Abstract
As conventional bleaching under alkaline conditions is chemically damaging to protein fibers, a three-stage protective bleaching process in neutral ethanol–water mixtures was proposed for camel hair using mordanting with ferrous salts, oxidative bleaching with hydrogen peroxide, and reductive bleaching with sodium hydrosulfite. The aim of this work was to improve the whiteness degree of camel hair without substantial tenacity loss. In addition, the roles of ethanol during the bleaching treatment were also examined by characterizing the fibers using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction. The whiteness degree and mechanical properties of camel hair bleached in the neutral ethanol–water system were significantly superior to those of fibers bleached by a conventional method. SEM images showed no visible cracks on the scales of fibers bleached in the ethanol–water system, whereas large grooves were observed on fibers bleached in aqueous solution. TEM images confirmed the positive influence of ethanol on the mordanting process, and FTIR spectra suggested that ethanol reduced the breakage of hydrogen bonds in the fibers during the oxidative bleaching process. These findings indicate the potential of this protective bleaching method for application to a broad range of other natural protein fibers.
Highlights
As an important class of specialty natural fiber, camel hair has distinctive characteristics, such as luster, softness, warmth, and natural colour [1,2,3]
These results indicate that the bleaching treatment in the ethanol–water system was more effective than that in the water system in terms of whiteness and weight loss values
To protect camel hair and enhance its whiteness degree during bleaching, the fibers were mordanted with ferrous sulfate heptahydrate and subjected to oxidative bleaching with hydrogen peroxide in a neutral ethanol–water system
Summary
As an important class of specialty natural fiber, camel hair has distinctive characteristics, such as luster, softness, warmth, and natural colour [1,2,3]. Owing to its exceptional temperature-regulating properties, camel hair is an ideal material for apparel applications. The demand for such rare animal fibers may increase as their use in some consumer items, such as high-grade fabrics, makes them more attractive [4]. Despite its small quantitative contribution, the significance of camel hair in the apparel and textile industry should not be underestimated. Camel hair is normally found in various shades of brown or gray; high levels of whiteness are essential for apparel fibers [5]. To achieve white or pastel colours, these fibers must be bleached to selectively decolorize the natural
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