解时间及浓度对整理后棉织物性能的影响,确定最佳的丝素降解时间和浓度。在此基础上与TiO2复配,研究整理剂中TiO2含量对棉织物性能和结构的影响。结果表明:最佳丝素蛋白降解时间为120min,丝素浓度(质量分数)为1.63%;此时将丝素与TiO2复配,当TiO2质量分数为0.35%时,可使织物折皱回复角比纯丝素整理提高8.68%,紫外防护系数达到42.9,抗紫外性能达到二级。X射线衍射分析表明,丝素蛋白整理可降低棉纤维的结晶度,并使棉纤维由纤维素Ⅰ向纤维素Ⅱ转变,而TiO2整理可提高棉纤维的结晶度。     

Physical properties and structure of silk: 4. Spherulites grown from aqueous solution of silk fibroin

Spherulite formation in silk fibroin films cast from aqueous solution has been studied for crystallization conditions such as drying temperature, drying rate and pretreatment (freezing). Negatively birefringent spherulites in the α-form are observed in films cast between 0° and 40°C, and with a high drying rate at 20°C; positive β-form spherulites appear at higher temperatures up to 80°C and with a low drying rate at 20°C. Positive β-form spherulites are also obtained by freezing fibroin solution at ?2° to ?18°C and then drying at 20°C. It is found that positive β-form spherulites grow at 20°C on the surface of well-oriented β-form silk fibroin filaments (degummed silk) immersed in fibroin solution.     

丝纤维表面化学镀镍的研究

实验研究了丝纤维化学镀镍的操作方法、实验控制条件,讨论了各种因素对化学镀层的影响,试验了化学镀层与丝纤维的结合力,确定了丝纤维化学镀镍的工艺流程和最佳实验条件,实验结果表明,丝纤维经过预处理及敏化、活化处理后,化学镀镍溶液的pH值控制在8．0,镀镍温度在75℃,反应时间30min,可以得到较好丝纤维化学镀镍镀层。     

A kinetic and thermodynamic study of lac dye adsorption on silk yarn coated with microcrystalline chitosan

The coating of silk yarn with microcrystalline chitosan (MCCh) was carried out using the ultrasonic‐assisted method at a pulsed wave frequency of 80 kHz, which only had a slight impact on the yarn as measured by changes in Young's modulus and percentage of elongation compared with untreated silk. A significant enhancement of lac dye uptake onto MCCh‐coated silk yarn compared with the untreated silk was observed. The rate of dye uptake at different temperatures onto silk yarn coated with MCCh was investigated. It was found that the adsorption rate constant and diffusion coefficient both increased with increasing temperature, as a result of a diffusion kinetically controlled process with a diffusion activation energy of 9.40 kJ mol^?1. This suggests that dye adsorption on silk yarn coated with MCCh is a physisorption process. The free energy change (?G^○), enthalpy change (?H^○) and entropy change for dye adsorption were also determined, and the negative values of ?G^○ and ?H^○ obtained indicated that the lac dye adsorption process is both spontaneous and exothermic.     

The preparation of poly[N(n-butoxymethyl) methacrylamide] grafted silk fibers by polymerization using a low pH system

The graft polymerizations of the N(n-butoxymethyl) methacrylamide (BMA) monomer onto silk fibers were effected after reducing the pH of the grafting system to 2.5 by the addition of a formic acid solution. We compared the grafting efficiencies, surface characteristics, and thermal behaviors, as well as the whiteness levels and the extent of reduction of the rate of yellowing following UV irradiation, with the equivalent features of poly(BMA)-grafted silk fibers, prepared under normal (pH 6) conditions. The grafting efficiency [as poly(BMA) weight gain] onto silk fiber that was attained was almost 100% through optimization of the pH environment in the polymerization system by the addition of formic acid. The stiffness of the silk fabrics observed, following the conventional grafting, was markedly higher than that of equivalent silks after the polymerization at pH 2.5. The rates of yellowness index increase, for these latter silk fabrics following UV irradiation were also reduced, specifically in the initial irradiation period (up to 60 h). The SEM of the grafted silk fabrics reveal the absence of granules on the surface of the grafted silk fiber, when the silk was grafted with poly(BMA), after reducing the pH of the grafting system to 2.5. These findings suggest that the BMA monomer was polymerized specifically within the silk fiber and not on the surface. It is suggested that the increase in the polymer weight gain, and the reduced adverse effect on the fabric handle, arise because of the modified polymer location. © 1993 John Wiley & Sons, Inc.     

