关键词: 纳米颗粒, 添食育蚕, 蚕丝纤维, 染色性能, 染色动力学, 染色热力学

Abstract: Silk is a natural fiber with excellent performance, but it has the disadvantages of poor ultraviolet resistance, easiness of yellowing and poor mechanical properties. It is necessary to modify silk and give it better performance. Feeding silkworms with other diets can embed functional new materials into silk fibroin to form silk fibroin/functional composites, which is simple and effective. The existing research shows that feeding silkworms with other diets can affect the structure of silk and effectively improve the performance of silk. In the study of feeding silkworm with nanoparticles, the structure, thermodynamic properties and UV resistance of silk are mainly discussed. Dyeing performance is an important characteristic of fibers. At present, there are few discussions on the dyeing characteristics of modified silk.
To explore the dyeing properties of silk fibers modified by feeding silkworms with nanoparticles, nano-TiO2 and nano-CuO with a respective mass fraction of 2% were added to silkworms to obtain modified silk. Three acid dyes and three different types of reactive dyes were selected to dye the degummed silk fibers, and the dyeing rate, color depth and other indicators were measured. At the same time, the kinetic and thermodynamic mechanisms of silk fibers in acid orange II were explored. The experimental results show that the addition of nanoparticles can improve the dyeing properties of silk fibers: the dye uptake and apparent color depth (K/S value) of silk fibers modified by nano-TiO2 and nano-CuO are higher than those of the blank group. After 20 times of washing, the K/S value of the acid dyes and reactive dyes is still 1.5 and 2.0 higher than that of the blank group. It shows that the decrease of crystallinity of silk fibers caused by nanoparticle feeding can make more dyes enter the amorphous region to improve the dyeing performance of silk fibers. Dyeing kinetics and dyeing thermodynamics analysis show that the dyeing process of each group of silk fibers conforms to the pseudo-second-order adsorption kinetic equation and Langmuir adsorption. The dyeing process is an exothermic process, so it is more suitable for dyeing at lower temperatures. The actual adsorption equilibrium saturation of silk fibers modified with nano-TiO2 and nano-CuO at 60 °C is 0.14 g/kg and 1.04 g/kg higher than that of the blank group, respectively. The maximum value of the adsorbed dyes is 5.31 g/kg and 14.58 g/kg higher than that of the blank group, respectively. It shows that the modified silk fiber has better dyeing performance.
Through this study, the feasibility and effectiveness of feeding silkworms with nanoparticles are further illustrated. Adding nanoparticles can not only improve the mechanical properties of silk, but also improve the dyeing properties of silk. However, in this paper, only two kinds of nanoparticles were selected for feeding. The number and types of dyes were not enough. In the future research, it should be further discussed in order to provide a more complete theoretical and systematic study for the feeding method, and to provide a reference for the practical application of modified silk fibers.

Key words: nanoparticles, feeding silkworms, silk fiber, dyeing performance, dyeing kinetics, dyeing thermodynamics