Study on modification of rabbit hair fibers with L-cysteine

Rabbit hair fibers were modified by L-cystine under the action of ultrasound and a kind of modified rabbit hair fiber was obtained. An orthogonal test of four factors and three levels was designed. The range analysis was analyzed using a comprehensive score method of friction factor and fiber strength, and the variance analysis was carried out by Statistical Package for Social Science statistical software. The optimal modification conditions were obtained: a concentration of L-cystine (A) of 0.05 mol/L, ultrasonic power (B) of 90 W, a water bath temperature (C) of 75℃, and ultrasonic treatment time (D) of 1 hour. Univariate analysis showed the L-cystine concentration had the most significant effect on the modification of rabbit hair fibers, and the regression equation is y = 74.423 + 1300.267 A−1.818 C−9092A2 + 0.019C2. The surface brightness of the modified rabbit hair fibers was enhanced and the scale angle was increased 20° by setting up the angle of the scale model and the electron microscope. The internal structure of rabbit hair fibers was characterized by Fourier transform infrared spectroscopy, peak separation, and differential scanning calorimetry. The results showed that L-cystine reduced the disulfide bond in the macromolecular chain by 3%, resulting in a change in the secondary structure of the rabbit hair, a decrease in the α-helix structure content, and an increase in β-folding structure content. Ellman’s reagent was used to determine that the content of the sulfhydryl group consumed in the modification was 0.211 mol/L. Testing the dye adsorption capacity and spinnability (adding 20%) of modified rabbit hair fibers showed an obvious improvement.