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Natural protein fiber is a kind of eco-friendly, skin-friendly natural biological composite material, mostly source from precious animal species. It has good elasticity, high moisture absorption, good warmth, and soft luster characteristics. Therefore, it has been widely used in the high-end textiles. Our country has a large number of protein fiber materials, however, the wearability and price are largely depend on the fiber fineness. The finer the fiber is, the better garment texture and higher price are. However, the production of natural protein fiber is low, which is far from being meet the actual demands, moreover, the price of natural protein fiber is rather expensive. Therefore, the use of physical and chemical methods to process the protein fiber into fine and Superfine fiber, not only can improve the added value of products to satisfy people’s comfort requirements, but also can in accordance with the concept of health protection of the ecological environment of mankind. Slenderizing technique is a kind of remarkable fineness, high production efficiency and low pollution method.On the basis of the slenderization technique, four kinds of natural protein fibers are choosed:mohair, alpaca, the Asian and European hair. In order to achieve the purposed effective pretreatment, the pretreatment agent should consist of reducing agent, wetting agent, bulking agent and high metal ion screening agent. The final stretched fibers are obtained through the specific pretreatment, proper stretching ratios and the later setting process.In order to investigate the micro structure of stretching-setting protein fibers, the analysis methods of FT-Raman spectrum and Infrared polarization spectrum are used. According to the analysis of the amide Ⅰ region, amide Ⅲ region and C—C skeleton vibration, especially, the processing for amide Ⅰ region by curve-fitting, which indicate that when the fibers are stretched, the transformation from α-helix to β-pleated occur, and β-turn plays an important role of secondary structure transition. When under high stretching ratio, the a-helix conformation content is almost no change, at this time the slippage of macromolecular structural block and matrix mainly occur, and the internal structure may be damaged, which result in the content of disordered structure increase. The analysis of cysteine oxide in S—O vibration area, prove that stretching leads to the breakage of the disulfide bonds.In the characterization of performance, fiber fineness, density, surface morphology (SEM), tensile strength and friction properties have been investigated. After modification by slenderization, fiber diameter is significantly thinner and the density increased first and then decreased. Fiber scales are damaged in different degree, in which the alpaca scales are damaged seriously. The length of scales were stretched longer, however the thickness became thinner. The strength of the fiber have a certain degree of improvement, which is closely related to the transformation of α→β conformation. The friction coefficient has been improved markedly, the "stic—slide" phenomenon exists in the sliding friction tests. Moreover, the directional frictional effect reducing (D.F.E.), which result in the fiber felting shrinkage improve effectively.
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