Synthesis And Application Properties Of Silk Crosslinking Modifiers

Silk has excellent characteristics such as soft and lightweight texture,moisture absorption,breathability,and gorgeous appearance.However,silk fabrics are prone to wrinkle and affect their appearance during the wearing process,which is due to the fact that macromolecular segments in the amorphous region inside the fibers are prone to slip when subjected to external forces.Therefore,effective chemical crosslinking modification of silk fibers to reduce the relative slip of macromolecular chain segments is an effective method to improve the wrinkle resistance of silk fabrics at present.In the amorphous region of silk fiber,there are abundant tyrosine residue side chains,which are active groups for chemical modification of protein side chains.In this paper,a bisarylamino crosslinking agent A and a bismonochlorotriazinyl crosslinking agent B were designed,synthesized,and characterized as reactive groups,with a view to improving the wrinkle resistance of silk fabrics by covalent crosslinking of the two reactive groups with silk protein side chains.By means of various structural analysis methods,the mechanism of covalent crosslinking modification of the two reactive group crosslinking agents with silk protein side chains was revealed.The bisaryl primary amine crosslinking agent A based on Mannich reaction can modify silk under mild conditions.The results showed that when using 6%(o.w.f)self synthesized cross-linking agent A and crosslinking at pH 4.5 and 30 ℃ for 8hours,compared to the blank silk fabric sample without cross-linking agent treatment,the dry crease recovery angle of silk fabric improved by 35.2 ° and the wet crease recovery angle increased by 29 ° after crosslinking modification.Obviously,the crease resistance of silk fabrics has been significantly improved after Mannich reaction modification with a biaryl primary amine group crosslinking agent,and this crosslinking effect has a soap-resistant and wrinkle resistant effect,with little impact on the breaking strength and elongation of silk fabrics.Through infrared spectrum analysis of the cross-linked silk fabric,it was found that a ternary Mannich reaction occurred between the side chain of the tyrosine residue of silk protein and the aromatic primary amine group of crosslinking agent A,forming a covalent bond bond,and forming a cross-linking effect between adjacent or sufficiently distant segments of the silk protein molecule.Through TG,DSC and wearability tests,it was found that the decomposition temperature and heat resistance stability of the silk fabric after crosslinking modification were improved.By dissolving silk into a silk fibroin film and testing its physical properties and structure,it was found that compared to unmodified silk,the mechanical properties and water resistance of the modified silk fibroin film were improved to some extent,and the elongation at break did not decrease due to the increase in the degree of crosslinking;The structural changes of silk fibroin films were studied by means of infrared spectroscopy and thermal analysis.It was found that the amorphous structure of silk fibroin films made from modified silk was reduced,and the conformation of silk fibroin proteins was curled from random/ α-Spiral structure direction β-The folding structure changes,the structure tends to be regular and stable,and the thermal stability increases.The cross-linking effect of cross-linking agent A on silk fibers disappears without the dissolution of the fibers.Therefore,it is further proved that the strong covalent bond crosslinking between bisaryl-primary amine crosslinking agent A and macromolecular chains in silk fibers is the fundamental reason for improving its wrinkle resistance.Silk and cotton fabrics can be modified by crosslinking agent B using bismonochlorotriazine as a reactive group using reactive dyes for dye fixation.The experimental research shows that the crease recovery angle of the fabric after crosslinking modification is improved,and the dry crease recovery angle of silk is increased from 253.4 ° to 288 °,which is increased by 34.6 °.However,it has some impact on the mechanical properties of the fabric;The dry crease recovery angle of cotton fabrics increased from 143.8 ° to 171 °.When the amount of crosslinking agent was too large,the crease recovery ability of cotton fabrics decreased.The crosslinked fabric has a certain washing resistance.In addition,through the experiment of one bath dyeing with crosslinking agent B and reactive dyes,it was found that when dyeing with 2%(o.w.f)reactive blue EC-R in one bath,the effect on the color depth and color fastness of silk fabrics was small,and the color difference value of fabrics dyed with no crosslinking agent was lower than that of fabrics dyed with no crosslinking agent Δ E remains around 1;However,cotton fabrics are greatly affected,with a significant decrease in color depth and rubbing color fastness.Bischlorotriazine type crosslinking agent B is more suitable for use in silk fabrics.Through infrared spectroscopy and thermal analysis,it was found that monochlorotriazine type crosslinking agent B also covalently crosslinked silk fabrics in the amorphous region,similar to the binding method of reactive dyes.The active groups at both ends of the crosslinking agent reacted with the amino and hydroxyl groups on the silk,resulting in a cross-linking effect between the fibroin sub chains,which improved the structural stability and crease recovery of silk.In conclusion,by designing and synthesizing a biaromatic primary amine group crosslinking agent and a bismonochlorotriazine group crosslinking agent,they can be used for covalent crosslinking reactions with silk protein side chains,which can significantly improve the wrinkle resistance of silk fabrics.