Human Hair Bleaching Technology And Its Mechanism Research

Human hair fiber as a kind of sustainable resources can be used as a biomass feedstock or directly used for making wigs.Bleaching plays the most important role in the process of reusing human hair fiber or putting it into pervasive applications.While in traditional bleaching technology,there are some disadvantages such as environmental pollution,incomplete bleaching,high cost and low strength.Herein,in order to find out the most appropriate age whose hair with the best comprehensive performance,the influences of age and bleaching on the whiteness and strength of human hair were observed.Furthermore,a series of research were extended for exploring the high efficiency bleaching technology.This thesis includes three aspects as followed:（1）The influence of the black hair fiber owners’age on the level of bleaching.The black hair fibers from people at the age of 5,26 and 45 were obtained to explore the differences of them in morphology,section,molecular structure,crystallinity and melanin granules by SEM,FTIR,XRD and TEM.The results shown that the hair fiber from people of 26 years old has the largest diameter,the highest crystallinity and small melanin granules.Meanwhile,the strength damage of the hair fiber caused by hydrogen peroxide bleaching was small and the bleaching effect was the best.Consequently,black hair fiber from 26 years old people was considered to be the best choice for bleaching and application.（2）The effect of DMAc/H₂O/LiCl solution system on bleaching of black human hair fiber.The DMAc/H₂O/LiCl system was used to replace the water system to bleach the black hair fiber.After bleaching,some important characteristics such as surface morphology,section bleaching morphology,transmission electron microscopy images,molecular structure,whiteness,strength and thermodynamic properties were compared between the original sample and the sample bleached in water system and DMAc/H2O/LiCl system respectively.The results shown that the swelling effect of DMAc/H₂O/LiCl system on cuticle layer results in best bleaching effect.The cuticle layer width of black human hair fiber enhanced from 2.47μm of water bleaching system to 5.11μm,increased by 106.9%.The lightness L*enhanced from 31.6 to 50.8,increased by 60.8%.Meanwhile,transmission electron microscopy images also proved that the decline of the number of melanin granules in DMAc/H₂O/LiCl system was obviously.Infrared analysis also presented that the sample bleached in DMAc/H₂O/LiCl system had the strongest cysteine peak at the 1040.3cm^-1 and the bleaching effect was optimal.Moreover,the mechanical properties also performed well,strength retention rate was high,storage modulus decreased and softness increased.From the above,the best bleaching conditions were determined as follow:the ratio of DMAc to H₂O was 6:4,the bleaching time was 30min,the concentration of FeSO₄ was 5g/L and the temperature was 75℃.（3）The effect of electrochemical conditions on the bleaching effect of black hair fiber.During studying the bleaching black hair in DMAc/H2O/LiCl system solution with additional electric field,hair fiber was housed on at the anode and reacted with hydrogen peroxide ions.The hydrogen peroxide ions decomposed from hydrogen peroxide and Meanwhile,active oxygen also been attracted to the anode.With the help of active oxygen and hydrogen peroxide ions,the whiteness and the bleaching efficiency of the black hair had a remarkable increase.The surface morphology,section bleaching morphology,transmission electron microscopy images,molecular structure,whiteness,strength and thermodynamic properties of the bleaching samples in DMAc/H2O/LiCl bleaching system and the same system with additional electric field were respectively tested to compare with the original sample.The results shown that the DMAc/H₂O/LiCl system with additional electric field had strongest power to damage the hair fibers’scale layer to get high whiteness and high strength retention rate.DSC/TGA shown that the residual mass of electrochemical bleaching sample is minimum,which mean that electrochemical bleaching was helpful to bleach black human hair fiber.All of the above work shown that the age of the hair owner had a prominent influence on the bleaching effects during bleaching the black human hair fiber.And DMAc/H2O/LiCl solution system provides efficient environment for bleaching human hair fiber.Moreover,electrochemical bleaching environmental conditions improved the efficiency further.This study provided an effective method for the bleaching black human hair fibers and offered basic research data for the reuse of these fibers.