Study on the structure and properties of modified silk with ultraviolet absorbent北大核心CSCD

The silk fiber has an irreplaceable position in textile fibers and related silk fabrics have the advantages of light and airy texture good moisture absorption and breathability comfort in wear etc. It is also widely used in other fields such as the biomedical sector. However silk also has its own limitations poor light resistance and susceptibility to ultraviolet light especially the ultraviolet light of 290-400 nm wavelength in daylight such as under which condition it is prone to yellowing and photodegradation. The yellowing of silk is due to the photo-oxidation of tyrosine and tryptophan in silk protein under the action of ultraviolet light from sunlight and due to the production of yellow substances which affects the whiteness of silk. In addition from the molecular structure of silk most of the amino acids susceptible to UV light are distributed in the amorphous region. As the amorphous region is affected the structure of the crystalline region is also gradually relaxed the local degradation begins and the silk protein macromolecule chain is cleaved which leads to the decrease of the mechanical properties of silk fibers and accelerates the aging of silk fibers and fabrics. Therefore it is necessary to modify the silk products outside the anti-purple line. The current methods used to modify silk are mostly for post finishing modification including coating impregnation and chemical grafting methods but these methods often affect the original color or feel of the fabric and the durability of the modified effect is also poor. The feeding method is a green method to obtain modified silk by spraying mulberry leaves or artificial feed mixed with modifier which is ingested by silkworm and transferred to silk gland. In this study five aminobenzene UV absorbers were used as exogenous additive food for silkworms. The effect of molecular polarity on the transport of modifiers to silk glands was investigated and their effects on silkworm development and silk structural properties were studied. It was found that the aminobenzene UV absorbers were more easily transferred to the central silk gland silk glue and less to the posterior silk gland (fibroin). 4-dimethylaminobenzoic acid was found to be the highest in the posterior silk gland with a content of 3. 27 μg / strip. The cocoon width and cocoon quality of this group were significantly lower than those of the control group and the silk gum content was increased when this group was used as the study object. Compared with the control group the relative content of β-folded structure and crystallinity of the silk in the addition feeding group decreased slightly. The silkworm silk in the feeding group showed a certain UV absorption ability. After 330 h UV irradiation the breaking strength and elongation of the control group decreased by 48. 95% and 43. 52% respectively while those of the feeding group decreased by 42. 03% and 34. 18% respectively. In this paper UV absorbers were added to silkworms to obtain modified silk mainly focusing on the transfer of the modifier to the silk gland and the structural properties of the modified silk only for the most UV absorbers to enter the silk gland of the posterior group of silk. Other properties of the modified silk such as washing resistance have not been studied and some more in-depth studies are required. For instance it needs to be studied in depth for the limited absorption of exogenous additives by silkworms additive food's being not always absorbed by silkworms and transferred to the silk gland and the mechanism of action between the additive food and silk protein after the former's entering the silk gland. © 2022 Authors. All rights reserved.