丝素蛋白在离子液体中的溶解特性研究

文章以离子液体为溶剂,研究了丝素蛋白在离子液体中的溶解特性。首先研究了丝素蛋白在不同结构的离子液体1-烯丙基-3-甲基咪唑氯化物（[AMIM]C1）和1-丁基-3_-甲基咪唑氯化物（[BMIM]c1）中的溶解速率和溶解度。结果发现,相同条件下,丝素蛋白在[AMIM]cl中具有较快的溶解速率和较大的溶解度;随温度的升高,溶解速度加快,合适的温度为95～105℃;随着丝素蛋白浓度的增大,相同条件下丝素蛋白在离子液体中的溶解速度减慢。XRD结果表明,丝素蛋白的非晶相部分首先被溶解,晶相部分结构被破坏后与溶剂作用逐渐被溶解。采用粘度法测定了丝素蛋白分子质量随溶解时间和温度的变化,结果表明：随加热时间增加和温度升高,蛋白质分子质量减小。为保证丝素蛋白的稳定性和溶解速率,温度一般控制在100℃以下,溶解时间小于5h。     

BmSuc1 Affects Silk Properties by Acting on Sericin1 in Bombyx mori

BmSuc1, a novel animal-type β-fructofuranosidase (β-FFase, EC 3.2.1.26) encoding gene, was cloned and identified for the first time in the silkworm, Bombyx mori. BmSuc1 was specifically and highly expressed in the midgut and silk gland of Bombyx mori. Until now, the function of BmSuc1 in the silk gland was unclear. In this study, it was found that the expression changes of BmSuc1 in the fifth instar silk gland were consistent with the growth rate of the silk gland. Next, with the aid of the CRISPR/Cas9 system, the BmSuc1 locus was genetically mutated, and homozygous mutant silkworm strains with truncated β-FFase (BmSUC1) proteins were established. BmSuc1 mutant larvae exhibited stunted growth and decreased body weight. Interestingly, the molecular weight of part of Sericin1 (Ser1) in the silk gland of the mutant silkworms was reduced. The knockout of BmSuc1 reduced the sericin content in the silkworm cocoon shell, and the mechanical properties of the mutant line silk fibers were also negatively affected. These results reveal that BmSUC1 is involved in the synthesis of Ser1 protein in silk glands and helps to maintain the homeostasis of silk protein content in silk fibers and the mechanical properties of silk fibers, laying a foundation for the study of BmSUC1 regulation of silk protein synthesis in silk glands.     

Grafting vinyl monomers onto silk fibers. II. Graft copolymerization of methyl methacrylate onto silk by hexavalent chromium ion

The feasibility of chromium(VI) to induce graft polymerization of methyl methacrylate onto silk was investigated. The rate of grafting was determined by varying monomer concentration, chromium(VI) concentration, temperature, acidity of the medium, nature of the silk, reaction medium, and redox system. The graft yield increased with increasing monomer concentration up to 0.65M, and with further increase of monomer the graft yield decreased. The graft yield increased with increasing chromium(VI) concentration. The grafting is considerably influenced by chemical modification of silk prior to grafting. The graft yield is influenced by thiourea concentration, decreasing with increasing thiourea concentration. The effect of certain inorganic salts and anionic surfactants on the rate of grafting was investigated.     

大叶榕榕树须总黄酮提取及对羟自由基清除作用

为充分利用大叶榕榕树须植物资源,避免资源的浪费,探讨大叶榕榕树须总黄酮的提取、鉴别方法及对羟自由基清除作用。采用超声波乙醇浸提法、超声波石油醚浸提法、超声波水浸提法分别从大叶榕榕树须中提取黄酮类物质,对所提取的黄酮类物质进行验证,并用紫外分光光度法测定含量。测得样品中总黄酮的含量分别为C=0.7240 mg/mL、0.5962 mg/mL、0.4529 mg/mL,回收率分别为101.0%、99.8%、100.9%,其纯度和产率均较高,其中,超声波乙醇浸提法产率最高。该提取液对Fenton体系产生的.OH自由基有很好的清除作用。该方法采用全物理过程,无任何污染,是提取大叶榕榕树须黄酮类物质的有效途径。大叶榕榕树须总黄酮有清除.OH自由基的作用。     

Physical properties and dyeability of silk fibers modified with ethoxyethylmethacrylate polymer

The structural characteristics, physical properties, and dyeing behavior of Bombyx mori silk fibers containing ethoxyethylmethacrylate (ETMA) polymer are reported in relation to the add-on. The add-on value increased with the reaction time and attained a maximum after 60 min at 80°C. The surface of silk fibers with an add-on value of 40% showed the presence of several irregular granules, consisting of ETMA oligomers. The infrared spectrum of the silk fibers containing the ETMA polymer showed overlapped absorption bands due to the molecular conformation of untreated silk and ETMA polymer, giving evidence that the ETMA polymerization occurred inside the fiber matrix. The DSC results suggested that the thermal decomposition behavior of the silk fiber remained almost unchanged, except that the decomposition temperature shifted slightly to higher temperature. The tensile properties of the silk fiber remained unchanged regardless of the ETMA polymerization. The rate and extent of acid dye uptake was greatly increased by the polymerization of ETMA into the silk fibers as well as the transfer printing properties.